Predominant lactic acid bacteria in traditional fermented yak milk products in the Sichuan Province of China

Yak milk products have been consumed for hundreds of years in the Sichuan province of China where complex microbial populations contribute to their unique flavor and functional properties. Sixty-four samples of traditional yak milk products (kurut, qula cheese, raw milk, whey, and butter) were collected from widely distributed households in Sichuan province, China. In total, 213 strains of lactic acid bacteria (LAB) were obtained by traditional pure culture method and all strains were identified to species level by phenotypic characterization, 16S rRNA gene sequence analysis, species-specific PCR, and tuf-PCR-RFLP technologies. The result showed that a complex LAB composition was present in these products, and all the isolates belonged to six genera and 17 different species and subspecies. The distribution of the isolates by genus was as follows: (40.8%), (39.0%), (13.2%), (5.6%), (0.94%), and (0.46%). Among these isolates, subsp. (61 strains, about 28.6%) and (41 strains, about 19.2%) were the predominant populations in yak milk samples. This paper systematically studied the LAB composition in various yak milk products in Sichuan province of China, which provides raw data and LAB strain resource for further studies involving probiotic strain selection and starter culture design pertaining to the industrial production of traditional fermented milk.