Microorganisms of Kefir

Kefir can only be made from kefir grains and mother cultures prepared from grains.

The grains contain a relatively stable and specific balance of microorganisms which exist in a complex symbiotic relationship. Kefir grains looks like cauliflowers or small coral reefs since lactic acid bacteria and yeast are curdled with polysaccharide with viscous property (Figure). Kefir grains continue to grow with forming a lump of its diameter of 3 to 30mm when fresh milk is regularly supplied.

Kefir grains are clusters of microorganisms held together by a matrix of polysaccharides. A various species of microorganisms have been isolated and identified from kefir grains. Such species are among genus groups; Lactobacilli, Streptococci, Lactococci, Leuconostoc, Acetobacter and Yeasts. The bacteria and yeast component share a symbiotic relationship. They share their by-products as an energy and growth-stimulating source and work together to produce health benefit products.

The grain is usually composed of a complex of approximately 13% protein, 24% polysaccharide, and microorganisms by dry weight basis. The principal polysaccharide is a water-soluble substance known as kefiran which produced from homofermentative Lactobacillus species such as L. kefiranofaciens and L. kefir. With an electron microscope, a lump of lactic acid bacteria and yeast can be observed with polysaccharide in a kefir grain (Figure). The key lactic acid bacteria include Lactobacillus genus L. brevis, L. kefir, L. paracasei, L. plantarum, L. acidophilus, L. delbrueckii subsp. bulgaricus, L. kefiranofaciens, and L. lactis as well as Leuconostoc genus L. mesenteroides subsp. mesenteroides, L. mesenteroides subsp.dextranicum, L. mesenteroides subsp. cremoris, and L. lactis. Yeast is another type of microorganisms contained in Kefir. During a fermentation process, yeasts produce useful materials such as amino acid, nucleic acid, and peptide. It is known that in Kefir, there are such kinds of yeasts as Saccharomyces kefir, Torula kefir, Candida kefir, Kluyveromyces marxianus var. marxianus.
 

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