Metagenomic insights into bacterial communities and functional genes associated with texture characteristics of Kazakh artisanal fermented milk Ayran in Xinjiang, China

The complex microflora of traditional fermented milk is crucial to milk coagulation mainly through acid and protease production; however, it is still unclear which microbes and proteases significantly influence the texture of Ayran, a Kazakh artisanal fermented milk in Xinjiang, China. In this study, fifty-nine samples of Ayran were collected and investigated on texture properties. Finally, six Ayran samples with different texture features were screened out, and the taxonomic and functional attributes of their microbiota were characterized by meta-genomics. The results showed that the hardness of the fermented milk in Yili Kazakh Autonomous Prefecture was significantly higher than that in other pasture areas. Lactobacillus and Lactococcus were the core genera that affected the coagulation quality of milk. Furthermore, we found that the proline iminopeptidase pip (EC 3.4.11.5) gene of Lactobacillus helveticus and Limosilactobacillus fermentum and the dipeptidase E pepE (EC 3.4.13.21) gene of Lactococcus lactis were most associated with the coagulation quality of fermented milk. Furthermore, positive correlations were observed among the hardness of fermented milk, the activity of the proteases, and the cor-responding functional gene expressions.

Automated summary

In this study, the texture properties of Ayran, a Kazakh artisanal fermented milk in Xinjiang, China, were investigated. Six Ayran samples with different texture features were characterized, and their microbiota were analyzed. Lactobacillus and Lactococcus were identified as the core genera influencing the coagulation quality of milk. Additionally, specific genes of Lactobacillus helveticus, Limosilactobacillus fermentum, and Lactococcus lactis were found to be associated with the coagulation quality of fermented milk.