Peptones and Extracts for Culture Media: The Properties that Matter
A variety of peptones and extracts are available from Merck for producing culture media to be used in a wide range of industrial microbiology applications.
Peptones are a mixture of water soluble polypeptides, peptides, amino acids and other substances remaining after the digestion of protein material. The quality of the peptones is determined by the quality of the selected raw materials, their storage conditions and digestion parameters. Raw materials must stored in a way that prevents the growth of spoilage organisms.
Peptones are used in a wide range of microbiological applications. Applications may require different peptones: A peptone that is suitable for optimal growth of one organism may not be satisfactory for other organisms or for the production of a compound or cell culture. A range of visual, physical, biochemical (USP) and composition properties characterize peptones. However, if the composition, appearance, biochemical, chemical and physical test parameters are satisfactory, the peptone may still be unsuitable for use in culture media if biological tests yield abnormal results. For selecting a cell culture or optimizing its performance, or for fermentation applications it is often necessary to test various peptones at different concentrations.
An extract is an infusion, i.e. the water soluble fraction obtained by soaking a substrate in water for a period of time, followed by filtration to clear the solution. The substrates are often digested by a weak proteolysis with pancreatin (of porcine origin) before being filtered and concentrated. For high-yield fermentation, many media need to be supplemented with extracts.