Reduced lactic acid strengthens microbial community stability and function during Jiang-flavour Baijiu fermentation

Unravelling the relationships between microbial community stability and function under environmental stress is critical to understanding microbial ecology but remains understudied in fermentation ecosystems. In this study, the relationship between lactic acid and microbial community was revealed during Jiang-flavour Baijiu fermentation using high-throughput sequencing and nontargeted metabolomics. Lactic acid was reduced by mono- and co-inoculation of lactic acid-degrading strains, Pichia kudriavzevii and Zygosaccharomyces bailii. Furthermore, reduced lactic acid strengthened microbial community stability, mainly characterized by higher network modularity and more positive interactions of species. Lactic acid had a significantly negative relation with network modularity (P = 0.03, Pearson's r = − 0.97). Moreover, the increase in network stability contributed to stronger community function, as indicated by the increase in ethanol, total esters, and total alcohols. Finally, metabolic function analysis showed that amino acid metabolism, starch and sucrose metabolism, pyruvate metabolism, the TCA cycle, nucleotide sugar metabolism, pyrimidine metabolism, and purine metabolism were the main pathways resulting in changes in microbial community stability and function. This study indicated that microbial community stability and function can be enhanced by the regulation of environmental factors and provided a possible strategy for the steady-state regulation of the microbial community in Baijiu fermentation.