Tarag is a characteristic fermented dairy product with rich microflora (especially lactic acid bacteria), developed by the people of Mongolian nationality in Inner Mongolia of China and Mongolia throughout history. One hundred and ninety-eight samples of Tarag were collected from scattered households in Eastern Inner Mongolia, and total of 790 isolates of lactic acid bacteria (LAB) were isolated by traditional pure culture method. To identify these isolates and analyze their biodiversity, 16S rRNA gene sequences analysis and PCR-DGGE were performed respectively. The results showed that 790 isolates could be classified as 31 species and subspecies. Among these isolates, Lactobacillus helveticus (153 strains, about 19.4%), Lactococcus lactis subsp. lactis (132 strains, about 16.7%) and Lactobacillus casei (106 strains, about 11.0%) were considered as the predominated species in the traditional fermented dairy products (Tarag) in Eastern Inner Mongolia. It was shown that the biodiversity of LAB in Tarag in Inner Mongolia was very abundant, and this traditional fermented dairy product could be considered as valuable resources for LAB isolation and probiotic selection.

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To determine which yeasts are present in the naturally fermented milks of China, 69 samples made by the nomads of Tibet were collected from the Tibetan Plateau in China. From these samples, 225 strains of yeast were isolated and identified using conventional microbiological analysis and gene sequencing analysis of the D1/D2 domain of the large subunit (26S) ribosomal DNA. The results showed that the total concentration of yeasts in these samples ranged from 5.01 to 8.97 log10 colony-forming units (CFU)/mL (6.91 ± 1.02 log10 CFU/mL; mean ± SD). The number of cultivable yeasts was higher in the samples from Qinghai (7.55 ± 0.75 log10 CFU/mL) than those from Tibet (6.21 ± 0.79 log10 CFU/mL, P < 0.05). Moreover, there were 15 phylotypes in these 69 samples. Among these phylotypes, Kluyveromyces marxianus (49.3%, frequency percentage), Saccharomyces cerevisiae (62.3%), and Pichia fermentans (46.4%) appeared frequently and can be considered the most common culturable species in naturally fermented milk products. Traditional fermented Mongolian cow milk featured a wide diversity of yeast species, including Issatchenkia orientalis, Kazachstania unisporus, Rhodotorula mucilaginosa, Candida pararugosa, Torulaspora delbrueckii, Geotrichum sp., Kazachstania unisporus, Geotrichum fragrans, Debaryomyces hansenii, Yarrowia lipolytica, Trichosporon gracile, and Pichia membranifaciens. This study provides new data on yeast composition in naturally fermented milk and shows the yeast biodiversity of fermented milk products from the Tibetan Plateau 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: Leuconostoc (40.8%), Lactobacillus (39.0%), Streptococcus (13.2%), Lactococcus (5.6%), Enterococcus (0.94%), and Weissella (0.46%). Among these isolates, Leuconostoc mesenteroides subsp. mesenteroides (61 strains, about 28.6%) and Lactobacillus helveticus (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.