Characterisation of the microbial population at different stages of Kefir production and Kefir grain mass cultivation

Kefir is a fermented milk that is produced by adding Kefir grains, consisting of bacteria and yeasts, to milk. The aim of this study was to determine the microbial population at different stages of traditional Kefir production and Kefir grain mass cultivation. Seven different selective growth media, morphological and biochemical characteristics were used for the isolation and identification of the microbes. The microbial numbers during Kefir production varied between 4.6×103 and 2.6×108. A Zygosaccharomyces sp. was isolated from traditional Kefir grains and after the culturing conditions applied during the mass cultivation Candida lambica and C. krusei were present. Although these two species are present in other fermented milks, this study is the first to report their presence in Kefir. Species of Leuconostoc, Lactococcus, Lactobacillus and Cryptococcus were isolated from traditional grains. Lactobacillus plantarum was present in the mass cultivated grains, but not in the traditional Kefir grains.