Associations of microbial communities with metabolites and enzyme activities in different colors of high-temperature Daqu.

The distinctions among three types of high-temperature Daqu (yellow, white, and black Daqu) remain insufficiently characterized. In this study, we collected Daqu samples at different fermentation timepoints (days 8, 15, and 40) to analyze their enzyme activities, microbial diversity, and metabolomic profiles. Enzymatic analysis revealed that white Daqu exhibited significantly higher amylase and neutral protease activities compared with black Daqu and yellow Daqu. Through Illumina MiSeq sequencing, five dominant bacterial genera and six dominant fungal genera were identified in fermentation process. Microbial community analysis revealed that Bacillus and Scopulibacillus were the dominant bacterial genera in white Daqu, whereas Kroppenstedtia, Saccharopolyspora, Thermoascus, Saccharomyces, and Aspergillus dominated black Daqu. Non-targeted metabolomics indicated that carboxylic acids and derivatives, fatty acyls, organooxygenated compounds, and substituted benzene derivatives represented the majority of the differentially abundant metabolites. Moreover, black Daqu contained the highest number of differentially abundant metabolites compared to yellow and white Daqu. Correlation analysis demonstrated that Bacillus and Scopulibacillus showed significant positive correlations with neutral protease and amylase activities. Furthermore, Saccharopolyspora and Thermoascus exhibited strong positive correlations with metabolites involved in arginine and proline metabolism. This study provides valuable insights for optimizing traditional fermented food industry.