Lactic Acid Bacteria and Yeasts from Milk Kefir Grains: Isolation, Characterization, Screening, and Identification

Lactic acid bacteria and yeast are abundant in kefir grains. Six natural kefir grains were used in this research to isolate and purify 64 strains of yeast and 108 strains of lactic acid bacteria. A total of three lactic acid bacteria and one yeast strain (Lactococcus lactis 2C6, Lactobacillus helveticus 6171, Lactobacillus plantarum 4M2 and Saccharomyces cerevisiae 6Y6) were examined for their ability to protein hydrolysis, water holding capacity, alcohol production, acid and bile salt tolerance and identified by 16S rDNA. The proteolytic ability, alcohol generation, and acid and bile salt tolerance of 4M2 and 6Y6 were excellent. Lyophilization was used to create bacterial powder, which laid the foundation for the subsequent development of direct-vat-set (DVS) kefir starter.