Diversity Analysis Of Lactic Acid Bacteria In Traditional Yak Milk Products In Tibet

In this study, thirty nine samples of traditional fermented yak milk products and raw milk which came from local pepple were collected from two different areas of seven counties in Lasa, Tibet, China. The lactic acid bacteria (LAB) resources that were belonged to yak milk products were isolated, identified and stored based on traditional pure culture method combined with16S rDNA sequencing analysis and uncultured methods (Denaturing Gradient Gel Electrophoresis), meanwhile, the microbiological biodiversity of yak milk products were comprehensively evaluated by the culture method compared with uncultured.The viable counts of LAB in yak milk products were determined by dilution method of plate counting, that were ranged from6.76lg CFU/mL to9.37lg CFU/mL, besides the results of few samples were lower than107CFU/mL, most of them were up to8.00lg CFU/mL; LAB from these samples were separated and purified by LAB selective medium (MRS and M17) combined with morphological observation, gram faerbung and catalase test,213strains of LAB isolates were preliminarily isolated.213isolates were identified to species levels by16S rDNA sequences analysis. The results showed that all the isolates were classified into six genera, twenty-two species and/or subspecies, Lactobacilli were the dominating species by55.40%(118strains) of total; Leuconostoc run second with74strains of total (34.74%);5strains of Streptococci (2.35%);8strains of Lactococci (3.6%);4strains of Enterococci (1.88%) and4strains of Weissella (1.88%). According to biodiversity analysis on LAB from yak milk products, Lactobacilli delbrueckii subsp. bulgaricus (60strains,28.17%of total) and Leuconostoc lactis (35strains,16.43%) could be recognised as the dominanting LAB species in yak milk products in Tibet.The16S rDNA sequences of213identified LAB strains were uploaded to GenBank database with the accession numbers as KF149649-KF149861。Microbial diversity in seven representative yak milk samples from Tibet were analyzed using metagenomic method PCR-DGGE. The result showed that4kinds of LAB species (L.helveticus, L.delbrueckii subsp. bulgaricus, Lac.lactis, L.helveticus and S.thermophiles) and Enterobacteriaceae were exised in these sampls.Microbial diversity of the yak milk products were studied by the pure culture method combined with metagenomics technology, the result showed that the microorganisms in yak milk products were diverse, LAB could be considered as the major genera which involved in fermentation, among which Lactobacillus was the dominating species. The conclusion which L. bulgaricus was the dominating species by pure cluture method was confirmed with uncultured technology.