Microbial and flavor dynamics of medium-high temperature Daqu: regional influences and implications for Daqu quality...

Medium-high temperature Daqu (MHTD) plays a crucial role in Chinese strong-flavor Baijiu production, yet its microbial dynamics and the drivers of regional variation remain underexplored. In this study, we investigated the microbial community structure, enzyme activity, and flavor profiles of MHTD from three geographically adjacent regions in China, using metagenomic sequencing, E-sensory analysis, and multivariate statistics. Despite significant regional differences in microbial diversity, community composition, and taste, aroma profiles were relatively consistent. Redundancy analysis revealed that water content and acidity were the primary environmental drivers of microbial and flavor variation. Notably, increased water content was positively correlated with microbial richness, enzyme activity, and flavor complexity. Functional annotation of metagenomic data uncovered key microbial pathways for starch, cellulose, and lignin degradation, as well as for the biosynthesis of pyrazines and guaiacol derivatives. Limosilactobacillus fermentum, the dominant species across all samples, was found to possess the genetic potential to produce both compound classes-representing a novel finding. Fungal species such as Thermoascus sp. and Rasamsonia emersonii appeared to cooperate in guaiacol synthesis, while Acetobacter pasteurianus and A. oryzoeni in MHTD from Chuzhou City contributed to pyrazine production. These findings highlight the microbial and environmental basis of flavor formation in MHTD and offer practical implications for MHTD production. Specifically, moisture regulation during fermentation and selective enrichment of functional strains like L. fermentum and Acetobacter spp. may help optimize flavor development and product consistency.