Multi-omics characterization of microbial, nutritional and flavor features and their correlations in traditional fermented yak milk from the Nagqu region of Tibet

Traditional fermented yak milk has important nutritional and cultural value for Nagqu region of Tibet. In this study, we performed multi-omics characterization of microbial, nutritional and flavor features and their correlations in traditional fermented yak milk from this region. Metagenomics revealed that Lactobacillus delbrueckii and Streptococcus thermophilus were dominant bacteria in fermented yak milk. Untargeted metabolomics identified 1136 non-volatile metabolites, mainly fatty acyls and carbohydrates. Among the 59 volatile metabolites discovered, esters like ethyl butyrate and ethyl decanoate were the primary flavor contributors. Notably, significant differences in microorganism and non-volatile metabolites occurred at the county level, but not village. Correlation analysis showed that lactic acid bacteria positively correlated with carbohydrate and organic acid, while yeast contributed to the formation of phenolic and ester, and Lactobacillus delbrueckii and Kluyveromyces marxianus may be the core microorganism that influences nutrition and flavor. This experiment provides valuable insights into the quality characteristics and its formation mechanism of fermented yak milk in Nagqu region.