Study On Microbial Diversity Of Tibetan Traditional Fermented Yak Milk By High-Throughput Sequencing

Naturally fermented yak milk (NFYM) is a traditional Tibetan fermented product, which contains a rich microbial community. It was used high-throughput 454 pyrosequencing to investigate the bacterial and fungal community diversity of 16 NFYM samples from Geda and Ningzhong villages in Tibet in this thesis. A total of 112,173 high quality bacterial 16S rRNA gene sequences and 90,980 high quality fungal ITS gene reads were obtained from the NFYM samples. All of Sequences were identified to eleven bacterial and five fungal phyla by genes BLAST analysis, among which Firmicutes and Ascomycota were regarded as predominated organisms. At genus level, Lactobacillus and Saccharomyces were regared as dominated bacteria and fungi micoflora, respectively. There was no significant difference in the structure of bacterial and fungal microbiota between samples from two regions based on weighted and unweighted UniFrac Principal coordinate analysis. However, multivariate analysis of variance (MANOVA) based on unweighted UniFrac distances showed there was significant difference (P< 0.05) existed in the bacterial and fungal community population between the NFYM samples collected from the two villages. 49 key OTUs (operational taxonomic units) were identified after the RDA (redundancy analysis). Among them,7 OTUs (Acinetobacter, unidentified Bacteroidetes, Lactobacillus, unidentified Proteobacteria, Streptococcus, Pantoea and unidentified Firmicutes) were enriched in Geda village samples, while 42 OTUs (mainly Massilia, Propionibacterium, Lactococcus, Leuconostoc and Enterococcus) were enriched in Ningzhong village. It was shown that microbiota composition of fermented yak milk in Tibetan maybe related with their geographic regions. The present work could provid basis for the quality improvement in Tibetan NFYM in future.