Characteristics and correlation of the microbial communities and physicochemical factors from pit mud of Strong-flavor Baijiu

To gain a deeper understanding of the role microorganisms play in shaping the quality of baijiu, this study comprehensively examined the microbial communities and physicochemical characteristics of pit mud (PM) sourced from various ages (20, 30, 40, and 50 years) and distinct spatial layers, as well as explored the correlations between these factors. Fungal communities in PM had lower diversity and richness than prokaryotic microorganisms. Microbial diversity decreased with increasing PM age at the same spatial location. In the same aged PM, the middle layer had higher prokaryotic microbial diversity, while the upper and middle layers had higher eukaryotic microbial diversity. Firmicutes and Ascomycota are dominant prokaryotic and eukaryotic phyla, respectively. At the genus level, 19 prokaryotic and 16 eukaryotic dominant genera were detected. Lactobacillus was predominant in the upper and middle layers, and Caldicoprobacter was more abundant in 20- and 30-year-old PM. Among eukaryotes, Kazachstania dominated in younger PM, and Priceomyces was unique to 50-year-old PM. Physicochemical analysis showed that moisture and available phosphorus increased, while pH and ammonia nitrogen decreased with PM age. Significant differences in pH and ammonia nitrogen were observed among spatial locations. Spearman correlation analysis indicated that Methanobacterium and Thermoascus abundance were significantly correlated with pH, ammonia nitrogen, and available phosphorus. The research reveals notable spatial and temporal differences in microbial taxa and their influence on physicochemical indices. It offers valuable insights for the management of pit mud (PM) and the production of high-quality baijiu, underscoring the importance of considering spatial factors and optimizing fermentation performance.