Millipore Sigma Vibrant Logo
Attention: We have moved. Merck Millipore products are no longer available for purchase on More

Biological Raw Materials


Peptones, Extracts and Agar-Agar

Biological Raw Materials for Culture Media

Biological raw materials (peptones, extracts, agar-agar), core ingredients of many culture media, are available from Merck in a considerable variety of products to meet a wide range of industrial microbiology applications.

All our peptones, agar-agar and extracts enable optimal performance due to our strict quality control and assurance standards. The format in which Merck manufactures most of these raw materials is as dehydrated granules. Working with granulated raw materials produces less dust contamination of the laboratory environment. The granules dissolve quickly to ensure optimal flow properties.

Dehydrated Raw Materials

Dehydrated Raw Materials

All Products

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.

Agar-Agar for Culture Media: The Properties that Matter

Agar-agar for producing solid agar-based culture media to be used in a wide range of industrial microbiology applications is available in a variety of properties from Merck.

Agar-agar is the cell wall polysaccharide that structures the cellular cohesion of seaweed. The red algae genera containing agar-agar include Gelidium, Gracilaria, Petrocladia and Anpheltia. The best quality agar-agar for bacteriological use is obtained from Gelidium sesquipedale. Merck’s agar-agars are manufactured from this species

Agar-agar for bacteriological purposes vary in gel strength, mineral and acid content. Ultra purification produces agar-agar with very low mineral and nitrogen content. The ideal agar-agar for microbiological use is free of impurities, heat-resistant bacteria and any substances which might inhibit the growth of microorganisms. It is generally clear and free of pigments. However, a “floc” may appear after the clarification process due to remaining calcium, magnesium and phosphate. Bacteriological agar-agar should have only a physical function. It should not be a source of nutrients or chemically active.

Agar-agar is commonly characterized by its content of moisture, sulphated ash, toxic heavy metals, calcium, magnesium as well as its gel strength and solidification point. Gel strength, setting temperature and clarity are key criteria for the selection of agar-agar.