culture media research paper

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• New Microbes New Infect
• v.34; 2020 Mar

Bacterial culture through selective and non-selective conditions: the evolution of culture media in clinical microbiology

1) Aix-Marseille Univ, IRD, APHM, MEPHI, Marseille, France

J.C. Lagier

2) Institut Hospitalo-Universitaire Méditerranée Infection, Marseillle, France

S. Khelaifia

Microbiology has been largely developed thanks to the discovery and optimization of culture media. The first liquid artificial culture medium was created by Louis Pasteur in 1860. Previously, bacterial growth on daily materials such as some foods had been observed. These observations highlighted the importance of the bacteria's natural environment and their nutritional needs in the development of culture media for their isolation. A culture medium is essentially composed of basic elements (water, nutrients), to which must be added different growth factors that will be specific to each bacterium and necessary for their growth.

The evolution of bacterial culture through the media used for their culture began with the development of the first solid culture medium by Koch, allowing not only the production of bacterial colonies, but also the possibility of purifying a bacterial clone. The main gelling agent used in solid culture media is agar. However, some limits have been observed in the use of agar because of some extremely oxygen-sensitive bacteria that do not grow on agar media, and other alternatives were proposed and tested. Then, the discovery of antimicrobial agents and their specific targets prompted the emergence of selective media. These inhibiting agents make it possible to eliminate undesirable bacteria from the microbiota and select the bacteria desired. Thanks to a better knowledge of the bacterial environment, it will be possible to develop new culture media and new culture conditions, better adapted to certain fastidious bacteria that are difficult to isolate.

Introduction

The discovery of culture media allowed the development of microbiology in the nineteenth century [ 1 ]. Bacterial culture was the first method developed to study the human microbiota [ 2 ], using an artificial medium that allows growth and isolation of bacteria. The first to have cultured a bacterium in a reproducible way was Louis Pasteur in 1860 thanks to the development of the first so-called artificial culture medium [ 3 ]. Recently, after the emergence of molecular techniques in the 1970s, such as PCR, sequencing and more particularly metagenomics, microbiologists have favoured these innovative techniques to the detriment of culture. Nevertheless, metagenomics presents certain disadvantages and in particular a depth bias, due to the lack of sensitivity of the primers used, because it does not detect bacteria present at concentrations <10 5 bacteria per gram of stool [ 2 ]. Moreover, these techniques only detect DNA: it is impossible with these techniques to differentiate DNA belonging to living bacteria from that of the transient bacteria of the microbiota studied, or from that of dead bacteria.

A few years ago, culturomics, a new culture technique that uses a very large number of culture media and culture conditions to extend the repertoire of bacteria, was developed in our laboratory [ 2 ]. This technique demonstrates the complementarity between metagenomics and culturomics. Therefore, the metagenomic identification of bacterial species existing in a given microbiota can be exploited by culturomics through the optimization of new specific culture media for the isolation of these species. This complementarity allows culturomics to become a targeted technique.

New culture media today mimic the natural environment of bacteria by adding different elements in culture medium to cultivate bacteria that were previously uncultivated.

We propose here a bibliographical review of culture media and the evolution of techniques through the development of microbiology over time.

Empirical approach of microbiology

Observational microbiology.

Microbiology is defined not only by the organisms it studies, but also by the tools used to study them. The first observation of a bacterium was made around 1673 by the Dutch microscopist Anton van Leeuwenhoek thanks to the microscopes he had developed. Those enlarged from 50 to 300 times what he observed [ 1 , 3 ].

In the course of his research, he highlighted small structures that he called ‘animalcules’ [ 4 ], because he thought he was observing small animals [ 5 ]. Throughout his observations, he described and drew yeast cells, filiform fungi, microscopic algae and protozoa [ 4 ]. Leeuwenhoek was also the first to observe a parasite, Giardia lamblia [ 3 ]. However, microscopy alone cannot address all the questions about the microorganisms studied. For about 200 years microbiology was stagnating until the development of microbial isolation techniques in pure cultures. This is another important milestone in the history of microbiology.

Cultural microbiology

The birth of culture broth.

In the thirteenth century, 400 years before Leeuwenhoek, a blood-like substance appeared on the communion bread. In line with Christian beliefs, this red substance was assumed to be the blood of Christ. Bartholomeo Bizio, an Italian pharmacist, solved this mystery in 1817 thanks to advances in microbiology and showed that it was not blood, but a microorganism that he named Serratia marcescens . This bacterium appeared as red colonies on bread when stored in a warm and humid atmosphere [ 6 ]. It is one of the first natural cultures of a bacterium. The origins of culture media date back to the nineteenth century. Many bacteriologists have tried, with varying degrees of success, to grow bacteria on the food or material on which the microorganism was first developed.

Evolution of microbiology was made possible by challenging the theory of spontaneous generation, according to which living organisms could develop from dead or decaying matter and so spontaneously appear in cultures. Hence, it was inconceivable to obtain pure cultures. In 1861, Louis Pasteur, a French microbiologist [ 3 ], solved this problem through an experiment. He placed nutrient solutions in flasks, heated their necks with flame and stretched them in various ways, keeping the end open to the air. Pasteur boiled the solutions for a few minutes and cooled them. No growth appeared even if the contents of the flasks had been exposed to air. Pasteur noticed that there was no growth because dust and germs had been trapped on the walls of the curved tubes. If the tubes were broken, growth began immediately. In this way, Pasteur not only demonstrated that spontaneous generation was nonsense, but also found ways to keep sterile solutions [ 3 ].

The first to have cultured bacteria reproducibly in a liquid culture medium was Louis Pasteur. In 1860, he developed a culture medium containing ‘yeast soup’, ashes, sugar and ammonium salts [ 7 , 8 ]. His objective was to create a fermentation medium to demonstrate that each fermentation (alcoholic, acetic, lactic …) was associated with the development of a particular microorganism [ 9 ]. The presence of these different elements in the medium allowed him to observe that some of these components could promote or inhibit the growth of certain bacteria and that they could also allow the emergence of certain bacteria compared with others [ 8 ].

Indeed, in the course of the study of fermentation of beer, he was confronted with a problem: when the beer was healthy, the microscope only showed brewer's yeast, but when the beer was acid, Pasteur noticed that the tanks contained ‘tiny rod-shaped objects’ producing lactic acid. This fermentation medium therefore made it possible to highlight the multiplication of this bacterium [ 1 , 3 ].

In 1881, Robert Koch demonstrated optimal growth of bacteria when they were incubated in a broth composed of fresh beef serum or meat extract. However, the use of a liquid culture medium did not produce pure bacterial cultures. Koch therefore sought a way to solidify the medium [ 8 ] ( Fig. 1 ).

Evolution of culture media: from the first bacterial culture (1673) to culturomics.

Emergence of pure cultures in solid media

First, he tested coagulated egg albumin, starch paste or an aseptically cut slice of potato. However, not all of these techniques allowed him to isolate colonies. Koch then added gelatin to his broth and poured it all over a flat glass plate. However, gelatin had disadvantages as it liquefied at temperatures above 25°C and could be consumed by gelatinase, an enzyme produced by certain bacteria. Thanks to the wife of one of his assistants, Fannie Hesse, who used agar to solidify her jams, he replaced gelatin with agar, which allowed him to obtain firm agars and isolate bacteria. In 1887, Julius Richard Petri replaced the glass plate with a circular culture box, the Petri box was created, and is still used today [ 8 ]. This allowed him to obtain and observe isolated colonies and to limit contamination.

How to design an enriched culture medium?

An enriched culture medium is a medium to which have been added elements essential for the growth of bacteria.

The nutrients

In order to grow, bacteria need a minimum of nutrients: water, a carbon source, a nitrogen source and some mineral salts [ 10 ].

Water plays a fundamental role in solubilizing nutrients, transporting them and ensuring hydrolysis reactions. Some bacteria need free water for their growth. If evaporation occurs during the incubation of the agar, there may be a loss of this water, resulting in a decrease in colony size and inhibition of bacterial growth [ 10 , 11 ].

Carbon sources

Carbon is the most abundant constituent element in bacteria. It is essential for bacteria to produce carbon molecules, such as fats, carbohydrates, proteins and nucleic acids. Bacteria can use inorganic carbon sources, such as carbon dioxide, or organic sources such as sugars and alcohols [ 10 , 12 ].

Nitrogen sources

As for nitrogen sources, they are numerous and can be found in a large number of compounds used in the composition of a culture medium. It is found in the organic form, corresponding to protein hydrolysates, particularly in case of hydrolysate, proteose-peptone or tryptone [ 12 ], but also in an inorganic form, nitrates [ 13 ]. Nitrogen allows bacteria to synthesize their proteins.

Finally, among the common mineral salts, phosphate, sulphate, magnesium or calcium [ 11 ] are regularly found.

Energy sources

There are two types of bacteria, phototrophic bacteria, such as Thiocapsa roseopersicina [ 14 ], which uses light as an energy source by transforming it into an electrochemical gradient of protons [ 14 ], and chemotrophic bacteria, which use the energy of oxidation of mineral or organic compounds as energy sources [ 9 , 15 ]. Among these bacteria, we can find Listeria monocytogenes [ 16 ].

Growth factors

The use of a minimal medium does not allow the growth of certain bacteria that need specific elements to grow. It is sometimes necessary to add growth factors to culture media to boost the multiplication of bacteria. Growth factors are elements that bacteria are unable to synthesize from the nutrients available in the environment [ 10 , 17 ]. Growth factors are required in small quantities in the culture medium and their need is justified by the absence or blocking of a metabolic pathway in the bacterium.

Purine and pyrimidine bases

There are different categories of growth factors among which we find purine and pyrimidine bases. They are necessary for synthesis of nucleic acids. Indeed, some lactic acid bacteria need adenine, guanine, thymine or uracil for growth [ 17 ]. This is the case in particular for the bacterium Leuconostoc mesenteroides , for which guanine is essential for its growth [ 18 ].

Amino acids

Amino acids are also growth factors and are used for protein synthesis. Dunn et al. [ 19 ] showed in 1946 that only two amino acids were essential for Leuconostoc mesenteroides , glutamic acid and valine, whereas for Lactobacillus brevis , no less than 15 amino acids were necessary for its growth. This high requirement for amino acids can be explained by the fact that the base medium used at the time was not rich in common nutrients. Indeed, nowadays, Lactobacillus brevis grows on a COS agar (Columbia Blood Agar) (Biomérieux, Marcy l’Étoile, France), not supplemented with amino acids [ 20 ], but composed of casein hydrolysate and peptone proteose, themselves sources of amino acids [ 11 ].

Vitamins are also part of growth factors. They are coenzymes or precursors of coenzymes. A vitamin is an organic substance, necessary in small quantities for the metabolism of a living organism, which cannot be synthesized in sufficient quantity by that organism. Faecalibacterium prausnitzii , which is a fastidious bacterium, requires a large number of vitamins to grow, such as biotin, folic acid, riboflavin or vitamin B12 [ 21 ]. This bacterium also requires the presence of other growth factors such as volatile fatty acids (acetic acid, propionic acid or valeric acid) [ 21 ].

Blood use and its derivatives

Blood and its derivatives will also boost the growth of certain bacteria. In culture media, it is common to use sheep's blood or horse's blood. The role of blood is to act as a protective agent against toxic oxygen radicals [ 22 ], but also as a nutritional supplement. For instance, cooked sheep's blood provides the factor X (haem) necessary for the growth of many pathogenic species, including Haemophilus influenzae [ 23 ]. Most often, 5% blood is added to the culture media [ 22 ]. Serum, such as fetal calf or lamb serum, can also be used as a growth factor by providing a large number of elements such as lipids, vitamins, triglycerides, minerals and others [ 24 ]. This blood has been cleared of cells, platelets and clotting factors. Fetal calf serum, which is most commonly used in microbiology [ 25 , 26 ], must be inactivated by heat before use (56°C for 30 min) to inactivate all components of the complement system present in this serum [ 27 , 28 ]. It must be stored at –20°C and heated to room temperature rather than in a water bath to avoid deterioration of the proteins it contains.

Rumen fluid

Finally, it is also possible to use the rumen fluid [ 2 , 29 ] to promote the growth of certain bacterial species by mimicking their natural environment. The rumen fluid used corresponds to the rumen of the sheep. To prepare it, it is first necessary to recover the juice from the fermented plants in the stomach by filtering it through a fine cloth. This juice is then centrifuged (10 000 rpm for 90 min) and the supernatant is collected. Then, it undergoes three successive filtrations at 0.8 μm, 0.45 μm and 0.22 μm [ 2 , 30 ]. 5% rumen juice is usually added to the culture media. The rumen fluid can promote the growth of certain species of Treponema , such as Treponema hyodysenteriae and Treponema innocens [ 31 ].

Antioxidants

Some anaerobic bacteria are fastidious to grow and new culture strategies have been developed to isolate them. Indeed, anaerobic bacteria are most abundant in the human intestinal microbiota, accounting for up to 99.9% of total bacteria [ 32 ] and are extremely sensitive to oxygen, which is toxic to them. Antioxidants have therefore been added to culture media to allow the culture of strict anaerobic bacteria under aerobic conditions [ 33 , 34 ]. A number of antioxidants have been tested and have shown satisfactory results. This is the case for ascorbic acid and glutathione [ 34 ] or uric acid [ 35 ]. The addition of these antioxidants to the culture medium and its incubation under aerobic conditions allowed the growth of 135 strict anaerobic bacteria, 12 microaerophilic bacteria and 22 strict aerobic bacteria [ 35 ].

How can we have a selective culture medium?

A selective culture medium is used to isolate a particular bacterial species or genus. After the addition of a number of inhibitors to the culture medium, the objective of this type of medium is to eliminate unwanted microbial flora. The selective medium is composed of a basic medium to which antibiotics, chemicals, dyes, antiseptics, sodium salts or phages can be added [ 36 ].

Antibiotics

Antibiotics are the most commonly used selective agents. Their spectrum of action being well known, it is easier to anticipate their action on bacteria. There are a large number of antibiotics that can be used in culture media, some of which are called antibacterial because they target bacteria and others antifungal because they eliminate fungi and yeasts [ 37 ]. Some molecules target Gram-positive bacteria, such as penicillin G, bacitracin or vancomycin, whereas others target Gram-negative bacteria, such as colistin or polymixin B. Amphotericin B, cycloheximide or nystatin have an action against fungi and yeasts ( Table 1 ) [ 10 , 39 ]. Several antibiotics can be combined to obtain a more selective medium [ 37 ].

Table 1

Antibiotics agents used in bacterial culture

✓ Action against bacteria or fungi; χ No action against bacteria or fungi.

Antiseptics

Antiseptics are more rarely used in culture media. However, cetrimide [ 43 , 44 ] or acriflavin [ 10 ] can be found in some culture media. Chlorhexidine can be used to select Mycobacterium tuberculosis [ 45 , 46 ] ( Table 2 ). Ethanol can also select bacterial species, including sporulated bacteria [ 47 , 48 ] such as Clostridioides difficile [ 47 ].

Table 2

Antiseptics used in bacterial culture

Cetrimide Agar Base is a culture medium used to selectively isolate and identify Pseudomonas aeruginosa . Cetrimide is a quaternary ammonium that inhibits a large number of bacteria, including those of the genus Pseudomonas , other than Pseudomonas aeruginosa [ 10 ].

Sodium salts

Sodium salts are known for their inhibitory properties. The best known is sodium chloride, used to select halophilic bacteria that resist very high amounts of salts [ 49 ]. In addition, sodium deoxycholate has a strong solvent action on bacteria [ 50 ] ( Table 3 ).

Table 3

The Marine Agar 2216E culture medium is used to enumerate marine heterotrophic bacteria. It is composed of a high concentration of salt, which eliminates a large number of bacteria and preserves marine bacteria of interest [ 51 ].

Chemical substances

Chemical substances can be added to culture media to inhibit certain bacteria. These inhibiting substances include potassium tellurite and bile salts, which inhibit Gram-positive bacteria [ 10 , 39 , 52 ] or lithium chloride [ 10 , 39 ], which eliminates Gram-negative bacteria ( Table 4 ).

Table 4

Brayton et al. [ 53 ] have created a selective culture medium for Vibrio vulnificus , which is a pathogenic halophilic bacterium. This medium, VV agar, consists, among other things, of potassium tellurite as selective agent for inhibiting Enterobacteriaceae .

Dyes can be used as a colour indicator in a culture medium or as a selective agent against certain bacteria. Crystal violet is one of the most commonly used dyes to inhibit bacteria [ 37 , 54 ]. Malachite green and methylene blue are also used to inhibit Gram-positive and Gram-negative bacteria and Gram-positive bacteria, respectively [ 10 , 55 ] ( Table 5 ).

Table 5

A selective medium of Streptococcus pneumoniae has been developed, containing crystal violet. This dye is used to select streptococci and inhibit staphylococci as well as other Gram-positive bacteria [ 54 ].

Bacteriophages are specific viruses of bacteria that can infect and even destroy bacteria, in the case of lytic phages. In order to isolate Mycobacterium tuberculosis , the use of phage lysin decontaminates the sputum of other bacteria present in the pulmonary microbiota [ 56 ].

Sillankorva et al. [ 57 ] worked on permanent urinary tract infections due to Escherichia coli . In order to treat these infections, they tested different phages (T1, T4 and φX174-like phages) against E. coli . After 2 hours of treatment, phage T1 reduced the E. coli population by 45%, demonstrating the efficacy of this selective agent.

Disadvantages of gelling agents use

Liquid culture media versus solid culture media.

There are two main types of culture media, liquid and solid.

In liquid culture media, also called culture broths, nutrients are dissolved in water. The growth of bacteria in this type of medium can be demonstrated by the appearance of a turbidity in the medium, although this is not always the case. It is difficult to isolate a bacterium specifically in this type of medium. Indeed, the bacteria obtained from a sample inoculated into the culture broth are all mixed with each other. In addition, this type of culture medium does not allow the morphological characteristics of bacterial species to be identified [ 9 ].

However, liquid culture media facilitate access to nutrients for bacteria. These nutrients are all the more accessible as the culture media are incubated under agitation, allowing a renewal of nutrients for bacteria.

Solid culture media are obtained by adding a gelling agent, such as agar, to the culture broth. They make it possible to obtain isolated colonies of different bacterial species, which can be identified. The different morphological characteristics of the bacterium can be described from these cultures [ 9 , 58 ]. However, in solid culture media, access to nutrients for bacteria may be limited. Media with high gel content, such as agar, will form smaller colonies than low gel content media because nutrient flow and toxin removal are reduced [ 7 ].

In addition, it has been shown that agar, in excessive quantities, can inhibit the growth of certain bacteria, highlighting the need to find other gelling agents [ 9 ].

Different gelling agents

One of the first gelling agents used in culture media was gelatin. The problem with this gelling agent is that it melts at 37°C, which is the incubation temperature of most bacteria. Moreover, the presence of an enzyme in certain bacteria, gelatinase, causes the digestion of gelatin and therefore its degradation. Agar was then used in culture media. However, over-consumption of agar has led to a reduction in its source, red algae [ 59 ], which has increased costs. In addition, agarase, present in some bacteria, destroys agar, preventing the isolation of these bacteria [ 60 ]. In addition, agar can inhibit the growth of some anaerobic bacteria because inhibitory growth compounds can be produced from autoclaving phosphate with agar [ 61 ]. Finally, agar can cause inhibition of PCR of fungal DNA when extracted directly from the solid culture medium [ 62 ]. For all these reasons, new gelling agents have been sought. These gelling agents include κ-carrageenan, ι-carrageenan, sodium alginate, high-methoxyl and low-methoxyl pectins and gellan gum [ 60 , 63 ]. All these gelling agents have different properties and particular needs to gel ( Table 6 ).

Table 6

Gelling agents used in culture media [ 60 , 63 , 67 ]

Carrageenan gums

κ-carrageenan and ι-carrageenan are part of the carrageenan gums.

The first will form a firm gel with a rapid mass build-up when combined with potassium ions. It allows the growth of some bacteria. This gelling agent resists very alkaline pH values above 12.5, so can isolate very highly alkaliphilic bacteria [ 64 ]. It can be used to replace agar because many bacteria grow on κ-carrageenan-based media [ 65 ].

ι-carrageenan is rarely used because it gives elastic gels that make bacterial culture difficult [ 65 ].

Sodium alginate

This gelling agent is produced from brown seaweed extract and forms a flexible gel in the presence of calcium ions. However, this gelling agent does not provide a gel firm enough to grow bacteria [ 63 ].

High methoxyl and low methoxyl pectins

High-methoxyl pectins require sugar and high acidity to gel. Gel setting is slow and results in the formation of a ‘spreadable’ gel.

Low-methoxyl pectins form brittle gels in the presence of Ca 2+ [ 62 ].

Gellan gum is a polysaccharide produced by a bacterial genus, Sphingomonas spp. According to Tamaki et al. [ 66 ], 108 bacteria tested on media with gellan gum as gelling agent showed growth.

The use of these different gelling agents could allow the culture of new bacteria, which do not grow on the agar, because of the presence of an agarase for example or because the agar forms a network too dense to allow motility and optimal growth of certain bacteria [ 9 ].

Colony size

The amount of nutrients available in a culture medium will determine the size of bacterial colonies [ 58 ]. An overly firm culture medium, due to a high concentration of gelling agent, causes a decrease in the flow of nutrients and so a decrease in the access to these nutrients by bacteria [ 7 , 9 ]. On the other hand, in some culture media, the amount of nutrients available is too high and can be toxic for certain bacteria that require a poor culture medium to grow [ 68 ]. Microcolonies are colonies that are barely visible to the naked eye (between 100 and 300 μm in diameter). To obtain larger colonies, it is sometimes necessary to mimic the bacterium's natural environment by providing it with specific elements. This is the case, for example, for Phascolarctobacterium faecium and Phascolarctobacterium succinatutens , which form microcolonies. However, when the medium is supplemented with succinate, the colonies have a diameter ranging from 0.8 to 1.2 mm [ 69 , 70 ].

After stagnation in the development of new culture techniques, due to the rapid evolution of new microbiological methods such as metagenomics, bacterial culture is experiencing a new boom. In recent years, culturomics, with the use of new culture media and new culture conditions, has enabled the enrichment of the bacterial repertoire through the isolation of new bacterial species. This shows that, despite the abandonment of culture by a large number of microbiologists, culture media remain a fundamental tool for bacteriologists for the isolation of commensal but also pathogenic bacteria.

Studying the natural environment of bacteria that have remained uncultivated to date would be interesting because it would provide the essential elements for the bacteria to grow. Indeed, although there are many enriched culture media, each bacterium is unique and has specific requirements. The use of new gelling agents could also allow the isolation of new species for which agar was not suitable for their growth. Although many gelling agents have been tested, few are still used in commercial culture media and therefore in laboratories. Many developments in bacterial culture are therefore still to come, making it possible to enrich the bacterial repertoire and gain a better understanding of certain diseases.

In addition, intracellular bacteria such as Coxiella burnetii or Tropheryma whipplei require a host cell to survive and multiply. Some of these bacteria cause severe diseases and pose a diagnostic problem because of their fastidious growth or lack of growth on conventional media [ 71 ]. It would be interesting to develop culture media that allow faster and easier detection of these bacteria. In addition, as the microbiota plays an increasingly important role in human health [ 72 , 73 ], the development of probiotics is on the rise [ 74 ]. The use of targeted culture media to select certain bacteria with an important medical role therefore remains a priority.

Funding sources

This research is funded by the Agence Nationale de la Recherche as part of the Méditerranée Infection 10-IAHU-03 project.

Conflict of interest

No conflict of interest has been declared.

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Original research article, development and evaluation of culture media based on extracts of the cyanobacterium arthrospira platensis.

• 1 Department of Medicine and Life Sciences Universitat Pompeu Fabra, Barcelona, Spain
• 2 BioInspired Materials Company, Barcelona, Spain

Continuous advances in the fields of industrial biotechnology and pharmacy require the development of new formulations of culture media based on new nutrient sources. These new sources must be sustainable, high yielding, and non-animal-based, with minimal environmental impact. Thus, culture media prepared from cyanobacterial extracts can be an interesting alternative to the current formulations. In this study, we prepared various minimal formulations of culture media using the extracts of Arthrospira platensis , and analyzed the efficiency of these formulations, based on their effect on the production of biomass and molecules of industrial interest, using different types of bacteria. All media formulations prepared in this study showed better performance than conventional media, including those based on animal ingredients. Thus, based on their versatility and high-yielding capacity, we conclude that culture media prepared from cyanobacterial extracts are a good alternative to conventional media for meeting the current demands of the cosmetic and pharmaceutical industries.

Introduction

Technological advancements are continuously needed for a wide range of applications in biotechnological and pharmaceutical industries, such as the production of vaccines ( Plotkin et al., 2017 ), blood and blood components ( Haldar et al., 2019 ), cell lines for cell therapies ( Thakar et al., 2020 ), gene therapies ( Gonçalves and de Paiva, 2017 ; Papanikolaou and Bosio, 2021 ), and recombinant therapeutic proteins ( Dingermann, 2008 ; Qarawi et al., 2019 ). These advancements require new, high-yielding, and cost-effective formulations of culture media based on sources that are sustainable, have a zero or negative carbon footprint, and are preferably vegan, especially if used in the cosmetic industry ( Pathak and Martirosyan, 2012 ; Pathak and Singhal, 2013 ).

Soy is currently the most widely used nutrient in the production of animal compound-free media. Although soy shows excellent performance, the exponential increase in soybean production worldwide is generating a high negative environmental impact ( da Silva et al., 2021 ). Therefore, many efforts have been made in recent years to identify new sources of nutrients, especially those lacking components of animal origin, which could be used to prepare new culture media ( Arulanantham et al., 2012 ; Batista and Fernandes, 2015 ; Narh et al., 2018 ).

An alternative to animal component-based media, with great potential, are the extracts of cyanobacteria, such as Arthrospira spp. Cyanobacteria have long been known for their rich nutritional profile ( Schmidt and Jónasdóttir, 1997 ; Bahlol, 2014 ), and their commercial use as a food supplement for human and animal health is becoming more widespread. Not only can these photosynthetic microorganisms be cultivated on a large scale in a small area at low cost, but they also absorb atmospheric CO 2 during growth, thus having a positive environmental impact. Despite these advantages, there are currently no commercially available culture media prepared from the hydrolyzed extracts of cyanobacteria. Moreover, little research has been done to explore the potential of cyanobacteria as a raw material for the development of new culture media ( Jeong et al., 2021 ).

In this study, we explored the performance of cyanobacterial extract (CE)-based formulations in terms of their (i) versatility for the growth of diverse organisms; (ii) biomass production yield; (iii) protein expression; and (iv) production of molecules of industrial interest, with a primary focus on the expression of recombinant proteins in Escherichia coli and the production of bacterial cellulose, one of the most interesting biomaterials owing to its unique properties ( Betlej et al., 2021 ) that can be applied in multiple industrial and biomedical applications ( Chang and Chen, 2016 ; Picheth et al., 2017 ). To this end, the set of strains analyzed include (i) bacteria from very different environments and living in different atmospheric conditions, i.e., aerobic and anaerobic strains, (ii) pathogenic and non-pathogenic strains, and (iii) strains of industrial interest in various fields, from protein production to treatment of plant diseases in agriculture.

The minimal media analyzed in this study were composed of either the CE alone or a combination of CE and yeast extract (YE).

Materials and methods

Media composition.

All culture media analyzed in the study contained, as the main ingredient, the hydrolyzed extract of Arthrospira platensis (Ficogenic®), and were supplied as a concentrated liquid by BioInspired Materials Company (BIOM, Barcelona, Spain). Composition of A. platensis extract was analyzed in collaboration with the Eurofins Company. Results are shown in Supplementary Table S1 . The composition analysis showed significant amounts of amino acids, sugars, and carbohydrates indicating, a priori , a composition rich enough to cover the nutritional needs of diverse types of microorganisms.

Different formulations ( Table 1 ) were prepared by directly diluting the CE in distilled water with or without 0.5% (w/v) YE. Then, the formulations were sterilized followed by autoclaving at 121°C for 20 min.

Table 1 . Composition of minimal media prepared in this study.

The performance of culture media was evaluated by comparing the growth of different microorganisms in a test culture medium and on a reference culture medium, which was selected based on the specifications of the American Type Culture Collection (ATCC). The different microorganisms, reference media, and culture temperatures analyzed in this study are listed in Table 2 . It should be noted that these bacteria originate from very different environments and have different nutritional requirements.

Table 2 . List of microorganisms and corresponding reference culture media (according to ATCC) analyzed in this study.

Some of the reference media were prepared in the laboratory ( Supplementary material ) using commercially available ingredients including yeast extract (Sigma-Aldrich Y1625), glucose (Sigma-Aldrich G8270), tryptone (Sigma-Aldrich T9410), beef extract (Sigma-Aldrich B4888), sodium acetate (Sigma-Aldrich S2889), CaCO 3 (Sigma-Aldrich 239216), peptone (VWR J636), mannitol (Labkem MANL-00A-500), Tryptic Soy Broth (Sigma-Aldrich 22092), and defibrinated sheep blood (Thermo Scientific SR0051C).

Other media used in this study were purchased from commercial manufacturers: SOC Medium (Thermo Fisher 15544034) and 2YT (Sigma-Aldrich Y2377).

Bacterial cultures

All cultures were prepared by inoculating a single colony into the corresponding medium, and maintained at the proper temperature ( Table 2 ) with orbital shaking at 200 rpm for 20 h.

For the preparation of cultures from lyophilized E. coli , 1 mg of lyophilized powder was resuspended in 50 μl of PBS. Next, 180 μl of each culture medium was loaded into the wells of a 96-well plate. Finally, each well was inoculated with 2 μl of the E. coli cell suspension in PBS. Time course measurements were done with Synergy HXT-Multi-Mode Reader (BioTek Instruments, United States) at 37°C with continuous orbital shaking at 200 rpm for 20 h.

The AnaeroGen™ 2.5 l system (Thermo Scientific) was used to grow microorganisms in an anaerobic atmosphere.

Recombinant protein expression

To evaluate the expression of recombinant proteins, E. coli DH5α strain was transformed with the plasmid pSB1C3, which contained the Green Fluorescent Protein ( GFP ) gene under the control of a constitutive promoter (see Supplementary Table S2 for details).

Optical density and fluorescence measurements

To measure the optical density (OD) and fluorescence of different cultures, a 4 ml volume of each culture medium was prepared. After 20 h of culture at the appropriate temperature with shaking, 1 ml of each culture was centrifuged for 2 min at 13,000× g . The supernatant was subsequently removed, and the pellet was resuspended in phosphate-buffered saline (PBS). Finally, 200 μl of each culture was loaded onto a 96-well plate. The OD of each culture was measured at a wavelength of 600 nm. Fluorescence measurements were recorded at emission and excitation wavelengths of 509 ± 9 nm and 475 ± 9 nm, respectively, with Synergy HXT-Multi-Mode Reader (BioTek Instruments, United States). Experimental data were collected with the Gen5 software package and analyzed with Microsoft Excel 2019. The fluorescence of each culture was calculated using the following equation:

where GFP 0 and OD 0 represent the fluorescence and OD values of PBS (blank), respectively.

DNA transformation protocol

For DNA transformation, 120 μl of a culture of competent E. coli DH5α was mixed with 0.2 μl of DNA and maintained on ice for 20 min. To induce heat shock, each cell culture was exposed to a high temperature (45°C) for 45 s. Subsequently, the cells were incubated on ice for 10 min. Then, 20 μl of the transformed cells were transferred to Eppendorf tubes containing 480 μl of the different media, and cultured for 1 h at 37°C with constant shaking at 350 rpm. Finally, the contents of each tube were spread on a Petri dish containing LB-agar medium and stored at 37°C overnight.

Escherichia coli lyophilization

A culture of E. coli was prepared in 10 ml of LB medium overnight at 37°C. Subsequently, the culture was centrifuged and the supernatant was removed. The pellet was resuspended in 10 ml of 10% (w/v) sucrose solution. The suspension was frozen with liquid nitrogen and then placed in a lyophilizer (Telstar LyoAlfa 15) for 48 h.

Statistical analysis

Results shown in figures are the mean of three independent experiments. Error bars are the standard deviation of the three independent experiments. The statistical significance of the results obtained using the different CE-based media analyzed vs. the results obtained using the reference medium was determined by the value of p in the Student’s t -test. The range of the value of p is shown in each figure according to * p  < 0.05, ** p  < 0.01, *** p  < 0.001, and – for no statistical significance.

Efficiency of biomass production using CE-based media

One of the important aspects of many biotechnological applications at the industrial level is to achieve high densities of microorganisms in bioreactors. For example, the production of biopesticides ( Ernandes et al., 2013 ; Morales-Borrell et al., 2020 ), biofertilizers ( Mukhtar, 2018 ), and lactic ferments ( Coelho et al., 2011 ), among other products, requires optimized media for producing large amounts of biomass. As a result, the industry continues to seek new sources of nutrients. To reach the objective of increasing biomass production, formulations with specific compositions for each type of microorganism are generally developed. These media formulations are based on the combination of different carbon and nitrogen sources of both animal and vegetable origin. The first objective of this study was to evaluate the efficiency of CE-based media as a general nutritional basis for biomass production, regardless of the particular characteristics of each type of microorganism. This represents a significant simplification in the formulation of the new media, based principally on a single source of nutrients, which, in turn, is associated with simplifying production processes and reducing production costs.

To evaluate the efficiency of CE-based media, we performed multiple growth assays using all formulations ( Table 1 ) with different types of bacteria ( Table 2 ). The culture conditions, in terms of oxygen level (aerobic or anaerobic) and temperature, varied with the type of microorganism. The growth of each microorganism was evaluated on the test formulation and the reference medium ( Table 2 ) under the same conditions. The results of cell growth assays, measured in terms of OD, are shown in Figure 1 . Figures 1A – F show the optical density measured in different types of aerobic bacterial cultures using the CE-based media described in Table 1 , whereas Figures 1G , H show the optical density in two different types of anaerobic bacterial cultures, for each CE-based media.

Figure 1 . Optical density of bacterial cultures in different CE-based media. (A–F) Aerobic cultures. (G,H) Anaerobic cultures. Data are the average of three independent experiments. Red bars correspond to the reference media. Error bars are the standard deviation of three independent experiments. p -values * p  < 0.05, ** p  < 0.01, *** p  < 0.001, and – p  ≥ 0.05.

In general, the experimental results show a direct relationship between CE concentration and biomass production in all strains analyzed, showing higher OD values on formulations containing >10% CE than on the reference media, indicating a higher rate of cell growth. It should be noted that media composed of both CE and YE performed better than media composed of CE alone. This trend was observed with all microorganisms studied, regardless of their intrinsic characteristics.

However, in some strains, this ratio is not satisfied at higher CE concentrations, i.e., 30%. A possible cause could be elevated osmotic stress associated with these media with elevated concentrations. This would be consistent with previous results. For example, high salinity has been reported to negatively impact strains like Bacillus thuringiensis ( Jiang et al., 2006 ) or C. Necator ( Passanha et al., 2014 ).

Despite this negative effect at higher CE concentrations in some strains, the CE-based media contained no animal-derived components; nonetheless, the levels of biomass production obtained using CE-based media were better than those obtained using reference media such as nutrient broth (for Bacillus subtilis and B. thuringiensis ; which contains beef extract), brain heart infusion broth (for Cutibacterium acnes ), and Trypticase soy broth with 5% defibrinated sheep blood (for Bacteroides fragilis ). This is a remarkable result because some of these strains are characterized by being difficult to grow, indicating that CE-based media are a good alternative to animal fluid-based media.

Evaluation of CE-based culture media as an alternative to enriched media

Given the positive effects of CE-based media on cell growth, we compared the performance of these media with that of two enriched media (2YT and SOC), which are commonly used for cell recovery post-transformation.

In both cases, the fragility of the cells can affect their survival rate. In these circumstances, the media composition plays a key role in the rate of cell growth. This is particularly relevant in the case of massive use of lyophilized microorganisms, for instance as biofertilizers in agriculture, where rehydration of lyophilized cells before their application improves functional properties ( Arellano-Ayala et al., 2021 ).

In order to evaluate the efficiency of CE-based media in DNA transformation, E. coli strain was transformed with a plasmid constitutively expressing GFP. Specifically, the pSB1C3 plasmid containing the GFP gene under the control of the constitutive J23100 promoter was constructed and transformed into E.coli (see Supplementary material for details).

The number of colony-forming units (CFUs) was counted to determine the effect of the culture medium on the transformation efficiency. Figure 2A shows the CFUs of cultures in CE-media (CFU CE medium ) relative to those in SOC medium (CFU SOC ), i.e., CFU CE medium /CFU SOC . Similarly, Figure 2B shows the CFUs relative to those in 2YT medium, i.e., CFU CE medium /CFU 2YT . As figures show, the transformation efficiencies obtained using P3 and M2 media were 20% higher than those obtained using SOC and 40% higher than those obtained using 2YT.

Figure 2 . DNA transformation efficiency of bacterial grown in different CE-based media after heat shock. (A) The CFUs of cultures in CE-media are expressed relative to those in SOC medium. (B) The CFUs of cultures in CE-media are expressed relative to those in 2YT medium. Data are the average of three independent experiments. Error bars are the standard deviation of three independent experiments. p -values * p  < 0.05, ** p  < 0.01, *** p  < 0.001, and – p  ≥ 0.05.

Finally, we analyzed the growth of lyophilized E. coli in CE-based media that produced a higher yield in cell growth assays along with 2YT and SOC as reference media. Figure 3A shows the growth curves of lyophilized E. coli -derived cultures in P1–P5 media compared with the growth dynamics of cultures in SOC and 2YT. Similarly, Figure 3B compares the growth dynamics of cultures in M1-M5 with those in SOC and 2YT. Although the 2YT medium showed the best results, the performance of M3 medium was similar to that of 2YT, indicating that M2 is a good alternative to 2YT. On the other hand, media containing >10% CE exhibit better performance than SOC cultures.

Figure 3 . Growth curves of lyophilized Escherichia coli -derived cultures. (A) Comparison of the growth dynamics of cultures in P1–P5 media and those in SOC and 2YT media. (B) Comparison of the growth dynamics of cultures in M1–M5 media and those in SOC and 2YT media. Error bars are the standard deviation of three independent experiments.

Experimental results show that combining CE with YE is significantly more effective than CE-only formulations. However, it is worth mentioning that increasing concentrations of CE does not imply better performance neither in terms of transformation efficiency nor in the growth of lyophilized E. coli -derived cultures, similar to the previous observed effect on growth of some of the strains analyzed.

Efficiency of the production of molecules of interest using CE-based culture media

One of the areas where the search for new sources of nutrients is more intense is the industry dedicated to producing biomolecules and biomaterials. Here, the formulation of new sustainable, low-cost, and high-yielding culture media is challenging.

To evaluate the potential of CE-based media as a substrate for the industrial-scale production of biomolecules, two case studies were considered: the production of recombinant proteins in E. coli and production of bacterial cellulose using Gluconacetobacter xylinus (strain ATCC 23767) and Komagataeibacter sucrofermentans (strain ATCC 700178).

Constitutively expressed GFP was used as the recombinant protein (see Supplementary material ). A preculture of E. coli was prepared in LB medium and maintained at 37°C overnight on a shaker at 300 rpm. Subsequently, 4 ml of each culture medium ( Table 1 ) and LB (reference medium) was prepared. Finally, 2 μl of the preculture was used to inoculate these media, and the inoculated media were incubated for 20 h at 37°C and 300 rpm.

Figure 4A shows the OD and Figure 4B shows GFP/OD data. Compared with LB, the P2, P3, M2, and M3 media showed higher protein yield. As previously observed, the media with the highest CE concentrations (P1 and M1) showed lower efficiency, which was comparable with that obtained using LB. However, a reduction in CE concentration led to a significant increase in both cell number (OD value) and GFP signal per cell.

Figure 4 . Recombinant GFP expression levels in Escherichia coli . (A) Optical densities of E. coli cultures. (B) GFP fluorescence normalized to optical density. Red bars correspond to the reference media. Data are the average of three independent experiments. Error bars are the standard deviation of three independent experiments. p -values * p  < 0.05, ** p  < 0.01, *** p  < 0.001, and – p  ≥ 0.05.

The second case study focused on the production of bacterial cellulose, which is a polymer of great interest. Intensive research is currently being conducted to develop new media that could increase the production of bacterial cellulose ( Gorgieva and Trček, 2019 ; de Fernandes et al., 2020 ; Zhong, 2020 ; Wahid et al., 2021 ). In this study, precultures of both G. xylinus and K. sucrofermentans were prepared overnight at 27°C using mannitol broth and YGC medium, respectively (see Supplementary material for media composition). Subsequently, Petri dishes containing 20 ml of media ( Table 1 ), in addition to control plates containing mannitol broth or YGC medium, were prepared and inoculated with 2 μl of the corresponding preculture. It should be noted that CE-based media were supplemented with 5% (w/v) glucose. The plates were incubated at 27°C for 14 days in static culture.

The bacterial cellulose membranes produced were collected, immersed in 0.1 M NaOH solution, and heated to 90°C with string for 2 h to remove cellular debris ( Hashim et al., 2021 ). Then, the membranes were washed several times with distilled water to remove excess NaOH until the pH decreased to 6.5. The purified membranes were lyophilized for 2 days and their dry weight was determined. Figure 5A shows the production of BC (in g/L) in K. sucrofermentans cultures, whereas Figure 5B shows the results obtained in G. Xylinus cultures. The results showed that bacterial cellulose membranes were not formed in culture media containing high CE concentrations and lacking YE. The mechanism that inhibits the formation of bacterial cellulose remains unclear but could be related to media osmolality. However, a significantly higher amount of bacterial cellulose was produced with both strains in media containing low CE concentrations compared with reference media, making the CE-based media especially valuable for bacterial cellulose production.

Figure 5 . Dry weights of bacterial cellulose (BC; g/L) from cultures grown in different CE-based media. (A) BC produced by K. sucrofermentans . (B) BC produced by G. xylinus . Red bars correspond to the reference media. Data are the average of three independent experiments. Error bars are the standard deviation of three independent experiments. p -values * p  < 0.05, ** p  < 0.01, and – p  ≥ 0.05.

Many efforts are currently underway to find new sources of nutrition for microbiology applications, with a particular focus on finding alternatives that do not use animal-derived components. The industry currently demands new media formulations that offer high yields at low cost, can be produced in a sustainable manner, and thus have a minimal environmental impact. Compared with other nutritional sources, cyanobacteria contain the highest levels of proteins, amino acids, minerals, pigments, vitamins, and polysaccharides ( Panjiar et al., 2017 ). It is worth mentioning that cyanobacteria can be produced in an ecological and sustainable manner and at low cost just using industrial waste products and atmospheric CO 2 ( Zhu et al., 2020 ; Lim et al., 2021 ). Nonetheless, little research has been conducted in the field of microbiology on the use of cyanobacteria as a nutritional source for the production of culture media.

This study analyzed the efficiency of new formulations of culture media based on the extract of Arthrospira platensis as the main ingredient.

First, these media were evaluated for biomass production using both aerobic and anaerobic bacteria, and were compared with different reference media containing ingredients of animal origin, such as beef extract, brain heart infusion, or blood. Increasing biomass production is one of the most important challenges for multiple industries, such as probiotic or lactic ferments producers among others.

All CE-based media analyzed showed better results, in terms of cell growth, than the corresponding reference media. Importantly, best results were also obtained with microorganisms requiring ingredients of animal origin in the standard media. These results indicate that CE-based media are a good alternative to animal component-based media because of their high performances and cost-effective production and have higher consumer acceptance, especially in cosmetic and pharmaceutical industries, where new animal ingredient-free and ecologically produced media are preferred.

Related with the positive effects of CE-based media in cell growth, two interesting applications have been explored, namely the effects of CE-based in the DNA transformation efficiency and the in the culturing of lyophilized cells.

Increasing DNA transformation efficiency is appealing for multiple industrial applications. For instance, recombinant DNA technology plays a vital role in improving health conditions by developing new vaccines and pharmaceuticals or in the production of diverse industrial products ( Adrio and Demain, 2010 ).

Regarding the use of lyophilized microorganisms, it should be noted that lyophilization is the optimal method for preserving microorganisms and their use is of great interest in sectors such as agriculture, where the use of lyophilized microorganisms for the treatment of plant pathologies, to promote plant growth and enhance biotic and abiotic stress resistance is increasingly widespread ( Ma et al., 2021 ). It has been reported that rehydration of lyophilized cells before their application improves functional properties ( Arellano-Ayala et al., 2021 ).

For both cases, DNA transformation and rehydration of lyophilized cells, enriched media, such as SOC or 2YT, are required. This study demonstrates that CE-based media can be used for both purposes, improving the efficiency of DNA transformation and achieving similar or better performance in the culturing of lyophilized cells when compared with SOC and 2YT. Hence, CE-based media could represent an optimal alternative to the standard media, for sustainable, ecological, and vegan production processes.

Finally, the CE-based media showed great potential for the production of biomolecules of industrial interest, especially recombinant proteins in E. coli and bacterial cellulose production in G. xylinus and K. sucrofermentans . Increasing the production of proteins and biomaterials such as BC is a challenge for industry. Many efforts have been devoted to design and optimize culture media combining high performance with cost-effectiveness. In both cases, CE-based media have shown better performance compared to standard media. The uses of CE-based media may represent a significant advance toward an improved industrial production of recombinant proteins and biomaterials.

However, it is necessary to dedicate more efforts to the design and optimization of new formulations of CE-based media. It has been observed that the increase in the concentration of CE in the formulations of the culture media is not always directly associated with an increase in their performance. Actually, in some cases, increasing CE concentrations beyond a critical level has a negative effect. Although the reason for this behavior is not clear, these results suggest that the osmotic stress produced by high concentrations of CE can affect the media efficiency, pointing out that it is necessary to optimize the formulation of the medium for each type of bacteria.

In summary, this study shows that CE-based media can serve as efficient sources of nutrition for a wide range of bacteria originating from different environments, and can be used in various types of applications such as the production of biomass and molecules of interest. These results, together with the low cost of production of cyanobacteria using industrial waste products and atmospheric CO 2 , make cyanobacteria a very attractive alternative for the formulation of new animal compound-free media.

Despite the great potential of CE-based media, their applications have not been explored thoroughly. Future work should focus on exploring the potential use of CE-based media in other cellular strains, such as mammalian cell growth.

Data availability statement

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

Author contributions

JM conceived the experiments and wrote the manuscript. EK and JM performed the experiments. All authors contributed to the article and approved the submitted version.

Funding for this study and for the open access charge was in the form of grants from the Industrial Doctorate Program funded by the Generalitat de Catalunya. This work was supported by “Unidad de Excelencia María de Maeztu,” funded by the MCIN and the AEI (DOI: 10.13039/501100011033). Ref: CEX2018-000792-M. Ficogenic® development, production and characterization was supported by ACCIO, Generalitat de Catalunya.

Acknowledgments

We thank Ramón Farré-Escofet, Inés Arteaga and Dr. Carlos Rodriguez-Caso for fruitful conversations.

Conflict of interest

The cyanobacteria extracts used in this study (Ficogenic®) were commercial products developed by the Biom Company, a spin-off of Univesitat Pompeu Fabra. This study was developed as part of an Industrial Doctorate Program under an agreement between the Universitat Pompeu Fabra and the Biom Company.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher’s note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

Supplementary material

The Supplementary material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fmicb.2022.972200/full#supplementary-material

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Keywords: cyanobacterium extracts, microbiology, Arthrospira platensis , culture media, animal and vegetal component free media, bacterial cellulose, not animal-derived culture medium, industrial biomolecules

Citation: Kheirabadi E and Macia J (2022) Development and evaluation of culture media based on extracts of the cyanobacterium Arthrospira platensis . Front. Microbiol . 13:972200. doi: 10.3389/fmicb.2022.972200

Received: 17 June 2022; Accepted: 13 July 2022; Published: 09 August 2022.

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Copyright © 2022 Kheirabadi and Macia. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) . The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: Javier Macia, [email protected]

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Use of products of vegetable origin and waste from hortofruticulture for alternative culture media

Conventional culture media are expensive owing to their constituents. Thus, several studies have sought to develop and evaluate the efficacy of alternative, low-cost culture media, in most cases, using natural and easily accessible raw materials. The present study is a literature review, observing various formulations of culture media based on products of plant origin for the growth of microorganisms and production of microbial compounds of industrial interest. In most formulations, vegetable substrates, such as soy, certain beans, corn, and rice, were used in addition to hortofruticultural products. Compared to conventional media, the alternative culture media often present satisfactory results in terms of microbial growth efficiency and production cost.

Keywords: alternative culture media; low cost; formulations; food waste

1 Introduction

Ways of reusing food waste have been constantly developed and improved, as food waste reaches alarming levels today ( Ramírez et al., 2020 Ramírez, J. A., Castañón-Rodríguez, J. F., & Uresti-Marín, R. M. (2020). An exploratory study of possible food waste risks in supermarket fruit and vegetable sections. Food Science and Technology. In press. http://dx.doi.org/10.1590/fst.27320. http://dx.doi.org/10.1590/fst.27320... ). Thus, the development of methodologies for the use of different types of food waste, whether of animal or vegetable origin, has aroused the interest of the scientific community, in order to obtain new products or compounds of interest, or to optimize processes ( Navarro-Peraza et al., 2020 Navarro-Peraza, R. S., Osuna-Ruiz, I., Lugo-Sánchez, M. E., Pacheco-Aguilar, R., Ramírez-Suárez, J. C., Burgos-Hernández, A., Martínez-Montaño, E., & Salazar-Leyva, J. A. (2020). Structural and biological properties of protein hydrolysates from seafood by-products: a review focused on fishery effluents. Food Science and Technology, 40(1, Suppl. 1), 1-5. http://dx.doi.org/10.1590/fst.24719. http://dx.doi.org/10.1590/fst.24719... ; Leira et al., 2019 Leira, M. H., Nascimento, A. F., Alves, F. R., Orfao, L., Lacerda, Y. G., Botelho, H. A., Reghim, L., & Lago, A. A. (2019). Characterization of different techniques for obtaining minced fish from tilapia waste. Food Science and Technology, 39(1, Suppl. 1), 63-67. http://dx.doi.org/10.1590/fst.37517. http://dx.doi.org/10.1590/fst.37517... ; Costa et al., 2020 Costa, R. S., Santos, O. V., Lannes, S. C. S., Casazza, A. A., Aliakbarian, B., Perego, P., Ribeiro-Costa, R. M., Converti, A., & Silva, J. O. C. Jr. (2020). Bioactive compounds and value-added applications of cupuassu (Theobroma grandiflorum Schum.) agroindustrial by-product. Food Science and Technology, 40(2), 401-407. http://dx.doi.org/10.1590/fst.01119. http://dx.doi.org/10.1590/fst.01119... ).

Agro-industrial waste has great diversity and has been shown to have potential for application in different areas, such as use as a source of fibers, polyphenols and bioactive compounds in general ( Costa et al., 2020 Costa, R. S., Santos, O. V., Lannes, S. C. S., Casazza, A. A., Aliakbarian, B., Perego, P., Ribeiro-Costa, R. M., Converti, A., & Silva, J. O. C. Jr. (2020). Bioactive compounds and value-added applications of cupuassu (Theobroma grandiflorum Schum.) agroindustrial by-product. Food Science and Technology, 40(2), 401-407. http://dx.doi.org/10.1590/fst.01119. http://dx.doi.org/10.1590/fst.01119... ; Tagliani et al., 2019 Tagliani, C., Perez, C., Curutchet, A., Arcia, P., & Cozzano, S. (2019). Blueberry pomace, valorization of an industry by-product source of fibre with antioxidant capacity. Food Science and Technology, 39(3), 644-651. http://dx.doi.org/10.1590/fst.00318. http://dx.doi.org/10.1590/fst.00318... ), organization and management of fruit and vegetable residues for human and animal consumption ( Ramírez et al., 2020 Ramírez, J. A., Castañón-Rodríguez, J. F., & Uresti-Marín, R. M. (2020). An exploratory study of possible food waste risks in supermarket fruit and vegetable sections. Food Science and Technology. In press. http://dx.doi.org/10.1590/fst.27320. http://dx.doi.org/10.1590/fst.27320... ) and application in the development of alternative culture media ( Cruz et al., 2020 Cruz, C. H. S., Santos, J. B., Santos, F. P., Silva, G. M. M., Cruz, E. F. N., Ramos, G. L. P. A., & Nascimento, J. S. (2020). Texturized soy protein as an alternative low-cost media for bacteria cultivation. Bacterial Empire, 3(4), 74-76. http://dx.doi.org/10.36547/be.2020.3.4.74-76. http://dx.doi.org/10.36547/be.2020.3.4.7... ).

Culture media provides microorganisms with the necessary nutrients for their growth. Numerous raw materials exist for preparing these media that can be used for microbial growth or for other purposes, such as selective, differential media, and media used to stimulate microbial compound production ( Rouf et al., 2017 Rouf, A., Kanojia, V., Naik, H. R., Naseer, B., & Qadri, T. (2017). An overview of microbial cell culture. Journal of Pharmacognosy and Phytochemistry, 6(6), 1923-1928. Retrieved from https://www.phytojournal.com/archives/?year=2017&vol=6&issue=6&ArticleId=2312 https://www.phytojournal.com/archives/?y... ).

In developing countries, the high cost of culture media hampers practical microbiology classes and scientific research in institutions with insufficient financial resources ( Uthayasooriyan et al., 2016 Uthayasooriyan, M., Pathmanathan, S., Ravimannan, N., & Sathyaruban, S. (2016). Formulation of alternative culture media for bacterial and fungal growth. Der Pharmacia Lettre, 8(1), 431-436. Retrieved from https://www.scholarsresearchlibrary.com/articles/formulation-of-alternative-culture-media-for-bacterial-and-fungal-growth.pdf https://www.scholarsresearchlibrary.com/... ; Jadhav et al., 2018 Jadhav, P., Sonne, M., Kadam, A., Patil, S., Dahigaonkar, K., & Oberoi, J. K. (2018). Formulation of cost effective alternative bacterial culture media using fruit and vegetables waste. International Journal of Current Research and Review, 10(2), 6. http://dx.doi.org/10.7324/IJCRR.2018.1022. https://doi.org/ http://dx.doi.org/10.73... ; Cruz et al., 2020 Cruz, C. H. S., Santos, J. B., Santos, F. P., Silva, G. M. M., Cruz, E. F. N., Ramos, G. L. P. A., & Nascimento, J. S. (2020). Texturized soy protein as an alternative low-cost media for bacteria cultivation. Bacterial Empire, 3(4), 74-76. http://dx.doi.org/10.36547/be.2020.3.4.74-76. http://dx.doi.org/10.36547/be.2020.3.4.7... ). Thus, some studies have noted that vegetable-based formulations maybe advantageous as alternative (non-commercial) culture media, since these substrates provide several nutrients, including proteins, essential for the growth of microorganisms ( Ravimannan & Pathmanathan, 2016 Ravimannan, S. P., & Pathmanathan, S. (2016). Soy flour as alternative culture media for yeasts. Global Journal of Science Frontier Research, 16(3), 75-78. Retrieved from https://globaljournals.org/item/6617-soy-flour-as-alternative-culture-media-for-yeasts https://globaljournals.org/item/6617-soy... ). These methods are in development, aiming at improved sustainability using waste products or parts of food plants that are rarely used in human food, such as stems and vegetable peels.

In this review, we present recent studies involving alternative culture media that are formulated with products of plant origin. Thus, the objective is to provide as scientific basis for, and encourage the development and use of, these culture media in educational and research institutions with financial limitations for the acquisition of conventional culture media.

2 General view of the use of alternative culture media

Microorganisms depend on favorable conditions for their growth, such as optimal temperature and adequate nutrients. Regarding the latter, the components of some vegetables can provide the necessary microbial nutrition upon their use in culture media. Through assessing scientific publications, alternative culture media could be divided according to their purpose: media aimed at microbial growth and media for production of microbial compounds ( Table 1 ).

3 Alternative culture media for microbial growth

In addition to high nutritional value, soy plays an important role in the economy of Brazil as a major worldwide export ( Cattelan & Dall’Agnol, 2018 Cattelan, A. J., & Dall’Agnol, A. (2018). The rapid soybean growth in Brazil. Oilseeds & Fats Crops and Lipids, 25(1), D102. https://doi.org/10.1051/ocl/2017058. https://doi.org/10.1051/ocl/2017058... ). Soy is among the most versatile foods regarding its application in culture media. Several commercial media use soy as the main source of nutrients; therefore, its use in alternative culture media has been studied extensively.

Our group published a study in which textured soy protein (PST), easily acquired in markets, was used in concentrations from 0.5% to 10% in the preparation of alternative culture media. Thirty-eight bacteria, including major pathogens and food-related spoilage bacteria, such as Bacillus cereus, Micrococcus luteus, Escherichia coli, Hafnia alvei, and Serratia marcescens , were inoculated into media containing different concentrations of PST. A concentration of 7.5% allowed the growth of all the tested bacterial species. In addition to being effective for microbial growth, the medium’s production cost was 86% less than tryptone soy broth and 68% less than tryptone soy agar. The work demonstrated the viability of an easily formulated, low cost, and highly efficient culture medium ( Cruz et al., 2020 Cruz, C. H. S., Santos, J. B., Santos, F. P., Silva, G. M. M., Cruz, E. F. N., Ramos, G. L. P. A., & Nascimento, J. S. (2020). Texturized soy protein as an alternative low-cost media for bacteria cultivation. Bacterial Empire, 3(4), 74-76. http://dx.doi.org/10.36547/be.2020.3.4.74-76. http://dx.doi.org/10.36547/be.2020.3.4.7... ).

In a study carried out in Sri Lanka aiming to evaluate the growth of yeast strains ( Saccharomyces sp. and Schizosaccharomyces sp.), a culture medium based on soy flour was developed. The authors reported that the alternative soy flour medium was more efficient in growing yeast than the conventional culture medium. An additional advantage is the ease of soy flour acquisition by milling soy, which is approximately 50 times cheaper than the commercial medium containing peptone and yeast extract ( Ravimannan & Pathmanathan, 2016 Ravimannan, S. P., & Pathmanathan, S. (2016). Soy flour as alternative culture media for yeasts. Global Journal of Science Frontier Research, 16(3), 75-78. Retrieved from https://globaljournals.org/item/6617-soy-flour-as-alternative-culture-media-for-yeasts https://globaljournals.org/item/6617-soy... ).

Caldeirão et al. (2015) Caldeirão, L., Bosso, A., Tomal, A. A. B., Busanello, M., & Spinosa, W. A. (2015). Avaliação do desenvolvimento de bactérias lácticas em melaço de soja. Blucher Biochemistry Proceedings, 1(2), 369. http://dx.doi.org/10.5151/biochem-vsimbbtec-22158. http://dx.doi.org/10.5151/biochem-vsimbb... evaluated the growth of lactic acid bacteria in a culture medium based on soy molasses. The molasses was obtained from defatted soy flour and washed with a hydroalcoholic solution. Thereafter, the solvent was evaporated, and the concentrated solutes formed the molasses. This Brazilian study showed that all the lactic acid bacteria tested could grow in the soy molasses medium; however, the Bifidobacterium lactis Bb-12 and Lactobacillus helveticus LH-13 strains grew best in this medium, presenting counts greater than 10 8 CFU/mL.

Natural and processed soy flour, rice, chickpeas, and corn were also used individually as a basis for alternative media in a Sri Lankan study. The authors tested different microorganisms, comparing their growth in both formulated and commercial media, such as nutrient agar for bacteria and potato dextrose agar (PDA) for fungi. The formulated media allowed the tested microorganisms to grow, advocating the use of cheap and easily acquired raw materials, such as rice, chickpeas, corn, and soy, in formulating alternative media for bacteriological and mycological studies ( Uthayasooriyan et al., 2016 Uthayasooriyan, M., Pathmanathan, S., Ravimannan, N., & Sathyaruban, S. (2016). Formulation of alternative culture media for bacterial and fungal growth. Der Pharmacia Lettre, 8(1), 431-436. Retrieved from https://www.scholarsresearchlibrary.com/articles/formulation-of-alternative-culture-media-for-bacterial-and-fungal-growth.pdf https://www.scholarsresearchlibrary.com/... ).

In addition to soy, other vegetables have been used in culture media compositions. In a study conducted in Iraq, natural vegetable protein from various grains (rice, lentils, peas, chickpeas, soybeans, cowpeas, and mung beans) was used to formulate alternative media. The author reports that, with the exception of the rice-based medium, all other media proved effective in growing the tested microorganisms, which included bacteria and fungi commonly associated with food spoilage or diseases ( Staphylococcus aureus , E. coli , B. cereus , Pseudomonas aeruginosa , Penicillium sp., and Aspergillus sp.). Given the satisfactory results, the author stated that these alternative media could easily replace conventional culture media ( Shareef, 2019 Shareef, S. A. (2019). Formulation of alternative culture media from natural plant protein sources for cultvation of different bacteria and fungi. Zanco Journal of Pure and Applied Sciences, 31(4), 61-69. http://dx.doi.org/10.21271/zjpas.31.4.7. http://dx.doi.org/10.21271/zjpas.31.4.7... ). In the Philippines, Gabunia et al. (2019) Gabunia, K., Deslate, H. M., & Garcia, J. (2019). Effectiveness of corn husk extract as an alternative culture media for the growth of Escherichia coli and Staphylococcus aureus. Biology and Life Sciences, 39(2), 4. Retrieved from https://ijrp.org/paper-detail/758 https://ijrp.org/paper-detail/758... evaluated corn extract as an alternative growth medium for S. aureus and E. coli . The results revealed that the alternative medium presented the same results as the commercial nutrient agar.

Andrade (2017) Andrade, C. P. (2017). Meios de cultura alternativos para a produção de biomassa de Pleurotus eryngii (Trabalho de conclusão de curso). Universidade do Estado do Amazonas, Manaus. described the formulation of alternative culture media for biomass production from the edible mushroom Pleurotuseryngii . The media were developed by submerged fermentation using an infusion of cooked Amazonian vegetable substrates, such as manioc, purple-skinned sweet potato, purple yam, and white yam, at a concentration of 20% (v/v), with the addition of 2% glucose. All preparations resulted in satisfactory biomass production, with emphasis on those based on purple-skinned sweet potato and white yam.

Vegetable stems and fruit peels are often discarded or used in compost; however, these organs have a high nutritional value, since fruits and vegetables have a considerable amount of starch and proteins, and their use could considerably reduce the cost of producing culture media ( Jadhav et al., 2018 Jadhav, P., Sonne, M., Kadam, A., Patil, S., Dahigaonkar, K., & Oberoi, J. K. (2018). Formulation of cost effective alternative bacterial culture media using fruit and vegetables waste. International Journal of Current Research and Review, 10(2), 6. http://dx.doi.org/10.7324/IJCRR.2018.1022. https://doi.org/ http://dx.doi.org/10.73... ).

A study in India used powdered onion, corn, and garlic skins combined in a culture medium called GCO. Bacteria, such as Bacillus sp., Sarcina sp., P. aeruginosa , and the fungi Candida albicans, Saccharomyces cerevisiae, Penicillium chrysogenum, Aspergillus niger , and Trichoderma viridae, were used to evaluate the efficacy of the GCO medium. According to the authors, the growth of the microorganisms tested using this medium was comparable to that of commercial media, suggesting that this culture medium is economically advantageous for obtaining products from microbial growth ( Berde & Berde, 2015 Berde, C. V., & Berde, V. B. (2015). Vegetable waste as alternative microbiological media for laboratory and industry. World Journal of Pharmacy and Pharmaceutical Sciences, 4(5), 1488-1494. Retrieved from https://storage.googleapis.com/journal-uploads/wjpps/article_issue/1430396310.pdf https://storage.googleapis.com/journal-u... ).

Jadhav et al. (2018) Jadhav, P., Sonne, M., Kadam, A., Patil, S., Dahigaonkar, K., & Oberoi, J. K. (2018). Formulation of cost effective alternative bacterial culture media using fruit and vegetables waste. International Journal of Current Research and Review, 10(2), 6. http://dx.doi.org/10.7324/IJCRR.2018.1022. https://doi.org/ http://dx.doi.org/10.73... analyzed the growth of E. coli , Serratia sp., and Pseudomonas sp. in nine formulations containing varying concentrations of drumstick (Moringa) seeds and peel, orange peel, potato peel, cauliflower stem, and fenugreek stem. The results showed that all formulations allowed the growth of the tested bacteria. Additionally, the bacterial growth in three of the nine formulations was greater than that in commercial nutrient broth.

Alternative media can be used to cultivate microalgae, aimed at biomass production for human consumption and aquaculture. The latter has great economic importance, since microalgae form the basis of the marine food chain, serving as a food source for lobsters, shrimp, and oysters ( Aversari et al., 2018 Aversari, M. N., Nascimento, B. L. A., Martins, N. C., Lucena, R. F. P., & Bonifácio, K. M. (2018). Cultivo de microalgas em meio alternativo e de baixo custo, enriquecido com resíduos de compostagem: uma proposta para melhoria de vida dos pescadores da Paraíba. Revista Brasileira de Gestão Ambiental e Sustentabilidade, 5(10), 969-985. http://dx.doi.org/10.21438/rbgas.051113. http://dx.doi.org/10.21438/rbgas.051113... ).

Brazilian researchers evaluated the potential for growth and biomass production of four microalgae species in different alternative media, including media composed of fruit and vegetable waste (prepared from composting fruit and vegetable waste discarded from distribution markets), sugarcane waste products, and vinasse. The results demonstrated that the medium composed of fruit and vegetable waste was promising for microalgae cultivation as it showed higher productivity than those grown in the control media ( Calixto et al., 2016 Calixto, C. D., Silva Santana, J. K., Lira, E. B., Sassi, P. G. P., Rosenhaim, R., Costa Sassi, C. F., Conceição, M. M., & Sassi, R. (2016). Biochemical compositions and fatty acid profiles in four species of microalgae cultivated on household sewage and agro-industrial residues. Bioresource Technology, 221, 438-446. http://dx.doi.org/10.1016/j.biortech.2016.09.066. PMid:27668876. http://dx.doi.org/10.1016/j.biortech.201... ).

Medeiros et al. (2020) Medeiros, V. P. B., Pimentel, T. C., Varandas, R. C. R., Santos, S. A., Souza Pedrosa, G. T., Costa Sassi, C. F., Conceição, M. M., & Magnani, M. (2020). Exploiting the use of agro-industrial residues from fruit and vegetables as alternative microalgae culture medium. Food Research International, 137, 109722. http://dx.doi.org/10.1016/j.foodres.2020.109722. PMid:33233291. http://dx.doi.org/10.1016/j.foodres.2020... observed similar results when using an alternative, low-cost medium made with a biocomposite of discarded fruits and vegetables to evaluate the cultivation of microalgae isolated from the Northeast of Brazil. They found that, compared with that in the synthetic culture medium, the cultivation of microalgae in this alternative medium facilitated adequate microalgal growth and improved antioxidant activity and mono and polyunsaturated fatty acid production.

4 Alternative media for obtaining microbial products

Although cellulose is commonly produced by plants, some bacteria also produce this polymer, such as those of the genera Gluconacetobacter , Sarcina , and Komagataeibacter . Despite its beneficial applications in industry, the cost of producing bacterial cellulose is very high ( García-Sánchez et al., 2019 García-Sánchez, M. E., Robledo-Ortiz, J. R., Jiménez-Palomar, I., González-Reynoso, O., & González-García, Y. (2019). Production of bacterial cellulose by Komagataeibacter xylinus using mango waste as alternative culture medium. Revista Mexicana de Ingeniería Química, 19(2), 851-865. http://dx.doi.org/10.24275/rmiq/Bio743. http://dx.doi.org/10.24275/rmiq/Bio743... ; Costa et al., 2017 Costa, A. F., Almeida, F. C., Vinhas, G. M., & Sarubbo, L. A. (2017). Production of bacterial cellulose by Gluconacetobacter hansenii using corn steep liquor as nutrient sources. Frontiers in Microbiology, 8, 2027. http://dx.doi.org/10.3389/fmicb.2017.02027. PMid:29089941. http://dx.doi.org/10.3389/fmicb.2017.020... ). In the study by Costa et al. (2017) Costa, A. F., Almeida, F. C., Vinhas, G. M., & Sarubbo, L. A. (2017). Production of bacterial cellulose by Gluconacetobacter hansenii using corn steep liquor as nutrient sources. Frontiers in Microbiology, 8, 2027. http://dx.doi.org/10.3389/fmicb.2017.02027. PMid:29089941. http://dx.doi.org/10.3389/fmicb.2017.020... , alternative media formulated with waste products from the food industry, such as sugarcane molasses and corn steeping liquor, were assessed for their efficiency in promoting cellulose production by a strain of Gluconacetobacter hansenii . The alternative medium containing cane molasses produced unsatisfactory results. However, the medium with corn steeping liquor provided the highest yield of dry and hydrated bacterial cellulose mass, having an efficiency of approximately 73% of that obtained with the commercial medium.

Recently, a Mexican study investigated the potential of mango pulp as an alternative culture medium for cellulose production by Komagataei bacterxylinus . The chemical structure and thermal degradation of bacterial cellulose produced in the mango pulp-based culture medium were comparable with those of cellulose produced in pure sugars. Thus, the authors state that cellulose production in this alternative medium is viable and achieves a high yield. In addition, regarding sustainability, this process takes advantage of an agrifood excess generated in several countries and contributes to the reduction of bacterial cellulose production costs ( García-Sánchez et al., 2019 García-Sánchez, M. E., Robledo-Ortiz, J. R., Jiménez-Palomar, I., González-Reynoso, O., & González-García, Y. (2019). Production of bacterial cellulose by Komagataeibacter xylinus using mango waste as alternative culture medium. Revista Mexicana de Ingeniería Química, 19(2), 851-865. http://dx.doi.org/10.24275/rmiq/Bio743. http://dx.doi.org/10.24275/rmiq/Bio743... ).

Lipases are enzymes that catalyze the hydrolysis of triacylglycerol ester linkages, generating free fatty acids and glycerol. These microbial enzymes are widely used in industrial food, organic, and pharmaceutical synthesis. Microbial lipase production in alternative media was described in a study carried out in Portugal. In this work aiming to produce lipases from Candida rugosa , the authors used alternative culture media composed of varied concentrations of cane molasses, millets, and Russian water (a byproduct of olive oil extraction). It was observed that the medium containing molasses, millets, and Russian waters in concentrations of 1%, 0.4%, and 0.1%, respectively, produced lipases, suggesting that these products can be used for the production of enzymes, substantially reducing culture media costs ( Freitas et al., 2016 Freitas, M., Gudiña, E. J., Silvério, S. C., Rodrigues, L. R., & Gonçalves, L. R. B. (2016). Produção de lipase a partir de Candida rugosa NRRL Y-95 utilizando meio de cultura contendo resíduos agroindustriais. In Anais do XXI Congresso Brasileiro de Engenharia Química. Fortaleza. Retrieved from http://repositorium.sdum.uminho.pt/bitstream/1822/44520/1/document_46604_1.pdf http://repositorium.sdum.uminho.pt/bitst... ).

Mohammed et al. (2020) Mohammed, B. B., Shatti, Z. O., Jasim, E. I., Dari, W. A., & Alfraji, N. (2020). Local culture medium from the legumes mixture as a novel media for the growth and stimulation of prodigiosin pigment which production from Serratia marcescens that isolated environmentally. Plant Archives, 20(1), 991-1000. Retrieved from http://www.plantarchives.org/SPECIAL%20ISSUE%2020-1/991-1000%20(242).pdf http://www.plantarchives.org/SPECIAL%20I... used mixtures of legumes to compose a medium that stimulated the production of prodigiosin pigments in Serratia marcescens . The medium was prepared from seven different legume powders: white beans, fava beans, mung beans, peas, chickpeas, black beans, and lentils. The solid and liquid forms of the alternative culture medium stimulated pigment production during incubation at 25-28 °C for 24 h. The authors also tested media of the seven legumes individually to verify the pigment production; however, they observed a decrease in prodigiosin production, with the colonies becoming light red in color. The medium prepared from the combination of legumes proved to be easy to prepare and store. In addition, it was highly effective in stimulating the production of S. marcescens pigments, with the advantage that its constituents are available at a low cost.

5 Conclusion

In view of various scientific experiments, developing effective and low-cost culture media is a possibility. Many of these media use food items or parts thereof that are not used for human consumption, making them accessible to institutions within sufficient resources for commercial culture media. In addition to promoting accessibility to knowledge, the development of alternative culture media contributes to sustainability by using food waste. Most studies highlight the effectiveness of alternative culture media, indicating similar applicability and, in some cases, superior performance as compared to the traditional culture media. Thus, studies evaluating unexplored food and food waste in this way are promising.

• Practical Application: This work provide scientific basis for, and encourage the development and use of alternative culture media.
• Alves, I. D. S., Tavares, P. D. S., Lima, J. D. S., Duarte, N., & Gava, C. (2016). Hidrolisado de proteína de soja em meio de cultivo para a produção de agente de controle biológico. In Anais da Jornada de Iniciação Científica da Embrapa Semiárido. Brasília: Embrapa.
• Andrade, C. P. (2017). Meios de cultura alternativos para a produção de biomassa de Pleurotus eryngii (Trabalho de conclusão de curso). Universidade do Estado do Amazonas, Manaus.
• Aversari, M. N., Nascimento, B. L. A., Martins, N. C., Lucena, R. F. P., & Bonifácio, K. M. (2018). Cultivo de microalgas em meio alternativo e de baixo custo, enriquecido com resíduos de compostagem: uma proposta para melhoria de vida dos pescadores da Paraíba. Revista Brasileira de Gestão Ambiental e Sustentabilidade , 5(10), 969-985. http://dx.doi.org/10.21438/rbgas.051113 » http://dx.doi.org/10.21438/rbgas.051113
• Berde, C. V., & Berde, V. B. (2015). Vegetable waste as alternative microbiological media for laboratory and industry. World Journal of Pharmacy and Pharmaceutical Sciences , 4(5), 1488-1494. Retrieved from https://storage.googleapis.com/journal-uploads/wjpps/article_issue/1430396310.pdf » https://storage.googleapis.com/journal-uploads/wjpps/article_issue/1430396310.pdf
• Caldeirão, L., Bosso, A., Tomal, A. A. B., Busanello, M., & Spinosa, W. A. (2015). Avaliação do desenvolvimento de bactérias lácticas em melaço de soja. Blucher Biochemistry Proceedings , 1(2), 369. http://dx.doi.org/10.5151/biochem-vsimbbtec-22158 » http://dx.doi.org/10.5151/biochem-vsimbbtec-22158
• Calixto, C. D., Silva Santana, J. K., Lira, E. B., Sassi, P. G. P., Rosenhaim, R., Costa Sassi, C. F., Conceição, M. M., & Sassi, R. (2016). Biochemical compositions and fatty acid profiles in four species of microalgae cultivated on household sewage and agro-industrial residues. Bioresource Technology , 221, 438-446. http://dx.doi.org/10.1016/j.biortech.2016.09.066 PMid:27668876. » http://dx.doi.org/10.1016/j.biortech.2016.09.066
• Cattelan, A. J., & Dall’Agnol, A. (2018). The rapid soybean growth in Brazil. Oilseeds & Fats Crops and Lipids , 25(1), D102. https://doi.org/10.1051/ocl/2017058 » https://doi.org/10.1051/ocl/2017058
• Costa, A. F., Almeida, F. C., Vinhas, G. M., & Sarubbo, L. A. (2017). Production of bacterial cellulose by Gluconacetobacter hansenii using corn steep liquor as nutrient sources. Frontiers in Microbiology , 8, 2027. http://dx.doi.org/10.3389/fmicb.2017.02027 PMid:29089941. » http://dx.doi.org/10.3389/fmicb.2017.02027
• Costa, R. S., Santos, O. V., Lannes, S. C. S., Casazza, A. A., Aliakbarian, B., Perego, P., Ribeiro-Costa, R. M., Converti, A., & Silva, J. O. C. Jr. (2020). Bioactive compounds and value-added applications of cupuassu ( Theobroma grandiflorum Schum.) agroindustrial by-product. Food Science and Technology , 40(2), 401-407. http://dx.doi.org/10.1590/fst.01119 » http://dx.doi.org/10.1590/fst.01119
• Cruz, C. H. S., Santos, J. B., Santos, F. P., Silva, G. M. M., Cruz, E. F. N., Ramos, G. L. P. A., & Nascimento, J. S. (2020). Texturized soy protein as an alternative low-cost media for bacteria cultivation. Bacterial Empire , 3(4), 74-76. http://dx.doi.org/10.36547/be.2020.3.4.74-76 » http://dx.doi.org/10.36547/be.2020.3.4.74-76
• Freitas, M., Gudiña, E. J., Silvério, S. C., Rodrigues, L. R., & Gonçalves, L. R. B. (2016). Produção de lipase a partir de Candida rugosa NRRL Y-95 utilizando meio de cultura contendo resíduos agroindustriais. In Anais do XXI Congresso Brasileiro de Engenharia Química. Fortaleza. Retrieved from http://repositorium.sdum.uminho.pt/bitstream/1822/44520/1/document_46604_1.pdf » http://repositorium.sdum.uminho.pt/bitstream/1822/44520/1/document_46604_1.pdf
• Gabunia, K., Deslate, H. M., & Garcia, J. (2019). Effectiveness of corn husk extract as an alternative culture media for the growth of Escherichia coli and Staphylococcus aureus. Biology and Life Sciences , 39(2), 4. Retrieved from https://ijrp.org/paper-detail/758 » https://ijrp.org/paper-detail/758
• García-Sánchez, M. E., Robledo-Ortiz, J. R., Jiménez-Palomar, I., González-Reynoso, O., & González-García, Y. (2019). Production of bacterial cellulose by Komagataeibacter xylinus using mango waste as alternative culture medium. Revista Mexicana de Ingeniería Química , 19(2), 851-865. http://dx.doi.org/10.24275/rmiq/Bio743 » http://dx.doi.org/10.24275/rmiq/Bio743
• Jadhav, P., Sonne, M., Kadam, A., Patil, S., Dahigaonkar, K., & Oberoi, J. K. (2018). Formulation of cost effective alternative bacterial culture media using fruit and vegetables waste. International Journal of Current Research and Review , 10(2), 6. http://dx.doi.org/10.7324/IJCRR.2018.1022. » https://doi.org/ http://dx.doi.org/10.7324/IJCRR.2018.1022
• Leira, M. H., Nascimento, A. F., Alves, F. R., Orfao, L., Lacerda, Y. G., Botelho, H. A., Reghim, L., & Lago, A. A. (2019). Characterization of different techniques for obtaining minced fish from tilapia waste. Food Science and Technology , 39(1, Suppl. 1), 63-67. http://dx.doi.org/10.1590/fst.37517 » http://dx.doi.org/10.1590/fst.37517
• Medeiros, V. P. B., Pimentel, T. C., Varandas, R. C. R., Santos, S. A., Souza Pedrosa, G. T., Costa Sassi, C. F., Conceição, M. M., & Magnani, M. (2020). Exploiting the use of agro-industrial residues from fruit and vegetables as alternative microalgae culture medium. Food Research International , 137, 109722. http://dx.doi.org/10.1016/j.foodres.2020.109722 PMid:33233291. » http://dx.doi.org/10.1016/j.foodres.2020.109722
• Mohammed, B. B., Shatti, Z. O., Jasim, E. I., Dari, W. A., & Alfraji, N. (2020). Local culture medium from the legumes mixture as a novel media for the growth and stimulation of prodigiosin pigment which production from Serratia marcescens that isolated environmentally. Plant Archives , 20(1), 991-1000. Retrieved from http://www.plantarchives.org/SPECIAL%20ISSUE%2020-1/991-1000%20(242).pdf » http://www.plantarchives.org/SPECIAL%20ISSUE%2020-1/991-1000%20(242).pdf
• Navarro-Peraza, R. S., Osuna-Ruiz, I., Lugo-Sánchez, M. E., Pacheco-Aguilar, R., Ramírez-Suárez, J. C., Burgos-Hernández, A., Martínez-Montaño, E., & Salazar-Leyva, J. A. (2020). Structural and biological properties of protein hydrolysates from seafood by-products: a review focused on fishery effluents. Food Science and Technology , 40(1, Suppl. 1), 1-5. http://dx.doi.org/10.1590/fst.24719 » http://dx.doi.org/10.1590/fst.24719
• Ramírez, J. A., Castañón-Rodríguez, J. F., & Uresti-Marín, R. M. (2020). An exploratory study of possible food waste risks in supermarket fruit and vegetable sections. Food Science and Technology In press. http://dx.doi.org/10.1590/fst.27320 » http://dx.doi.org/10.1590/fst.27320
• Ravimannan, S. P., & Pathmanathan, S. (2016). Soy flour as alternative culture media for yeasts. Global Journal of Science Frontier Research , 16(3), 75-78. Retrieved from https://globaljournals.org/item/6617-soy-flour-as-alternative-culture-media-for-yeasts » https://globaljournals.org/item/6617-soy-flour-as-alternative-culture-media-for-yeasts
• Rouf, A., Kanojia, V., Naik, H. R., Naseer, B., & Qadri, T. (2017). An overview of microbial cell culture. Journal of Pharmacognosy and Phytochemistry , 6(6), 1923-1928. Retrieved from https://www.phytojournal.com/archives/?year=2017&vol=6&issue=6&ArticleId=2312 » https://www.phytojournal.com/archives/?year=2017&vol=6&issue=6&ArticleId=2312
• Shareef, S. A. (2019). Formulation of alternative culture media from natural plant protein sources for cultvation of different bacteria and fungi. Zanco Journal of Pure and Applied Sciences , 31(4), 61-69. http://dx.doi.org/10.21271/zjpas.31.4.7 » http://dx.doi.org/10.21271/zjpas.31.4.7
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• Uthayasooriyan, M., Pathmanathan, S., Ravimannan, N., & Sathyaruban, S. (2016). Formulation of alternative culture media for bacterial and fungal growth. Der Pharmacia Lettre , 8(1), 431-436. Retrieved from https://www.scholarsresearchlibrary.com/articles/formulation-of-alternative-culture-media-for-bacterial-and-fungal-growth.pdf » https://www.scholarsresearchlibrary.com/articles/formulation-of-alternative-culture-media-for-bacterial-and-fungal-growth.pdf

Publication Dates

• Publication in this collection 26 May 2021
• Date of issue 2022
• Received 08 Jan 2021
• Accepted 16 Jan 2021

• http://orcid.org/0000-0001-5631-9668
• * Corresponding author: [email protected]

SCIMAGO INSTITUTIONS RANKINGS

Table 1   products of vegetable origin and waste from hortofruticulture used in the composition of different alternative culture media., how to cite, pdf version for download, related articles.

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Research Journal of Pharmacology and Pharmacodynamics

2321-5836 (Online) 0975-4407 (Print)

A Novel Bacterial Culture Media: Fruit Waste Agar

Author(s): Dhiraj S. Girase , Rahulsing G. Girase , Prasad P. Girase , Neha R. Jaiswal

Email(s): [email protected]

Address: Dhiraj S. Girase*, Rahulsing G. Girase, Prasad P. Girase, Neha R. Jaiswal Department of Microbiology, Ahinsa Institute of Pharmacy, Dhule Road, Dondaicha, 425408. *Corresponding Author

Published In:   Volume -  14 ,      Issue -  4 ,     Year -  2022

ABSTRACT: The development of microbiology began in the 19th century with the invention of the culture medium. Bacterial culture was the first method to study human microbiota in 1860. Louis pasteur was the first to propagate bacteria on culture media. The culture media provides the essential nutrients such as carbohydrates, protein, vitamins and some growth factors for the proper development of bacteria. Nowadays, these growth medias are prepared by different expensive chemical ingredients in laboratories for research experiments, which ultimately makes our experiments expensive. Instead of using high-cost culture media, fruit waste material could prove to be a good alternate source for the production of low-cost media. The waste generated in household practices and kitchen includes vegetables and fruit waste. It is waste that almost every house generates every day. It can serve as a good source of nutrients and vitamins for in microorganisms. Hence these materials can be used to formulate solid media for the growth of bacteria. In the current study waste material like mango peels, banana peels, lemon peels and ground nut shell have been included to formulate the media. This material was collected from kitchen waste and vegetable market. Comparing the growth of organism (lactobacillus bulgaricus) standard commercial media and fruit waste with agar, it was found that the media prepared from fruit waste serves as a good and inexpensive source of nutrients for many bacteria. Thus, it can good be feather and used commercially for isolation and cultivation of various microorganisms.

• Culture media
• Fruit waste
• Lactobacillus bulgaricus.

Cite this article: Dhiraj S. Girase, Rahulsing G. Girase, Prasad P. Girase, Neha R. Jaiswal. A Novel Bacterial Culture Media: Fruit Waste Agar. Research Journal of Pharmacology and Pharmacodynamics.2022;14(4):225-8. doi: 10.52711/2321-5836.2022.00039 Cite(Electronic): Dhiraj S. Girase, Rahulsing G. Girase, Prasad P. Girase, Neha R. Jaiswal. A Novel Bacterial Culture Media: Fruit Waste Agar. Research Journal of Pharmacology and Pharmacodynamics.2022;14(4):225-8. doi: 10.52711/2321-5836.2022.00039   Available on: https://rjppd.org/AbstractView.aspx?PID=2022-14-4-5

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The French Journal of Media Studies

Accueil Numéros 5 Media and Diversity The Concept of Culture in Media S...

The Concept of Culture in Media Studies: A Critical Review of Academic Literature

This study examines the way culture has been researched in media studies and suggests how critical intercultural communication could contribute to the field. A literature review was conducted and articles (N=114) published in peer-reviewed journals between 2003 and 2013 were collected. Results show that studies dealing with media and culture do not systematically define the concept of culture. Findings also indicate that culture is oftentimes taken for granted instead of being problematized and addressed as a source of struggle. Advantages of using a critical intercultural communication framework to examine culture are discussed.

Entrées d’index

Keywords: , texte intégral.

• 1 Debra L. Merskin, Media, Minorities, and Meaning: A Critical Introduction (New York: Peter Lang Pub (...)
• 2 Robert M. Entman, “Framing Bias: Media in the Distribution of Power,” Journal of Communication 57, (...)
• 3 Sari Pietikäinen and Helen Kelly-Holmes, “The Dangers of Normativity – The Case of Minority Languag (...)
• 4 Isabelle Rigoni, “Intersectionality and Mediated Cultural Production in A Globalized Post-Colonial (...)

1 Recent directions in the field of media studies have turned culture into a significant object of study. Strong emphasis has been put on representations of minorities in media 1 and their potential biases, 2 minority-language media 3 and ethnic media. 4 However, the increasing attention given to culture has not gone hand in hand with an overall clarification of the concept itself. Defining culture remains a difficult exercise, especially because of its multifaceted nature. The importance of the concept in media studies and its blurry theoretical grounds highlight the need to look back at how it has been used in studies. The present article is built around three main questions. First, it looks at how culture has been researched in media studies . Second, it examines possible limitations of these approaches. Third, it investigates ways in which a critical intercultural communication framework can be beneficial to media studies dealing with culture. For this purpose, this study explores recent academic discourse on media and culture by reviewing studies dealing with issues of cultural diversity, representations of culture, and discourse of culture. In addition to examining approaches to culture and their potential limitations, this article also presents ways in which critical intercultural communication can be used by researchers from different disciplines interested in culture.

2 This article starts by presenting some of the main arguments raised in discussing the use and conceptualization of culture. The way critical intercultural communication contributes to this discussion is presented, followed by reasons why it can be a relevant framework for media studies. This article then looks at previous reviews of academic discourse, especially focusing on the fields of communication and media. Methods for collecting data are detailed before discussing the findings and main implications of this study .

The Concept of Culture

• 5 Robert Brightman, “Forget Culture: Replacement, Transcendence, Relexification,” Cultural Anthropolo (...)
• 6 William H. Sewell Jr, “The Concept(s) of Culture,” in Practicing History: New Directions in Histori (...)
• 7 Ingrid Piller, Intercultural Communication: A Critical Introduction (Edinburgh: Edinburgh Universit (...)
• 9 Fred Dervin, “Approches dialogiques et énonciatives de l’interculturel : Pour une didactique des la (...)
• 10 Fred Dervin, “A Plea for Change in Research on Intercultural Discourses: A “Liquid” Approach to the (...)
• 11 Sylvie Poirier, “La (dé)politisation de la culture? Réflexions sur un concept pluriel, ” Anthropolog (...)
• 12 Ryuko Kubota, “Critical Approaches to Intercultural Discourse and Communication,” in The Handbook o (...)

3 Culture is a concept that has been discussed extensively, giving rise to multiple approaches and uses of the term across fields of study. As the concept of culture became increasingly important and pervasive, it also became increasingly questioned. Across different fields of studies, scholars discuss whether to keep, change or altogether discard the concept of culture. Brightman brought together some of the main criticisms addressed to culture. 5 His work reveals the variety of arguments used against the concept and the lack of convergence on how to revise it or what to use instead. Sewell also goes through some of the cornerstone issues in conceptualizing culture. 6 The first distinction he mentions, and which he argues is not always explicitly made by researchers, is the one between the use of culture and cultures . The singular use refers to the theoretical approach used for research while the plural use refers to the object of study . Culture is used in contrast to other academic disciplines or analytical tools (e.g. politics, economics) whereas cultures is used when examining different forms of culture and is therefore more concrete (e.g. regional culture, hipster culture). Another distinction which has had a strong impact on the study of culture is the understanding of culture as practice or culture as a system of symbols and meanings . Critical intercultural scholars regard culture as a discursive construction, emphasizing the role played by individuals in performing culture. Inherited from constructionism, this approach emphasizes culture as something people do rather than something people have. 7 Regarding culture as practice is the dominant approach in critical intercultural communication, which tends to be used in opposition to culture as a system of symbols and meanings. This latter approach to culture is often associated with essentialist and positivist views that describe culture as an identifiable and fixed item. 8 Essentialist views of culture have been criticized for pinpointing aspects of cultures (typically reduced to the idea of national cultures) and presenting such characteristics as truths rather than constructions. 9 On the other hand, critical intercultural scholars argue for an approach to culture that is largely embedded within social constructionism. 10 Such an approach emphasizes culture as constructed, political, intertwined with ethics 11 and related to power both within and between societies. 12 From that perspective, culture is understood to be situated rather than objective, and ever changing as opposed to stable.

• 13 Stuart Hall, “Introduction,” in Representation: Cultural Representations and Signifying Practices , (...)

14 Shi-Xu, A Cultural Approach to Discourse (New York: Palgrave Macmillan, 2005), 1–13.

• 15 William A. Gamson and Andre Modigliani, “Media discourse and Public Opinion on Nuclear Power: A Con (...)
• 16 Nancy K. Rivenburgh, “Media Framing of Complex Issues: The Case of Endangered Languages,” Public Un (...)
• 17 Ulrika Olausson, “Global warming – Global Responsibility? Media Frames of Collective Action and Sci (...)

4 As Hall stresses, culture is about meaning and as such “permeates all of society.” 13 Representations, practices, values and identities have cultural meanings that are discursively constructed and tap into previous cultural discourses to be meaningful. Critical intercultural communication casts light on ways in which meanings echo cultural knowledge and are therefore difficult to identify and question – even for researchers themselves, hence a strong emphasis placed on reflexivity. 14 The importance of “cultural resonance” has also been pointed out by scholars examining media frames. 15 Rivenburgh stresses the way “media frames that reflect cultural common sense, values, or ideology are both instinctually employed by journalists and easily accepted by the public”. 16 Tapping into cultural resonance may be done consciously or out of habit by journalists and editors who see their cultural environment as natural. The use of culturally resonant frames in media discourse increases their taken-for-grantedness, which enhances their power. Cultural markers create a sense of common sense because of their presence in everyday life experiences which contributes to normalizing them, making them “well-nigh impossible to recognize, question, or resist”. 17 The emphasis that critical intercultural communication puts on culture as having the propensity to normalize representations and practices thus appears especially relevant to media studies.

• 18 Marianne Jørgensen and Louise J. Phillips, Discourse Analysis as Theory and Method (London: Sage Pu (...)

19 Chris Barker, The Sage Dictionary of Cultural Studies (London: Sage Publications, 2004), 64–65.

5 Another aspect where interests of both disciplines meet is the extent to which discursive practices can be ethnocentric. To different extents, critical scholars agree on the idea that discourses construct the way societies represent themselves. 18 Media discourse is probably one of the discursive practices most often cited as constitutive of people’s worldviews, representations of themselves and others. One question put forward by critical intercultural communication is the extent to which such discourses rely on ethnocentric representations. Ethnocentrism refers to people’s tendency to use the standards of their own culture to judge other cultural groups, which is concurrent with people’s tendency to regard their culture as superior to others. 19 Ethnocentrism thus refers to the way cultural standards can pass as implicit norms for people identifying with that culture. As much emphasis is now put on ethnic media, cultural diversity and the effects of globalization on developing transnational media spaces, it is important not to overlook the extent to which national media discourse can still be limited and convey ethnocentric representations. The emphasis put on ethnocentrism in media has strong practical implications for professionals and audiences by encouraging them to be more critical towards news content.

Examining Academic Discourse

• 20 Keith V. Erickson, Cathy A. Fleuriet and Lawrence A. Hosman, “Prolific Publishing: Professional and (...)
• 21 Michael W. Kramer, Jon A. Hess and Loren D. Reid, “Trends in Communication Scholarship: An Analysis (...)

22 Jørgensen and Phillips, Discourse Analysis as Theory and Method , 175–177.

• 23 Maggie MacLure, Discourses in Educational and Social Research ( Buckingham: Open University Press, 2 (...)

6 Conferences and publications are the main venues for academics to discuss the latest developments and findings from all disciplines. Nowadays, academic debate mostly takes place in journals, whose number has kept on increasing throughout the last decades. 20 It is through these journals that most ideas are expressed, hence the importance of examining their content. Publishing is central for scholars, not only as a way of contributing to the development of their fields of study but also to the development of their career. The notorious “publish or perish” phrase provides an efficient summary of what publications nowadays represent in the academic world. 21 As journal articles have become the main venue for academic discourse, they have also turned into common and natural venues. Such development can be problematic if academic discourse comes to be granted too much legitimacy instead of having its status, form and content constantly challenged. Like other discursive practices, journal articles create and validate certain meanings that progressively become the norm and can, as such, easily pass as natural instead of constructed and contingent. 22 Knowledge expressed in academic discourse is therefore not objective but is, like any other form of knowledge, “‘situated’ – that is, produced by and for particular interests, in particular circumstances, at particular times”. 23 Reflexivity, a central ethical component of research, is therefore especially important when looking at academic discourse as a whole.

• 24 Ronald D. Gordon, “Beyond the Failures of Western Communication Theory,” Journal of Multicultural D (...)
• 25 Molefi Kete Asante, “The Ideological Significance of Afrocentricity in Intercultural Communication, (...)
• 26 Yoshitaka Miike, “Non-Western Theory in Western research? An Asiacentric Agenda for Asian Communica (...)
• 27 Yoshitaka Miike, “An Asiacentric Reflection on Eurocentric Bias in Communication Theory,” Communica (...)

28 Asante, “The Ideological Significance of Afrocentricity in Intercultural Communication,” 10.

• 29 Shi-Xu, “Reconstructing Eastern Paradigms of Discourse Studies ,” Journal of Multicultural Discourse (...)
• 30 Hui-Ching Chang, Rich Holt and Lina Luo, “Representing East Asians in Intercultural Communication T (...)
• 31 Molefi Kete Asante, Afrocentricity: The Theory of Social Change (Chicago: African American Images, (...)
• 32 Ella Shohat and Robert Stam, Unthinking Eurocentrism: Multiculturalism and the Media (London: Routl (...)
• 33 Eric Kit-Wai Ma, “Rethinking Media Studies: The Case of China,” in De-westernizing Media Studies , e (...)

7 Recently, increasing attention has been paid to cultural bias in academic discourse. Some scholars especially criticize the general lack of attention paid to such bias. Gordon, for instance, has looked at communication theories, which he describes as an example of a Western-oriented or Eurocentric approach to research. 24 Gordon highlights the way communication theories have typically been elaborated by Caucasian researchers from the United States who mostly used university students as participants. Western-oriented theories have been criticized for being taken as universally valid despite being anchored in European academic traditions, especially the heritage of the Enlightenment period. In response, some scholars have suggested using different approaches. Asante has, for instance, put forth Afrocentricity as an ideological and methodological approach to conduct research from an African standpoint. 25 Similarly, Miike encourages using Asiacentricity to examine Asian contexts from an Asian perspective. 26 Miike details ways in which the concept of “communication” is defined differently by Asiacentric and Eurocentric approaches, as different aspects and outcomes are emphasized. 27 Afrocentricity and Asiacentricity illustrate ongoing efforts to diversify analytical tools that would help research human activity and capture its plurality. These approaches are meant to open up new perspectives in research by providing scholars with different outlooks on their objects of study. For some scholars, developing new approaches is also meant to create legitimate alternatives to Western theories. Back in 1983, Asante, for instance, pointed out the difficulty for some African scholars to be published in Eurocentric journals because of their different, and non-valued, academic tradition. 28 Shi-Xu advocates the emergence of various academic paradigms that would work “as equal but distinctive interlocutors” and help “redress this cultural imbalance”. 29 However, other voices among academics are more reserved when it comes to developing culture-specific approaches, fearing that it will only turn the problem around instead of solving it. Chang, Holt and Luo raise the question as they discuss Asiacentricity: “If every version of a cultural writing of other is at the same time also the construction of self , might our call for an Asiacentric perspective in explaining communication not fall into the same trap as the often-blamed Eurocentric perspective? Might the reversal of the situation – prioritizing Asians – encounter the same predicament?” 30 Supporters of culture-specific approaches, however, embrace this criticism. From their perspective, culture-specific approaches are beneficial because they are explicitly situated and do not try to reach universal validity. They point out that it is not so much Western-oriented theories being biased and situated that triggered critics as the lack of reflexivity about these limitations. 31 Similar debates are also taking place among media scholars, with issues of “de-Westernizing” media studies being increasingly discussed. 32 Critics claim that Western-oriented media theories are too limited as they are based on European and North American political, economic and media models. Looking specifically at China, Ma argues for a compromise. 33 He questions the benefits of new theories that would risk “essentializing and exoticizing the Asian experience” and proposes adjusting existing theories to fit the Chinese context.

Methods and Results

8 A literature review was conducted in fall 2013 using the academic search engines EBSCO and Web of Science. The keywords “media representation”, “media discourse”, “diversity”, and “cultur*” (the asterisk was used to include other possible endings in the data search) were used to collect peer-reviewed articles published in English between 2003 and 2013. Only articles dealing with issues of cultural diversity and media were included. Some articles in which culture was understood from an agricultural perspective were, for instance, left out. The search was ended once saturation was reached, that is when the same keywords used in different search engines brought up the same articles. In total, 114 articles were collected and reviewed for the purpose of this study. The literature review was conducted inductively and kept as open as possible. The search was not limited to any specific journals because the scope of topics covered by media studies on cultural diversity was expected to be very wide. One aim of this literature review being to see what types of issues were encompassed, it would have been detrimental to limit the search to certain journals.

• 34 See for example Gordon, “Beyond the Failures of Western Communication Theory,” and Miike, “An Asiac (...)
• 35 Annelies Verdoolaege, “Media representations of the South African Truth and Reconciliation Commissi (...)
• 36 Jawad Syed, “The Representation of Cultural Diversity in Urdu-Language Newspapers in Pakistan: A St (...)
• 37 Yasmin Jiwani, “War Talk Engendering Terror: Race, Gender and Representation in Canadian Print Medi (...)
• 38 Fabienne Darling-Wolf, “Sites of Attractiveness: Japanese Women and Westernized Representations of (...)
• 39 Maria Andrea Dos Santos Soares, “Look, Blackness in Brazil!: Disrupting the Grotesquerie of Racial (...)
• 40 Anna Bredström, “Gendered Racism and the Production Of Cultural Difference: Media Representations a (...)
• 41 Shanara Rose Reid-Brinkley, “Ghetto Kids Gone Good: Race, Representation, and Authority in the Scri (...)

9 Short descriptions were written about each article to describe their content, which later helped identify recurrent themes, similar approaches and unusual topics. Articles were collected within a 10-year time frame in order to get an overall picture of the state of recent research. No particular evolution or trends were noticed, however, regarding approaches or topics tackled. Oftentimes, authors used eclectic theoretical and/or methodological approaches that, for instance, combined cultural studies and critical discourse analysis (CDA) or feminist theories and CDA. Among studies that explicitly presented their theoretical and/or methodological frameworks, CDA (9%), feminist theories (10%) and cultural/critical frameworks relying on Foucault’s, Gramsci’s or Hall’s theories (29%) were recurrent approaches. As regards analytical tools from journalism or media studies, results indicated that framing theory (10%) was often used as opposed to gatekeeping or agenda-setting theory (2%). Similarly to results from previous reviews of academic discourse, 34 studies from this data set appeared to be mainly conducted from a Western-oriented perspective. This was the case even for strongly situated studies that focused on particular cultures and were published in specific journals. For instance, the article “Media Representations of the South African Truth and Reconciliation Commission and Their Commitment to Reconciliation” 35 was published in the Journal of African Cultural Studies using CDA, and the article “The Representation of Cultural Diversity in Urdu-Language Newspapers in Pakistan: A Study of Jang and Nawaiwaqt” 36 was published in the South Asia Journal of South Asian Studies and used Hodder’s approach. In comparison, articles looking at representations of women were found to use various trends of feminist theories such as standpoint theory, 37 postcolonial theory 38 and black feminism. 39 Similarly, articles explicitly dealing with race, for instance, used postcolonial theory 40 and Jackson’s (2006) theory of scripting and media framing of black bodies. 41

42 Kathryn Woodward, Identity and Difference (London: Sage Publications, 1997), 35.

10 As regards the scope of topics tackled, results indicated that the majority of articles investigated representation of minorities in the media (67%), most often dealing with ethnic or religious groups. Articles within this category oftentimes raised the issue of media stereotyping and othering minorities. That is, studies investigated ways in which media discourse sometimes supports the construction of minorities as “Others”, which can emphasize differences between groups and convey negative stereotypical representations. 42 Among articles exploring representations of minorities, several studies dealt with sport and representations of athletes (8%). A significant number of studies examined discourses of diversity (23%), with some focusing exclusively on European discourses of diversity (3%). Other studies investigated what diversity stands for in the media and how it can be approached by newsrooms. On the other hand, some topics appeared to be scarcely tackled, which was the case of foreign-news coverage (4%), newsroom diversity (2%) or integration and acculturation issues (2%). Regarding the type of media investigated, the majority of studies examined newspapers and television (70%), while entertainment and advertisement (19%) were less considered.

Culture: Between Main Focus and Transparent Background

11 Despite explicitly dealing with culture, many articles did not provide a clear definition of the term. Nor did many researchers position themselves as regards the different schools of thought on culture. Instances of culture taken for granted particularly occurred in the literature when (1) culture was associated with nations or (2) the so-called Western world, or (3) when the concepts of race or ethnicity were used.

43 Michael Billig, Banal Nationalism (London: Sage Publications, 1995), 6.

• 44 Rona T. Halualani, S. Lily Mendoza and Jolanta A. Drzewiecka, “‘Critical’” Junctures in Intercultur (...)

12 Results from the literature review conducted for this study indicate the recurrent association of culture with that of nation. However, the use of countries as cultural contexts and embodiments of cultures can be problematic for several reasons. A main pitfall is the homogeneous and reduced picture of culture that it conveys. Culture is a multilayered notion and reducing it to the single aspect of nationality can be detrimental to both the idea of nation and culture. Nations are multicultural, in the literal meaning of the word: that is, made out of multiple cultures. Studies that use nation as the unit of reference to talk about culture, language and identity tend to homogenize national cultures and therefore increase chances of being stereotypical instead of deconstructing stereotypes. A second important drawback is the way national culture tends to be presented as normal instead of artificial. This contributes to discourses of “banal nationalism” where individuals are brought up with the idea that the world is divided between nations. 43 It also overlooks the fact that culture is constructed and thus intertwined with power and struggle. When culture is understood as the equivalent of nation, it typically hints at the culture of the dominant group within that nation. Such representation leaves out or even marginalizes other forms of culture within that country, therefore maintaining existing hierarchy instead of deconstructing it. Halualani, Mendoza and Drzewiecka point out the danger of blurring the lines between the concepts of culture and nation: “To accept cultures as nations as inherently and naturally truthful and accurate at a surface level would be to risk reproducing external framings of cultural groups advanced by colonialist governments, dominant nationalist parties, and ruling power interests that benefit from such ‘status quo’ thinking.” 44

45 Piller, Intercultural Communication: A Critical Introduction , 66–69.

46 Dervin, “A Plea For Change in Research on Intercultural Discourses,” 41.

13 Associating culture to nation thus tends to sustain hierarchy between cultural practices and those who practice or identify to them. By maintaining hierarchical order between cultures, the nation approach implicitly contributes to preserving the persistent dichotomy between “us” and “them”, whether within or between nations. The nation approach to culture is tightly related to essentialist views of culture in that it provides a static and homogeneous picture of culture. Essentialism regards culture as a one-dimensional concept and therefore leaves out issues of race, religion, gender, social status and larger historical and political structures. Critical intercultural communication endeavors to go beyond such limitations by taking into account the multidimensional, constructed, contingent and dynamic facets of culture. The critical intercultural communication approach does not dismiss nations as possible instances of cultures. However, it focuses on exploring which representations of culture and nation are associated, through which processes, and whether such associations vary in time or depending on the context. Critical intercultural scholars emphasize culture as raising questions rather than providing answers that would help predict people’s behaviors. 45 Through its conceptualization of culture, a critical intercultural communication framework helps focus on ways in which people construct their sense of cultural belonging and identity. 46 This approach is relevant to media studies in many ways. It is strongly related to research exploring the relation individuals make between their media consumption and their identity, or research dealing with the way media discourse is intertwined with discourses of (national) identity. The emphasis put on constructing cultural identity and belonging can also help focus on who is represented as “belonging” and who is not, which is a significant aspect of studies on minority media and cultural diversity.

• 47 Malcom D. Brown, “Comparative Analysis of Mainstream Discourses, Media Narratives and Representatio (...)
• 48 Margarida Carvalho, “The Construction of the Image of Immigrants and Ethnic Minorities in Two Portu (...)

14 As mentioned beforehand, results indicated that culture can be taken for granted when it is about “us”. In many cases, “our” culture is used as a background for research, making it look normal and neutral. “Our” culture also appears homogeneous because examining diversity oftentimes consists of examining the “Other”. For instance, the article entitled “Comparative Analysis of Mainstream Discourses, Media Narratives and Representations of Islam in Britain and France Prior to 9/11” examines the construction of Islam, notably referring to the switch from exoticism before 9/11 to terrorism afterwards. 47 The article, however, does not discuss the construction of “British” and “French” but uses them as taken-for-granted cultural representations. Similarly, the article “The Construction of the Image of Immigrants and Ethnic Minorities in two Portuguese Daily Newspapers” discusses the way “their” image is fabricated and thus artificial but does not discuss the construction of the “Portuguese” identity. 48 Of course, focusing on minorities’ identities is highly relevant, but it could be beneficial to consider both majorities’ and minorities’ identities and cultures. Such an approach could help examine diversity among “us” rather than embodied only by “them”. Examining both majority and minority could enable researchers to go beyond this dichotomous opposition and not only look at differences but also cast light on shared cultural representations, practices or identities. Looking at differences and similarities, as well as how those are negotiated, can also help examine the way cultural meanings and identities are constructed in relation to one another. Overall, it would be a way to put all cultural practices and representations on an equal footing by explicitly defining them as constructed and contingent. This could in turn contribute to challenge taken-for-granted perceptions we have of ourselves as well as of others.

49 Anthony P. Browne, “Denying Race in the American and French Context,” Wadabagei 12 (2009): 83.

15 Findings also indicate that the concept of culture tends to be used in different ways depending on whose culture is examined. The “us” is often associated with nationality and presented as legitimate, neutral, acultural, aethnical and aracial while the “them” is often referred to in terms of religious or ethnic denominations. Oftentimes, culture is not directly problematized when the concepts of race and ethnicity are used. Eventually, this paints a picture where “we” seem to be acultural and unproblematic while “they” are described in terms of struggle, race, ethnicity or religious affiliations. The imbalance in such representations is problematic in that it reproduces stereotypical representations of minorities even though most studies intend to deconstruct them. Using alternatives to Western and Eurocentric approaches in media studies could help dismiss such a vicious circle. Enhancing geographical diversity as regards research location could also encourage study of various minority groups. Indeed, findings suggest that numerous studies are located in Europe, North America or Australia: parts of the world that embody the idea of “Western culture”. The lack of diversity in the location of research is a strong shortcoming of academic discourse, especially when it examines representation of minorities. Going through numerous articles dealing with ethnic or religious minorities living in the so-called Western world nourishes the idea that majority and dominant groups are white Europeans while struggling minorities are black, Asians or Muslims. Using a critical intercultural communication framework can discourage researchers from using or describing, even implicitly, certain groups or practices as acultural and neutral and others as only racial or ethnic. This issue has also been raised by scholars working on colorblind ideology. Browne, for instance, argues that in both the United States and France, being white is “the invisible norm against which all other cultural and racial groups are defined and subordinated”. 49 The notion of invisible norm raised by Browne is particularly relevant when it comes to seeing oneself as aracial or acultural and seeing others mostly through their skin color, religious affiliations or cultural practices. The way concepts of race and ethnicity can sometimes be used instead of the one of culture conveys the idea that they refer to different aspects. Nevertheless, race and ethnicity are forms of culture, as gender, nationality or social class can also be. Dismissing culture and using only race and ethnicity can be a drawback in that it contributes to presenting culture as unproblematic and natural, while race and ethnicity are sources of struggle. Using a critical intercultural communication framework is a way to be inclusive and critically tackle all aspects of culture. Bridging the gap between culture, race and ethnicity is also a way to bring together schools of thought (for instance, scholars from the United States and scholars from Europe) that have different stances on the concept of race itself. Examining critically the way race, ethnicity, social status, religious, sexual and gender identities are constructed and conveyed can thus enrich our understanding of culture. Generally speaking, using a critical approach to the concept of culture would help address problematic representations of minority/majority and us/them in academic discourse. Understanding culture as a construction that involves power relations and struggle contributes to include every individual, group and practice, since all aspects and members of societies are cultural. This therefore takes away the pervasive and implicit idea that some people or practices are neutral to some extent. Reflexivity is a central component in order to be able to detach oneself from ethnocentric representations and look at oneself, one’s culture, practices and values as cultural and therefore constructed and ideological. Focusing on cultural identity as constructed is also an asset in decreasing ethnocentrism or cultural bias in academic discourse. Encouraging researchers to be reflexive about their cultural backgrounds can help them problematize what they could otherwise take for granted about their own cultural identities and belongings. As Rorty points out, no one is ahistorical or acultural and therefore “everybody is ethnocentric when engaged in actual debate”. 50 The best way to overcome ethnocentric representations is to make them and the way they are constructed salient. Ethnocentrism in academic discourse is particularly problematic because research aims at being, if not entirely unbiased, at least critical towards its inherent subjectivity. Ethnocentrism as a form of bias is difficult to overcome if not addressed directly. Researchers should therefore aim at being critical towards their personal background as well as their philosophical, theoretical and methodological heritage. Cultural baggage has to be reflected upon at the individual level, that is, in the way personal choices affect the way researchers tackle a topic or analyze data, but also at the academic level, that is, the way they can be blind to the overall schools of thought to which they belong.

16 The concept of culture is regarded by many as ambiguous, difficult to conceptualize, and even non-operational by some scholars. In spite of its difficult reputation, culture remains a prominent object of study. Influences from critical theories and social constructionism make critical intercultural communication a relevant framework for examining representations and discursive constructions of culture. The premise that culture is constructed provides a solid ground to examine ways in which certain representations seem more powerful or natural than others. It also emphasizes the fact that we live in webs of cultural discourses – some invisible to us, depending on contexts – that are intertwined with other discourses. The main aim of using a critical intercultural communication framework is not to uncover what culture really is but to uncover what representations of culture come to appear real, and through which processes. Studies therefore primarily focus on the way we navigate these webs and make sense of them, the way they are constructed, interrelated and empowered. The main asset of this framework is its emphasis on problematizing culture, which reduces risks of taking it for granted. As such, critical intercultural communication also encourages researchers to be reflexive about their academic and cultural background. This can help one be aware of the extent to which one’s knowledge is situated, and therefore contributes to decreasing cultural bias in academic discourse. Generally, being aware of the representations we have of ourselves and others, as well as the reasons why these representations are constructed and conveyed, is central to developing understanding and tolerance towards others. This is especially relevant now that more and more people cross borders and that communication between cultures is faster, easier, and therefore increasingly common.

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Note de fin

1 Debra L. Merskin, Media, Minorities, and Meaning: A Critical Introduction (New York: Peter Lang Publishing, 2011).

2 Robert M. Entman, “Framing Bias: Media in the Distribution of Power,” Journal of Communication 57, (2007).

3 Sari Pietikäinen and Helen Kelly-Holmes, “The Dangers of Normativity – The Case of Minority Language Media,” in Dangerous Multilingualism: Northern Perspectives on Order, Purity And Normality , ed. Jan Blommaert et al . (Houndmills, Basingstoke: Palgrave Macmillan, 2012), 194–204.

4 Isabelle Rigoni, “Intersectionality and Mediated Cultural Production in A Globalized Post-Colonial World,” Ethnic and Racial Studies 35 (2012).

5 Robert Brightman, “Forget Culture: Replacement, Transcendence, Relexification,” Cultural Anthropology 10, (1995).

6 William H. Sewell Jr, “The Concept(s) of Culture,” in Practicing History: New Directions in Historical Writing after the Linguistic Turn , ed. Gabrielle M. Spiegel (New York: Routledge, 2005), 76–95.

7 Ingrid Piller, Intercultural Communication: A Critical Introduction (Edinburgh: Edinburgh University Press, 2011), 15.

9 Fred Dervin, “Approches dialogiques et énonciatives de l’interculturel : Pour une didactique des langues et de l’identité mouvante des sujets,” Synergies Roumanie 4 (2009): 166–167.

10 Fred Dervin, “A Plea for Change in Research on Intercultural Discourses: A “Liquid” Approach to the Study of the Acculturation of Chinese Students,” Journal of Multicultural Discourses 6 (March 2011): 38.

11 Sylvie Poirier, “La (dé)politisation de la culture? Réflexions sur un concept pluriel, ” Anthropologie et sociétés 28 (2004): 10 – 13.

12 Ryuko Kubota, “Critical Approaches to Intercultural Discourse and Communication,” in The Handbook of Intercultural Discourse and Communication , ed. Christina Bratt Paulston et al . (Malden, USA: John Wiley & Sons, 2012), 95.

13 Stuart Hall, “Introduction,” in Representation: Cultural Representations and Signifying Practices , ed. Stuart Hall (London: Sage Publications, 1997), 3.

15 William A. Gamson and Andre Modigliani, “Media discourse and Public Opinion on Nuclear Power: A Constructionist Approach,” American Journal of Sociology 95 (1989): 5.

16 Nancy K. Rivenburgh, “Media Framing of Complex Issues: The Case of Endangered Languages,” Public Understanding of Science 22 (2011): 706.

17 Ulrika Olausson, “Global warming – Global Responsibility? Media Frames of Collective Action and Scientific Certainty,” Public Understanding of Science 18 (2009): 423.

18 Marianne Jørgensen and Louise J. Phillips, Discourse Analysis as Theory and Method (London: Sage Publications, 2002), 175–177.

20 Keith V. Erickson, Cathy A. Fleuriet and Lawrence A. Hosman, “Prolific Publishing: Professional and Administrative Concerns,” The Southern Communication Journal 58 (Summer 1993): 328–329.

21 Michael W. Kramer, Jon A. Hess and Loren D. Reid, “Trends in Communication Scholarship: An Analysis of Four Representative NCA and ICA Journals over the Last 70 Years,” The Review of Communication 7 (July 2007): 229–230.

23 Maggie MacLure, Discourses in Educational and Social Research ( Buckingham: Open University Press, 2003), 175.

24 Ronald D. Gordon, “Beyond the Failures of Western Communication Theory,” Journal of Multicultural Discourse 2 (2007).

25 Molefi Kete Asante, “The Ideological Significance of Afrocentricity in Intercultural Communication,” Journal of Black Studies 14 (1983).

26 Yoshitaka Miike, “Non-Western Theory in Western research? An Asiacentric Agenda for Asian Communication Studies,” The Review of Communication 6, (2006).

27 Yoshitaka Miike, “An Asiacentric Reflection on Eurocentric Bias in Communication Theory,” Communication Monographs 74 (2007).

29 Shi-Xu, “Reconstructing Eastern Paradigms of Discourse Studies ,” Journal of Multicultural Discourses 4 (2009): 33.

30 Hui-Ching Chang, Rich Holt and Lina Luo, “Representing East Asians in Intercultural Communication Textbooks: A Select Review,” The Review of Communication 6 (2006): 325–326.

31 Molefi Kete Asante, Afrocentricity: The Theory of Social Change (Chicago: African American Images, 2003), 61.

32 Ella Shohat and Robert Stam, Unthinking Eurocentrism: Multiculturalism and the Media (London: Routledge, 1994); James Curran and Myung-Jin Park, De-westernizing Media Studies (London: Routledge, 2000).

33 Eric Kit-Wai Ma, “Rethinking Media Studies: The Case of China,” in De-westernizing Media Studies , ed. James Curran et al . (London: Routledge, 1994), 32.

34 See for example Gordon, “Beyond the Failures of Western Communication Theory,” and Miike, “An Asiacentric Reflection on Eurocentric Bias in Communication Theory”.

35 Annelies Verdoolaege, “Media representations of the South African Truth and Reconciliation Commission and their Commitment to Reconciliation,” Journal of African Cultural Studies 17 (2005).

36 Jawad Syed, “The Representation of Cultural Diversity in Urdu-Language Newspapers in Pakistan: A Study Of Jang And Nawaiwaqt,” Journal of South Asian Studies 31 (2008).

37 Yasmin Jiwani, “War Talk Engendering Terror: Race, Gender and Representation in Canadian Print Media,” International Journal of Media & Cultural Politics 1 (2005).

38 Fabienne Darling-Wolf, “Sites of Attractiveness: Japanese Women and Westernized Representations of Feminine Beauty,” Critical Studies in Media Communication 21 (2004).

39 Maria Andrea Dos Santos Soares, “Look, Blackness in Brazil!: Disrupting the Grotesquerie of Racial Representation in Brazilian Visual Culture,” Cultural Dynamics 24 (2012).

40 Anna Bredström, “Gendered Racism and the Production Of Cultural Difference: Media Representations and Identity Work among ‘Immigrant Youth’ In Contemporary Sweden,” Nora: Nordic Journal of Women’s Studies 11 (2003).

41 Shanara Rose Reid-Brinkley, “Ghetto Kids Gone Good: Race, Representation, and Authority in the Scripting of Inner-City Youths in the Urban Debate League,” Argumentation & Advocacy 49 (2012).

44 Rona T. Halualani, S. Lily Mendoza and Jolanta A. Drzewiecka, “‘Critical’” Junctures in Intercultural Communication Studies: A Review,” The Review of Communication 9 (January 2009): 24.

47 Malcom D. Brown, “Comparative Analysis of Mainstream Discourses, Media Narratives and Representations of Islam in Britain and France Prior to 9/11,” Journal of Muslim Minority Affairs 26 (2006).

48 Margarida Carvalho, “The Construction of the Image of Immigrants and Ethnic Minorities in Two Portuguese Daily Newspapers,” Portuguese Journal of Social Science 9 (2010).

Richard Rorty, “Solidarity or Objectivity,” in Knowledge and Inquiry. Readings in Epistemology , ed. K. Brad Wray (Peterborough, ON: Broadview Press, 2002), 432.

Pour citer cet article

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Mélodine Sommier , «  The Concept of Culture in Media Studies: A Critical Review of Academic Literature  » ,  InMedia [En ligne], 5 | 2014, mis en ligne le 17 octobre 2014 , consulté le 09 novembre 2023 . URL  : http://journals.openedition.org/inmedia/768 ; DOI  : https://doi.org/10.4000/inmedia.768

Mélodine Sommier

Mélodine Sommier is a doctoral student in intercultural communication at the University of Jyväskylä in Finland. She has particular interests in migration and acculturation issues as well as discourses of culture in the media.

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Le texte seul est utilisable sous licence CC BY-NC 4.0 . Les autres éléments (illustrations, fichiers annexes importés) sont « Tous droits réservés », sauf mention contraire.

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• Microbiology , Science

Culture Media: Classification, Types, and Relevance

Anjali singh, what is culture media.

Culture media are mediums that provide essential nutrients and minerals to support the growth of microorganisms in the laboratory.

Microorganisms have varying nature, characteristics, habitat, and even nutritional requirements, thus it is impossible to culture them with one type of culture media. However, there are also microorganisms that can’t grow on a culture media at all in any condition – these are called obligate parasites. [1]

Culturing microorganisms is essential for diagnosing infectious diseases, obtaining antigens, developing serological assays for vaccines, genetic studies, and identification of microbial species. [1]

Furthermore, it’s also essential for isolating pure cultures, storing culture stock, studying biochemical reactions, testing microbial contamination, checking antimicrobial agents and preservatives effect, testing viable count, and testing antibiotic sensitivity. [2]

This article will focus on the composition, classification, and types of culture media used in microbiology labs to study a spectrum of microbial forms.

Classification and Types of Culture Media

Growing microorganisms in the lab involve mimicking the organisms’ natural habitat or environment, and this is possible in the laboratory by formulating culture media that meets their requirements. Therefore, many culture media were developed by scientists according to the microbial species to be cultured.

The basic media contains a source of carbon & energy, nitrogen source, growth factors, and some trace elements. [1] Some commonly used media components include peptone, agar, water, casein hydrolysate, malt extract, meat extract, and yeast extract. In addition, the pH of the medium should be set accordingly. [3]

However, some additional components or nutrients are added to the media when growing specific microorganisms.

Culture media can be classified in three ways: based on their consistency, nutritional component, and applications. [1]

A. Classification of culture media based on consistency

• Solid media: In these media, the agar which is an unbranched long chain of polysaccharides is added in the concentration of 1.5-2.0%. Most commonly, 1.3% agar is used to prepare solid media in labs. The agar-containing media solidifies at 37 ºC. [1] Sometimes, in the place of agar, some other inert solidifying agents are used, such as gellan gum. Solid media are used to grow microorganisms in their full physical form, prepare bacterial pure cultures, or isolate bacteria to study colony characteristics. [1] The bacterial growth on solid media varies in appearance as mucoid, round, smooth, rough, filamentous, irregular, and punctiform. The media is not hydrolyzed by microorganisms and is free from growth-inhibiting substances. [3] Examples of solid media are blood agar, nutrient agar, McConkey agar, and chocolate agar.
• Semisolid media: This media has 0.2-0.5% agar concentration, and due to the reduced agar concentration, it appears as a soft, jelly-like substance. It’s mainly used to study the motility of microorganisms, distinguish between motile and non-motile bacterial strains (through U-tube and Cragie’s tube), and cultivate microaerophilic bacteria – bacteria on this media appear as a thick line. Examples of semi-solid media are: Hugh and Leifson’s oxidation fermentation medium, Stuart’s and Amies media, and Mannitol motility media. [1]
• Liquid media: These media do not contain any traces of solidifying agents, such as agar or gelatin, and large growth of bacterial colonies can be observed in the media. Liquid media are also called broths, they allow for uniform and turbid growth of bacterial strains when incubated at 37ºC for 24hrs. The media is used for the profuse growth of microorganisms and fermentation studies. Examples include Tryptic soy broth, phenol red carbohydrate broth, MR-VP broth, and nutrient broth.

Other than these, there are also biphasic media, which consist of both solid and liquid media. And sometimes in the place of agar, egg yolk and serum are added to the media as a solidifying agent. [3]  Learn more on how to make agar plates here.

While naturally, these substances are liquid, they are solidified by using heat, and the prepared media is sterilized using the inspissation technique. Examples are Lowenstein Jensen medium and Dorset egg medium, which contain egg yolk, and Loeffler’s serum slope, which contain serum. [3]

B. Classification based on the nutritional component

• Simple media: It’s a general-purpose media that supports the growth of non-fastidious microbes, and it is primarily used for the isolation of microorganisms. Examples are nutrient broth, peptone water, and nutrient agar.
• Complex media: These are media containing nutrients in unknown quantities that are added to bring about a particular characteristic of a microbial strain. Examples are tryptic soy broth, blood agar, and nutrient broth.
• Synthetic media: Synthetic media is a type of chemically defined media and is produced from pure chemical substances. A defined media refers to a medium having a known concentration of ingredients, like sugar (glucose or glycerol) and nitrogen source (such as ammonium salt or nitrate as inorganic nitrogen). It is generally used in scientific research, and an example is Czapek Dox Medium. [1]

C. Classification of culture media based on application/chemical composition

They are generally used to isolate microorganisms in labs or in sub-culturing processes. Examples are nutrient broth, nutrient agar, and peptone water.

• Enriched media: This media is prepared by adding additional substances like blood, serum, or egg yolk in the basal medium. It’s used to grow fastidious microorganisms as they require additional nutrients and growth-promoting substances. Examples are chocolate agar, blood agar, and Loeffler’s serum slope. Chocolate media is used to grow N. gonorrhea while blood agar (which is prepared by adding 5-10% blood by volume to a blood agar base) is used to identify hemolytic bacteria. [2]

Below is a list of common selective media and the bacteria they’re used to culture: [2]

• Enrichment media: It’s a liquid medium, used to increase the relative concentration of certain microbes before culturing them on a solid medium plate. It’s used as a broth medium and inhibits the growth of commensal species of microorganisms (those who live in close association with each other) in the clinical specimen. It’s also used in isolating fecal and soil microorganisms. Examples are selenite F broth which is used to isolate Salmonella typhi from a fecal sample, tetrathionate broth, and alkaline peptone water. [1]
• Blood agar: In blood agar, three types of blood cell lysis or hemolysis are observed: alpha, beta, and gamma hemolysis. [5] It allows the growth of many microorganisms, however, their ability to lyse blood cells differs, and this helps to distinguish the bacterial colonies. For example, S. pyogenes completely lyse blood cells (beta hemolysis), thus causing total clearing of the media around its colonies. S. pneumoniae partially lyse red blood cells, resulting in a greenish-colored medium, while gamma hemolytic microorganisms like Enterococcus faecalis, Staphylococcus saprophyticus, and Staphylococcus epidermidis , can’t lyse red blood cells, thus causing no color change in the medium. [6]
• Mannitol salts agar: The fermentation of mannitol by Staphylococcus aureus causes the media to change to yellow, however, coagulase-negative staphylococci that can’t cause fermentation to appear in pink. [7]
• MacConkey agar: It differentiates the gram-negative bacteria based on their lactose metabolism. The lactose fermenting bacteria, such as Escherichia coli, Klebsiella spp, Citrobacter, and Enterobacter forms pink-red colonies, while lactose non-fermenters, like Salmonella, Shigella, Proteus, Providencia, Pseudomonas, and Morganella form pale or colorless colonies. [8]
• Thiosulfate citrate bile salts sucrose (TCBS) agar: The media contain sucrose, which is utilized by ferment microbes and helps to distinguish them from non-ferment microorganisms. Based on this characteristic, different colored bacterial colonies are formed on the media that help to identify and distinguish them from each other. For example, V. cholerae ferment the sucrose and form slightly flattened yellow colonies having opaque centers and translucent peripheries. Whereas, V. parahaemolyticus can’t ferment the sucrose and forms green to blue-green colonies. [9]
• Sach’s buffered glycerol saline : It’s used to transport feces from patients suspected to be suffering from bacillary dysentery.
• Cary Blair transport and Venkatraman Ramakrishnan media: Fecal samples collected from suspected cholera patients are transported using these media.
• Pike’s medium: A throat specimen containing Streptococci is transported using this medium. [2]
• Anaerobic media: This media is for anaerobic bacteria which require low oxygen levels, extra nutrients, and reduced oxidation-reduction potential. It is supplemented with hemin and vitamin K nutrients and oxygen is removed by boiling it in a water bath and sealing it with paraffin film. [2] Examples are: Thioglycollate broth and Robertson Cooked Meat (RCM) medium which is commonly used to grow Clostridium spp. [2]
• Assay media: It’s used for amino acids, vitamins, and antibiotics assays. For example, antibiotic assay media is used to determine the antibiotic potency of microorganisms.
• Storage media: It’s used to store microorganisms for a longer period, examples are chalk cooked meat broth and egg saline medium. [2]

Culture media is a source of nutrients and growth factors required for the growth of microorganisms and even plants in laboratory conditions. Every organism has different nutritional requirements based on its habitat or living conditions. Therefore, a single formulation of culture media can’t be used to grow all organisms in labs.

Many types of culture media have been developed by scientists to grow selective or desired microorganisms. These are classified based on their nutrient composition, consistency, and application or use in life science laboratories.

Culture media serve several purposes in labs like isolating specific strains of microorganisms, identifying disease-causing pathogens, preparing pure culture of a microbial species, distinguishing bacterial species, and studying their responses to certain antibiotics.

Thus, before deciding which culture media to use, it is critical to determine the purpose of your study and in some cases the type of microorganism you want to study. This narrows down your choices and helps you to choose which media is best for your experiment, without wasting your time and effort.

References:

• Tankeshwar Acharya (2021). Bacterial Culture Media: Classification, Types, Uses. Retrieved from https://microbeonline.com/types-of-bacteriological-culture-medium/ .
• Fatima Aiman (2022). Microbial Culture Media- Definition, Types, Examples, Uses. Retrieved from https://microbenotes.com/types-of-culture-media/#application-of-culture-media .
• Rao Sridhar. Bacterial Culture Media. Retrieved from https://www.microrao.com/micronotes/pg/culture_media.pdf .
• Aryal Sagar (2022). Salmonella Shigella (SS) Agar- Composition, Principle, Preparation, Results, Uses. Retrieved from https://microbenotes.com/salmonella-shigella-ss-agar/ .
• Tankeshwar Acharya (2021). Blood Agar and Types of Hemolysis. Retrieved from http://microbeonline.com/blood-agar-composition-preparation-uses-and-types-of-hemolysis/ .

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