Characterization of physicochemical properties, volatile compounds and microbial community structure in four types of Daqu

Daqu is one of the most important fermentation starters for Baijiu production, and different types of Daqu have been reported. However, the different types of Daqu are poorly understood. In the present study, four types of Daqu were thoroughly characterized based on biochemical composition, volatile compounds and microbial community structure. Significant differences were observed in physicochemical properties in the four types of Daqu analyzed herein (p < 0.05). Moreover, 48 volatile components were detected in samples, thus enabling the identification of 18 discriminant markers of volatile compounds in the four types of Daqu. In addition, differences in the microbial community structure of four types of Daqu were observed, including 46 differential species. Fungi had a great influence on carbon metabolism potential, and peak temperature of Daqu was negatively correlated with carbon metabolism capacity. Conversely, bacteria had a more notable effect on nitrogen meta-bolism, and peak temperature of four types of Daqu was positively correlated with nitrogen metabolism capacity. Thus, the findings discussed herein shed a light onto the differences of four types of Daqu, thereby contributing to expanding the current knowledge on the traditional industrial fermentation starter for Baijiu production.