Metagenomics and untargeted metabolomics analyses to unravel the formation mechanism of characteristic metabolites in mung bean sour liquid during different fermentation stages

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Abstract

Mung Bean Sour Liquid (MBSL), a traditional fermented food indigenous to Luoyang, China, acquires its distinctive organic properties and bioactivity through complex microbial metabolic interactions. To decode its dynamic microbial-metabolic network, this study integrated metagenomic sequencing and LC-MS metabolomics across four fermentation stages (1 h, 6 h, 12 h, 24 h). Results revealed Lactobacillus dominance (75.85–85.53 %) persistent through fermentation, when Lactococcus proliferated substantively in terminal phases(9.81 % at 24 h). Fungal communities exhibited stage-specific dynamics: Verticillium dahliae dominated early phases (43.89–49.98 %), whereas Tilletia controversa and Saccharomyces cerevisiae surged 3.3- and 8.3-fold by 24 h. Metabolomic profiling identified 84 key metabolites, including 20 functional peptides (e.g., His-Val, Tyr-Leu), 15 carbohydrates, and 10 lipids. Secondary metabolites (coumarins, terpenoids, lactones) accumulated mid-to-late fermentation, contributing sweet/nutty notes, antioxidant activity, and antimicrobial effects. Correlation analysis uncovered genus-specific metabolic roles: Lactococcus species positively associated with lipid oxidation products (e.g., cis-9,10-epoxystearic acid), while Lactobacillus plantarum regulated organic acid metabolism. Fungal genera (e.g., Penicillium italicum, Tremella fuciformis) showed distinct metabolite correlations, suggesting cross-kingdom interactions. This study elucidates the microbial-metabolite interplay governing MBSL's flavor and functionality, providing insights for optimizing fermentation processes and developing functional ingredients.