Bacterial microbiome and flavor metabolome shifts in traditional Hinggan league sauerkraut fermentation.

Microbial diversity is crucial for the flavor and quality of fermented vegetables. The unique geography and fermentation techniques of Hinggan League, Inner Mongolia, endow local sauerkraut with distinctive characteristics; however, the association between its microbiota and metabolites, as well as the underlying flavor formation mechanism, remains unclear, representing a gap in current research. Therefore, this study systematically investigated the interactions between microbial communities and metabolites during traditional sauerkraut fermentation in Hinggan League, Inner Mongolia, before and after fermentation. Using MiSeq sequencing technology, the core microbiota was identified, mainly including Lactobacillus, Halomonas, and Psychrobacter, with specific strains Azospirillum and Aureimonas observed exclusively in pre-fermentation (VC) samples. Metabolomics analysis detected a total of 335 abundant metabolites, among which 146 upregulated metabolites such as organic acids, amino acids, and fatty acid derivatives significantly accumulated during the late fermentation stage. Notably, 3-phenyllactic acid and 5-aminovaleric acid were the most representative characteristic metabolites. Metabolites pathway enrichment analysis revealed that arginine and proline metabolism, alanine/aspartate/glutamate metabolism, and cyanoamino acid metabolism were the major pathways significantly activated during fermentation, closely associated with energy metabolism, acid-base homeostasis regulation, and flavor generation. Correlation analysis showed a strong association between Lactococcus and 31 flavor compounds, including palmitic acid, L-phenylalanine, and heptadecanoic acid. Functional annotation indicated that Lactococcus-driven protein degradation, amino acid conversion, and lipolytic activities generate key precursors for sour and umami flavor development. Collectively, this study elucidates the microbial community succession characteristics, inter-microbial interaction patterns, and the associated metabolic regulation mechanisms of flavor formation during sauerkraut fermentation, providing a theoretical basis for the targeted modulation of characteristic flavor compound synthesis and the optimization of traditional fermentation processes.