Cross-kingdom metabolic coordination enhances flavor formation in Sauce-aroma Baijiu fermentation using a defined...

Cross-kingdom microbial interactions, particularly between bacteria and yeast, play a central role in shaping flavor formation in complex solid-state fermented foods, yet the underlying causal mechanisms remain insufficiently resolved. In this study, a defined three-strain synthetic consortium-Bacillus halotolerans G47, Lactiplantibacillus plantarum F15, and Pichia kudriavzevii K44-was constructed to elucidate metabolic cooperation during sauce-aroma Baijiu fermentation. A simplified laboratory-scale solid-state sorghum model was used to characterize microbial dynamics, physicochemical changes, and volatile metabolite formation, while a nutritionally equivalent liquid system enabled multi-species transcriptomic profiling. Mixed-culture fermentation substantially increased the production of key odor-active compounds, particularly ethyl esters, acetate esters, and phenolic derivatives, which showed the most pronounced enhancement. Transcriptomic integration revealed coordinated metabolic reprogramming across the three species, redirecting carbon and nitrogen fluxes toward flavor-related pathways. G47 enhanced aromatic amino acid degradation and phenolic acid decarboxylation; F15 intensified carbohydrate catabolism and organic acid biosynthesis; and K44 activated fatty-acid turnover, alcohol metabolism, and ester-associated pathways. These complementary metabolic shifts collectively promoted ester biosynthesis and phenolic aroma formation. This work demonstrates that enhanced flavor formation arises from interaction-driven metabolic coordination rather than additive single-strain activity. The defined consortium provides a tractable platform for mechanistic investigation and offers a rational basis for designing functional microbial communities to improve flavor quality in solid-state fermented foods.