Temperature-driven functional microbial interactions in soy sauce fermentation: Effects of Zygosaccharomyces rouxii and Wickerhamiella versatilis on flavor enrichment and biogenic amine reduction.

This study elucidates the temperature-dependent interactions between halotolerant yeasts and microbial communities during secondary fortified soy sauce fermentation (SFFSS) and their implications for flavor enhancement and safety. A dual-mode fermentation system compared natural temperature fermentation (NTF) and controlled temperature fermentation (CTF, 30 °C), each with and without co-inoculation of Zygosaccharomyces rouxii and Wickerhamiella versatilis (ZC). Multi-omics analyses integrating amplicon sequencing, metagenomics, and metabolomics revealed that CTF control elevated amino acid nitrogen and aroma compounds, while increasing biogenic amines (BA) by 47.88 %. In both NTF and CTF modes, the ZC pattern significantly reduced lactic acid while enhancing succinic acid, umami/sweet free amino acids, and key aroma compounds (e.g., 4-ethylguaiacol, 5-ethyl-4-hydroxy-2-methyl-3(2H)-furanone), alongside enriching functional bacteria (Staphylococcus, Weissella), stabilizing fungal communities, and suppressing Tetragenococcus and Ligilactobacillus pobuzihii. Mechanistically, ZC pattern promoted tricarboxylic acid cycle flux and amino acid metabolism, synergistically enhancing volatile phenolics, esters, and alcohols, and reduced BA by >87 % via dual modulation of decarboxylase inhibition and oxidase activation. Network analyses linked microbial composition shifts to targeted flavor metabolite synthesis, providing a mechanistic framework for microbial community engineering. These findings highlight yeast-mediated, temperature-driven modulation of microbiota-metabolite networks as a viable strategy for producing high-quality, safe soy sauce with optimized flavor complexity.