Exploring the impacts of traditional crafts on microbial community succession in Jiang-flavored Daqu.

The usage of traditional crafts during the fermentation process has a great influence on the quality of Jiang-flavored Daqu. This study focused on exploring the impacts of traditional crafts on Daqu microecology through high-throughput sequencing and statistical analyses. These results show that traditional crafts modulated microbial community succession through the regulation of temperature, moisture, and acidity. High temperatures (66 ± 1 °C) were conducive to the growth of microbes that produced flavor compounds, such as Bacillus and Thermoactinomyces. Low moisture content (correlated with 22 genera) and high acidity (8 genera) were mainly responsible for the decreased microbial diversity. Two flipping processes showed significant effects on the internal microecology and microbial metabolism. The first flip of Daqu may assist in regulating the microbial community structure and promoting the enrichment of flavor-functional microorganisms. The second flipping was reasonable for the enrichment of esterifying functional microorganisms, thus enhancing the esterifying power of Daqu with reduced acidity. Furthermore, analysis of the metabolic pathways at different stages of the process showed that the levels of flavor precursors and secondary metabolites within Jiang-flavored Daqu significantly increased during fermentation.