Abstract: In this study, some chemical properties including pH, carbohydrates, organic acids and free fatty acids of a fermentation starter for dietotherapeutic koumiss in Kerqin, Inner Mongolia were analyzed. To investigate the diversity of the bacterial community in the starter culture, second-generation sequencing of the V3-V4 region of the 16S rDNA genes was performed on the Illumina MiSeq platform. Thereafter, the species abundance, distribution and alpha diversity were analyzed. The analytical results indicated that the pH averaged at 3.54; the mean values of lactose and galactose were (0.281 ± 0.011)% and (0.100 ± 0.003)% respectively, and no glucose was detected. The levels of lactic acid, propanoic acid, acetic acid and butyric acid were (1.506 ± 0.069)%, (0.053 ± 0.002)%, (0.345 ± 0.014)%, and (1.143 ± 0.061)%, respectively. A total of 19 fatty acids were detected, including 12 saturated fatty acids and 7 unsaturated fatty acids. α-Linolenic acid was the most abundant unsaturated fatty acid at a level of (14.12 ± 0.36) mg/L. The results of bacterial diversity detection showed that (62 082.7 ± 4 868.8) clean reads were obtained, and the number of operational taxonomic units (OTUs) was 34.3 ± 2.3. The rarefaction curve showed that the sequencing depth was sufficient and the number of OTUs was close to saturation. The bacteria community in this sample was mainly distributed in the following 4 genera: Lactobacillus (84.08%), Acetobacter (9.83%), Lactobacillus (2.41%), and Streptococcus (2.18%) with the dominant genus being Lactobacillus. The above results showed that this fermentation starter sample was rich in unsaturated fatty acids and probiotics, and could guarantee food safety.

Key words: koumiss, fermentation starter, chemical composition, high-throughput sequencing, bacterial diversity