Comparative analysis of microbial communities and physicochemical attributes of strong-aroma Daqu from Southwestern China

Daqu is a critical saccharifying and fermenting agent in the traditional solid-state production of strong-aroma Baijiu, with its physicochemical properties and microbial communities playing a vital role in both starter quality and final aroma. This study analyzed twelve Daqu samples from four key production regions in Sichuan Province-Luzhou (L), Suining (S), Yibin (Y), and Zigong (Z)-assessing physicochemical parameters such as moisture content, acidity, saccharification, liquefaction, and esterification activities. Microbial communities were characterized using Illumina high-throughput sequencing. Regional variations in physicochemical properties were observed, with Y showing the highest acidity, saccharification, and esterification activities. While no significant regional differences in alpha-diversity were found, β-diversity analysis (PCoA) revealed distinct microbial structures. Bacteria were predominantly represented by Bacillus, Lactobacillus, and Weissella, while Aspergillus, Saccharomycopsis, and Rhizopus dominated fungi. LEfSe analysis (LDA ≥ 4.0) identified region-specific microbial shifts. PICRUSt2 and FUNGuild predictions indicated significant potential for amino acid and carbohydrate metabolism, with saprotrophic fungi being dominant. Correlation analysis highlighted Thermoactinomyces, Weissella, Bacillus, and Rhizopus as key microbes influencing saccharification, starch degradation, and esterification. These findings provide insights into microbial and biochemical factors driving regional differences in Daqu, offering a foundation for standardized production methods and quality control.