Construction of Synthetic Microbial Community with Core Microorganisms for Soy Sauce Fermentation

Core microbes and succession of the microbial community greatly influence soy sauce fermentation process. This study identified seven functionally important core microbes, including Weissella paramesenteroides, Lactiplantibacillus plantarum, Tetragenococcus halophilus, Pediococcus pentosaceus, Zygosaccharomyces rouxii, Candida orthopsilosis, and Aspergillus oryzae for soy sauce fermentation, based on dominant taxa, co-occurrence relationships, and volatile-associated taxa analysis. Four distinct fermentation phases were identified for soy sauce fermentation based on metagenomics and metabolomics data correlation analyses. Acceptable fermentation performance and comparable soy sauce flavor compounds were achieved using a temporal synthetic microbial community for fermentation. The synthetic microbial community was assembled with inoculation of dominant lactic acid bacteria (LAB) in the immediate early phase, other LAB in early and middle phases, and yeasts in the late phase. Glutamate and 4-ethylguaiacol were identified as soy sauce fermentation indicators for early to middle and late fermentation phases, respectively. These results may provide a possible solution for achieving precise control over the brewing process and improving the flavor and quality of soy sauce.