Abstract
Qula is a cheese-like product usually prepared with unpasteurized yak milk under open conditions, with both endogenous and exogenous microorganisms involved in the fermentation process. In the present study, 15 Qula samples were collected from five different regions in China to investigate the diversity of microbial communities using high-throughput sequencing targeting the V3–V4 region of 16S rRNA gene. The bacterial diversity significantly differed among samples of different origins, indicating a possible effect of geography. The result also showed that microbial communities significantly differed in samples of different origin and these differences were greater at the genus than the phylum level. A total of six phyla were identified in the samples, and Firmicutes and Proteobacteria had a relative abundance >20%. A total of 73 bacterial genera were identified in the samples. Two dominant genera (Lactobacillus and Acetobacter) were common to all samples, and a total of 47 operational taxonomic units at different levels significantly differed between samples of different origin. The predicted functional genes of the bacteria present in samples also indicated differences in bacterial communities between the samples of different origin. The network analysis showed that microbial interactions between bacterial communities in Qula were very complex. This study lays a foundation for further investigations into its food ecology.
Highlights
The yak is the only bovine species adapted to the cold and harsh conditions of the Hindu Kush-Himalayan region and the Qinghai–Tibetan Plateau with its altitude range of 2,000–5,000 m above sea level (Cui et al, 2016)
Because Qula is usually prepared with unpasteurized yak milk under open conditions, both endogenous and exogenous microorganisms are involved in the fermentation process
Sequencing and classification Total DNA was extracted from the Qula samples, after which V3–V4 of the 16S rRNA gene was PCR amplified from each DNA sample
Summary
The yak is the only bovine species adapted to the cold and harsh conditions of the Hindu Kush-Himalayan region and the Qinghai–Tibetan Plateau with its altitude range of 2,000–5,000 m above sea level (Cui et al, 2016). In China, there are about 14 million yak distributed in Yunnan, Xizang, Qinghai, Gansu, Sichuan, and other provinces, accounting for 95% of the world’s yak population. Yak have been central to the development of the farming and pastoral communities of these areas (He et al, 2011). Qula is a traditional homemade fermented cheese-like yak milk. Because Qula is usually prepared with unpasteurized yak milk under open conditions, both endogenous and exogenous microorganisms are involved in the fermentation process. It is obvious that these methodologies are not optimal to provide detailed information regarding the microbial communities in complex matrixes for technique limitations (Li et al, 2011; Ao et al, 2012; Ding et al, 2017)
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