Abstract: 【Objective】To screen dominating microbial species isolated from Tibetan Kefir and develop pure-culture starter. 【Method】PCR-DGGE and traditional culture-depending methods were combined to examine the microbial community of Tibetan kefir. 【Result】 Four bands in the DGGE profiles of total bacterial DNA of Tibetan kefir were not recovered by cultivation. Conversely, two bacterial species did not exhibit bands in DGGE fingerprints of total bacterial DNA of Tibetan kefir. 150 strains isolated were screened and grouped by PCR-DGGE, eight lactic acid bacteria and five yeasts were obtained. Comparison of 16S rDNA (bacteria) and 26S rDNA (yeast) partial sequence similarity revealed that the dominating microbial species of Tibetan kefir were Leuconostoc mesenteroides, Lactococcus lactis, Lactobacillus kefiri, Lactobacillus casei and Kluyveromyces marxianus, Saccharomyces unisporus, Saccharomyces cerevisiae and Candida humilis were dominating during last fermentation. 【Conclusion】 An effective microbial screening technology based on molecular microbiology was established in this study, providing theoretical basis and rich microbial resources for the development of Tibetan Kefir pure-culture starter.

Key words: Tibetan kefir, PCR-DGGE, Microbial diversity, Dominating microbial species, Screen