Dynamic changes and correlations of microbial communities, physicochemical properties, and volatile metabolites during Daqu fermentation of Taorong-type Baijiu

Daqu is an important saccharification starter in the brewing of Chinese Baijiu. The evolution of microbial communities and flavor formation are similar among different batches of Daqu, but the drivers of microbial community succession, the composition of functional microbiota, and metabolic pathways are still unclear. To this end, the microbial community succession, physicochemical properties and volatile metabolites dynamic changes and their correlation during the fermentation process of Taorong-type Baijiu Daqu were analyzed. The results showed that the core microbial genera observed in the whole period were Bacillus, Kroppenstedtia, Microbacterium, Thermoascus, Saccharomycopsis, and Apiotrichum. The correlation analysis showed moisture content and acidity drove the evolution of functional microbial communities in the Daqu. Visualized network analysis demonstrated that changes in the relative abundance of functional microbiota such as Bacillus, Kroppenstedtia, Thermomonas, Saccharomycopsis, Thermoascus and Malassezia promoted the difference of metabolism in different stages of Daqu fermentation. PICRUSt2 prediction and volatile metabolite metabolic pathway enrichment analysis showed that the metabolism of Daqu fermenting microorganisms was concentrated on amino acid, carbohydrates and energy metabolism. Our findings will facilitate the standardized production of stable-quality Daqu, and theoretically underlie Baijiu brewing microecological assembly and directional controllable fermentation.