Comprehensive analysis for the bioturbation effect of space mutation and biofortification on strong-flavor Daqu by high-throughput sequencing, volatile analysis and metabolomics

Daqu, an indispensable starter, significantly affects the quality and yield of Chinese baijiu. To explore the bioturbation effect of space mutation and biofortification on strong-flavor Daqu, the microbial community, physicochemical properties and overall metabolic profile were investigated. Lactobacillus and Aspergillus were significantly reduced after bioturbation, while seven genera (e.g., Bacillus and Pichia) and five genera (e.g., Enterococcus and Thermomyces) were enriched by space mutation and biofortification, respectively, resulting in improved enzymatic activities. Among the 14 aroma-active volatiles and 51 differential metabolites identified, most had a higher content after bioturbation, including pyrazines, alcohols, small peptides and carbohydrates. Moreover, correlation analysis and integrated metabolic pathway showed that differences in flavor quality among these Daqu were mainly associated with bacterial communities, especially Bacillus, Kroppenstedtia, Thermoactinomyces and Scopulibacillus. These results are useful for elucidating the mechanism of flavor formation in Daqu and promoting the further application of bioturbation technology in the traditional fermentation industry.