Microbial community succession, functional dynamics, and fermentative characteristic of yeasts in the fermented grains of strong-flavor Baijiu.

To elucidate the succession patterns and functional characteristics of microbial community during the fermentation of Strong-flavor Baijiu, this study integrated metagenomics, flavor analysis, and pure culture approaches to systematically investigate the dynamic changes in the microecosystem of fermented grains over 0-60 days of fermentation. In addition, the fermentative performance and environmental adaptability of the core yeast strains were evaluated. The results showed that Daqu-derived microorganisms (e.g., Kroppenstedtia and Rhizopus) dominated the early fermentation stage, whereas lactic acid bacteria (e.g., Lactobacillus and Acetilactobacillus) and yeasts (e.g., Pichia) became predominant in the late stage. Fungal community succession occurred earlier than that of bacteria. Functional annotation revealed that metabolic pathways related to carbohydrate metabolism and pyrimidine biosynthesis continuously increased throughout fermentation, with Firmicutes being the primary contributors. In the middle and late fermentation stages, the abundance of alcohol dehydrogenase (ADH) genes increased significantly, with Saccharomyces and the non-Saccharomyces yeast Pichia being the main contributors. Acidity and ethanol were identified as key drivers shaping microbial community succession, and most flavor compounds, such as ethyl acetate, predominantly accumulated during the middle-to-late fermentation stages. The two non-Saccharomyces yeasts, Pichia kudriavzevii Pk1 and Wickerhamomyces anomalus Wa9, exhibited both robust ethanol fermentation capacity and a desirable metabolic profile characterized by "high ester production with low 3-methyl-1-butanol formation." This study systematically reveals the temporal succession and functional dynamics of the microbial community during strong-flavor Baijiu fermentation and provides valuable microbial resources for targeted fermentation enhancement and the development of functional starter cultures.