To study the microbial diversity of Inner Mongolia dry fermented dairy products, and its correlation with free amino acid and short-chain fatty acid composition, the 16s rDNA V4-V5 region of microorganisms in five dry fermented dairy products of Inner Mongolia was sequenced by high-throughput sequencing, and the bacterial diversity was analyzed. The contents of short-chain fatty acids and free amino acids were determined by GC-MS and HPLC, respectively. The results showed that the microorganism in milk dregs had the highest microbial community diversity and overall abundance. There were relatively considerable differences among the five samples in species composition of microbial communities. At genus level, Lactococcus and Lactobacillus were the dominant bacteria of Alurel, fermented milk curd and yogurt curd; Pseudomonas and Acinetobacter were the dominant bacteria of vrum; Lactococcus and Serratia were the dominant bacteria of milk dregs. Based on the principal component analysis (PCA), yogurt curd and fermented milk curd samples had the highest similarity of species composition. A total of 23 kinds of short-chain fatty acids were detected. Vrum contained the most kinds of short-chain fatty acids. Besides, a total of 24 kinds of free amino acids were detected; fermented milk curd contained 24 kinds of free amino acids, and the content was significantly higher than the other samples. There were significant differences among the five samples in the contents of short-chain fatty acids and free amino acid (P<0.05). According to the redundancy analysis (RDA), hydroxyproline and glutamate were positively correlated with Lactococcus and Lactobacillus. Besides, Pseudomonas was positively correlated with butyric acid, hexanoic acid, octanoic acid and decoic acid. This study reveals the relationship between microbial composition, short-chain fatty acids ,and free amino acid in the characteristic dry fermented dairy products of Inner Mongolia, and provides a certain theoretical basis for the development and optimization of traditional fermented dry dairy products industry.
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