Metagenomic insights into microbial community succession and its functional changes during the stage of acetic acid fermentation of shanxi aged vinegar.

Traditional fermentation of Shanxi aged vinegar involves complex microbial interactions driving flavor synthesis, but the mechanisms underpinning metabolic adaptation and community succession remain poorly characterized. This study aimed to unravel stage-specific microbial dynamics and their functional contributions to flavor formation during Cupei fermentation. Metagenomic sequencing analyzed microbial communities and metabolic pathways at three fermentation stages (D3, D6, D9). Functional annotation (KEGG, CAZy) and species-level contribution assessments identified key taxa and genes linked to flavor biosynthesis. Microbial succession shifted from Lactobacillus dominance (64.68% at D3) to Acetobacter prevalence (48.04% at D9), with Lactobacillus acetotolerans persisting throughout (17.15-26.23%). Early-stage carbohydrate metabolism (GHs-driven: 60.38% at D3) transitioned to late-stage amino acid (15.62%) and cofactor synthesis (12.17%), activating valine, leucine, and histidine pathways critical for flavor compounds. Acetobacter oryzoeni and Acetobacter pomorum drove acetate (ALDH: 27.07-41.52%), valine (ilvE: 53.21-20.22%), and histidine (hisD: 41.83-33.30%) metabolism at D9. Low abundance species (Weissella confusa, 0.51%) and uncultured Limosilactobacillus sp. contributed via multi-gene networks (e.g., dat, ldh), which revealed an important functional contribution by overlooked low-abundance species. The study uncovers ecological coupling between microbial succession and metabolic adaptation, where dominant taxa and rare species synergistically govern flavor formation. These insights enable targeted microbial community design for flavor optimization in traditional fermented foods.