Elucidation of core functional microbes and construction of flavor metabolic network during Zaolajiao fermentation

Zaolajiao (ZLJ) is a traditionally fermented vegetable product prized for its sour-spicy flavor. This study investigated the dynamic changes of microbial communities and metabolites during five representative fermentation stages, using an integrated multi-omics strategy combining metagenomics, metabolomics, and flavouromics. Taxonomic analysis revealed 3 kingdoms, 11 phyla, 193 genera, and 516 species, with 65 core genera persisting throughout the process. Among them, 23 dominant genera consistently maintained a combined relative abundance exceeding 85%. Lactic acid bacteria (e.g., Levilactobacillus , Lactobacillus ) and yeasts (e.g., Pichia , Wickerhamomyces ) exhibited distinct succession trajectories, indicating a shift from bacterial-dominated to fungal-enhanced phases. OPLS coupled with correlation network analysis identified seven core functional genera— Lactiplantibacillus , Companilactobacillus , Lactobacillus , Wickerhamomyces , Lentilactobacillus , Pediococcus , and Pichia —that were significantly correlated with key flavor-related metabolites, including organic acids, free amino acids, and volatile compounds. Notably, Pichia showed a strong positive correlation with total free amino acids (r ≥ 0.959, P < 0.01), while Wickerhamomyces exhibited an equally strong positive correlation with total organic acids (r ≥ 0.959, P < 0.01); conversely, the lactic acid bacteria genera were consistently negatively correlated with soluble sugars. These correlation patterns, combined with the co-occurrence of specific microbial taxa and metabolites, suggest that protein hydrolysis and carbohydrate catabolism serve as primary drivers of flavor generation.