Metagenomic analyses reveal microbial communities and functional differences between Daqu from seven provinces.

Microbial communities perform the brewing function in Daqu. Macrogenomics and PICRUST II analyses revealed the differences in microbes and metabolic functions among Daqu from the seven Baijiu-producing provinces. Jiang-flavored Daqu (Guizhou, Shandong, and Hubei provinces) generally forms an aroma-producing functional microbiota with Kroppenstedtia, Bacillus, Thermoascus, Virgibacillus, and Thermomyces as the core, which promotes the metabolism of various amino acids and aroma compounds. Light-flavored Daqu (Shanxi Province) enriched the Saccharomycopsis, Saccharomyces, and lactic acid bacteria (LAB) microbiota through low-temperature fermentation. These microbes can synthesize alcohol and lactic acid but inhibit amino acid metabolism within the Light-flavored Daqu. Bifidobacterium and Saccharomycopsis were dominant in the Tao-flavored Daqu (Henan province). This unique microbial structure is beneficial for pyruvate fermentation to lactate. Research also found that Strong-flavored Daqu from Jiangsu and Sichuan provinces differed significantly. The microbial communities and metabolic pathways within Jiangsu Daqu were similar to those within Jiang-flavored Daqu, but Sichuan Daqu was dominated by Thermoascus, LAB, and Thermoactinomyces. In addition, Spearman correlation analysis indicated that Kroppenstedtia, Bacillus, and Thermomyces were not only positively related to flavor metabolism but also negatively correlated with Saccharomycopsis. This research will help establish a systematic understanding of the microbial community and functional characteristics in Daqu.

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.