Comparative Analysis of Microbial Community Structure and Functional Traits of Baijiu Daqu Across Diverse Geographical Regions in China

Daqu is a key starter used in Baijiu production, and its microbial composition and associated metabolic functions play critical roles in fermentation performance and flavor development. This work aimed to reveal how Daqu-making temperature regulates microbial community divergence and subsequent metabolite formation via multi-omics analysis so as to provide theoretical guidance for Daqu quality control. In this study, physicochemical analysis, metagenomic sequencing, and metabolomic profiling were combined to investigate the microbial community structure, functional differentiation, and metabolite characteristics of nine Daqu samples collected from six major Baijiu-producing regions in China. The temperature during Daqu preparation was found to be a primary factor driving microbial community assembly and functional specialization. Medium-temperature Daqu exhibited higher saccharifying activity (up to 867 U) and greater microbial diversity with the enrichment of amino acid metabolism-related pathways, indicating enhanced protein degradation and amino acid utilization for the formation of flavor precursors. In contrast, high-temperature Daqu showed stronger capacities for carbohydrate degradation and conversion, particularly in starch and sucrose metabolism, which were closely associated with the enrichment of thermotolerant fungi and bacteria. LEfSe analysis identified 47 distinct microbial biomarkers (LDA score > 3.0), which could differentiate between medium- and high-temperature Daqu. Redundancy analysis indicated that environmental factors (moisture and acidity) together with functional properties (fermentation, esterification, liquefaction, and saccharification) act as key drivers of microbial functional patterns. Metabolomic analysis further revealed that medium-temperature Daqu had higher abundances of esters and fatty acids, whereas high-temperature Daqu had higher proportions of alcohols and ketones. Taken together, these results provide a multi-omics perspective on temperature-driven microbial functional differentiation in Daqu and offer a scientific basis for quality-oriented regulation and process optimization in Baijiu production.