Microbial diversity and its relationships with stress factors in sesame-flavor liquor fermentation process

Abstract:

[Background] In recent years, the production technology of sesame-flavor liquor is becoming more and more mature. But the corresponding scientific research has not developed synchronously. High-throughput sequencing technology is increasingly used in the study of species diversity, but it focuses on the relative abundance of species rather than the microbial number of species. [Objective] The changes of microbial community structure and its correlation with stress factors during the fermentation of sesame-flavor liquor were analyzed, and the correlation between main yeasts and bacteria was also studied, to provide theoretical support for revealing the fermentation mechanism and controlling fermentation quality of sesame-flavor liquor. [Methods] The microbial community structure during the fermentation of sesame-flavor liquor was determined by traditional quantification of microorganisms and sequencing the bacterial 16S rDNA gene and the fungal ITS rDNA gene using Thermofisher?s Ion S5TMXL sequencing platform. The contents of lactic acid, acetic acid and ethanol during the fermentation process were monitored. The microbial community and its relationship with stress factors during fermentation were analyzed by complexity analysis of samples, comparative analysis of samples and correlation analysis of environmental factors. The correlation between yeasts and bacteria was analyzed by Pearson correlation. [Results] Cellulose bacteria, Westermania and Bacillus were dominant in the early fermentation stage, and Lactobacillus was dominant in the middle and late fermentation stages, followed by cellulose bacteria, Westermania and Bacillus. Issatchenkia was the dominant yeast in the whole fermentation process, followed by Wickerhamomyces, Saccharomyces cerevisiae and Candida. Most microorganisms were negatively correlated with stress factors, and only Lactobacillus showed a significant positive correlation with acetic acid. Yeasts were positively correlated with some bacteria. [Conclusion] The interaction of stress factors and microbes in liquor fermentation process promoted the succession process of the community. The organic acids produced by Lactobacillus and Bacillus during the late stage of fermentation inhibited most of the acid-nonresistant microorganisms, and organic acids were the main stress factors affecting community structure. The combination of microbial quantity and relative abundance revealed more information about the succession of community structure and its correlation with environmental factors during fermentation.