Overview of Peptones in Culture Media

Peptones (protein hydrolysates) are widely used as a protein source in culture media (Table 1). They are soluble mixtures of polypeptides and amino acids that are formed from the hydrolysis of animal and plant proteins. Peptones are also rich in water-soluble minerals and micronutrients derived from the original protein source and are, therefore, a complex mixture of compounds that provide critical nutritional support for cell growth and proliferation, microbial fermentation, and production of recombinant proteins. Typical protein sources for peptones include meat, milk, soybean, yeast, and gelatin.

Teknova offers peptones in different formats: dry, preformulated in culture plates (Table 2), or preformulated in culture media (Table 3). We also offer custom media and plate formulations for research use or as GMP (good manufacturing practices) products.

Peptone Production: Protein Hydrolysis

Protein hydrolysis is accomplished using either acid hydrolysis, enzymatic hydrolysis, microbial hydrolysis, or autolysis.

Acid hydrolysis is a harsh process that is typically performed at high temperature. These harsh conditions hydrolyze all peptide bonds, destroying some amino acids. Vitamins are also destroyed.

Enzymatic and microbial hydrolysis are gentler than acid hydrolysis and result in a mixture of amino acids and polypeptides of varying lengths. The most widely used enzymes for hydrolysis include trypsin and pepsin from animal sources and papain from papaya. Enzymatic hydrolysis is typically used for producing peptones from animal sources such as meat and dairy. Microbial hydrolysis is performed using proteases from bacteria, algae, and fungi.

Yeast extracts are generated by autolysis, whereby enzymes within the yeast cells hydrolyze their own proteins.

Which Peptone is Right for Your Application?

In addition to the more common peptones derived from meat, casein (milk protein), and soy, we offer peptone products from a wide range of animal and non-animal sources. These peptones provide nutrients to sustain the growth of most organisms. The nitrogen and amino acid content of peptones differ slightly depending on the source.

Meat- and casein-based peptones are of bovine origin and are suitable for applications that have no or limited animal-origin requirements. All our peptones of animal origin are prepared from animals that are suitable for human consumption. This ensures that the material is free from bovine or transmissible spongiform encephalopathies (BSE/TSE).

Meat peptones are obtained from animal tissues, including muscle, bone, skin, and pancreas. Various proteases may be used for enzymatic hydrolysis of these tissues. The most commonly used proteases are trypsin (from pancreas) and pepsin (from swine or bovine stomach).

Tryptone is produced by enzymatic hydrolysis of casein using pancreatic enzymes. Tryptone is widely used in the pharmaceutical, diagnostics, and veterinary industries.

Soy peptone (Soytone) is produced by enzymatic hydrolysis of defatted soybean meal/flour using either papain (from papaya) or pancreatic enzymes. Soytone has a naturally high vitamin and carbohydrate content, making it suitable for the growth and maintenance of a wide variety of organisms, including those that are difficult to grow.

Table 1. Uses of common peptones.

Meat Peptone Tryptone Soytone
Source Animal (bovine tissue) Casein (milk protein) Defatted soybean meal
Digest Type Enzymatic Pancreatic Pancreatic or papain (animal-free)
Uses Growth and maintenance of fastidious and non-fastidious microorganisms Production of antibiotics, toxins, enzymes, and other biological products Growth and maintenance of various microorganisms, including bacteria and fungi

Common Culture Products Preformulated with Peptones

Agar plates are often used to grow and isolate individual colonies of microorganisms, which can be used for identification, screening (e.g., specific plasmid constructs, protein expression), or short-term storage. Varying the growth media in the agar plate allows different types of microorganisms to grow (Table 2). (Learn more about the history of agar as a microbiology tool.)

Liquid broth media support high density growth in suspension for a variety of purposes, including colony screening, plasmid production, protein production, and creation of frozen stocks for long-term storage.

Additional information about types of culture media, how to choose bacterial broth culture media, and LB media are available on our website.

Table 2. Example agar plates containing peptones.

Plate Type Meat Peptone Tryptone Soytone Usage (Example Organism)
2X YT Agar Plates Recombinant E. coli
EMB Agar Plates Gram negative bacilli
LB Agar Plates Recombinant E. coli
LB Agar Plates with Animal-Free Soytone* Bacteria
MacConkey Agar Plates Differentiation of lactose and non-lactose fermenting nonfastidious gram-negative bacteria (particularly, from the Enterobacteriaceae family)
Nematode Growth Media Plates C. elegans and other nematodes
Nutrient Agar Plates Nonfastidious bacteria
Sabouraud Dextrose Agar Plates Yeast, molds (including dermatophytes), and aciduric bacteria
Tryptic Soy Agar Plates Nonfastidious and moderately fastidious bacteria

* For applications where the use of animal products presents a safety hazard and a source of unwanted contamination. Lot-to-lot consistency is also greater with animal component-free (ACF) plates.

Table 3. Example liquid, broth media containing peptones.

Broth Type Meat Peptone Tryptone Soytone Usage (Example Organism)
2X YT Broth Recombinant E. coli
814 GC Medium Fastidious bacteria (e.g., Neisseria, Haemophilus, and Helicobacter spp.)
LB Broth Recombinant E. coli
LB Broth with Animal-Free Soytone* Recombinant E. coli
LB Lennox Broth Recombinant E. coli
Super Broth Recombinant E. coli for high plasmid yields
Terrific Broth Complete Recombinant E. coli for high density growth for plasmid production
Terrific Broth Complete with Animal-Free Soytone* Recombinant E. coli for high density growth for plasmid production
Tryptic Soy Broth, Animal-Free* Bacteria that have high nutritional requirements
YEP Broth Schizosaccharomyces pombe (vegetative growth)
YPD Broth Saccharomyces cerevisiae

* For applications where the use of animal products presents a safety hazard and a source of unwanted contamination. Lot-to-lot consistency is also greater with animal component-free (ACF) plates.

For our full range of standard media formulations, refer to the relevant listings in the Products menu. You can also search for specific products if you know what you need.

To enquire about custom or GMP formulations or for assistance with choosing the appropriate media for your application, use our website chat or contact us.