Deciphering microbial dynamics and functional diversity during different rounds of pit fermentation of jiang-flavor Baijiu

The variation in microbiota during pit fermentation is the main reason for the distinct characteristics of the seven types of base Baijiu in Jiang-flavor Baijiu (JFB) brewing. However, the specific structure and succession of microbial communities at different rounds of fermentation, and functional differentiations remain unclear. Therefore, this study compared the differences in microbiota structure, environmental factors driving community assembly, and functional differentiations throughout 1-7 rounds of pit fermentation in JFB production. Results showed that <em>Lactobacillus</em> dominated all rounds and complied with declining relative abundance from rounds 1-7. The mould composition was similar in JC3-JC5 while the yeast structure in JC4 was found intermediate between JC3 and JC5. LEfSe2 analysis unveiled aroma-producing microorganisms as prominent biomarkers in JC1, strong enzyme-producing attributes in JC2, JC6, and JC7 biomarkers, and an enzyme and aroma-producing focus with robust tolerance in JC3-JC5 biomarkers. Acidity mainly regulated the microbial community in the first four rounds, with nutrient limitation driving microbial succession from the fifth round onward. Functional predictions underscored enriched amino acid metabolism enzymes in JC6 and JC1, while carbohydrate degradation exhibited predominant enzymatic profiles in JC2, JC6, and JC7. This study laid a foundation for comprehending community composition, succession, and flavor regulatory mechanisms throughout JFB brewing.