Research Article: Multi-omics profiling of microbial ecology and non-volatile compounds across fermentation stages of spontaneous litchi ( Litchi chinensis Sonn.) fermented vinegar-like beverage

Abstract:
Litchi fruit vinegar-like beverages (LVBs) are notable processed products derived from litchi fruit, yet few studies have focused on the systematic characterization of microbial and metabolic dynamics during their natural fermentation process. This work employed a comprehensive methodology integrating metagenomics and untargeted metabolomics based on UHPLC–MS/MS (Orbitrap Q Exactive HF-X) to elucidate the dynamic profiles of the microbial community and non-volatile metabolites, as well as their interrelations, across the various spontaneous fermentation stages of LVBs. Metagenomic analysis indicated reduced microbial diversity and substantial structural changes within the community. Bacteria dominated the fermentation, accounting for 69.16 – 99.04% of the microbial community based on the taxonomically classified reads at the kingdom level. During the preliminary stage, Leuconostoc , Enterobacter , and Klebsiella were the prevalent genera. During the mid-fermentation stage, Komagataeibacter and Lactiplantibacillus emerged as the predominant genera in acid production. In the final stage, the microbial community was dominated primarily by Zymomonas and the Acetobacteriaceae family, including Acetobacter and Komagataeibacter . The non-targeted metabolomics study identified 2,382 metabolites through comprehensive database matching (in-house library, HMDB, KEGG, and metDNA algorithm) and stringent quality filtering (identification score > 0.5 and QC CV < 0.5), which were categorized into 20 distinct groups. Thirty seven metabolites, including amino acids, organic acids, and benzene derivatives, were identified as probable distinct differential metabolites based on a p -value threshold of p <?0.05, VIP > 1.0, and a fold change (FC ? 2 or ? 0.5) between consecutive fermentation stages in pairwise OPLS-DA of litchi vinegar-like beverage fermentation. Spearman correlation analysis revealed a highly organized ecological interaction network among dominant bacteria, physicochemical parameters, and non-volatile taste metabolites in the LVB fermentation system. Zymomonas mobilis , Acetobacter pasteurianus , Leuconostoc suionicum , and Lactiplantibacillus plantarum facilitated fermentation through metabolic synergy. Meanwhile, stage-specific enrichment of distinct Enterobacteriaceae species ( Enterobacter hormaechei , and Enterobacter quasiroggenkampii ) reflected species-level niche differentiation and resource competition, rather than a unified family-wide competitive behavior. These findings provide a theoretical framework for engineering synthetic consortia and bioaugmentation approaches, informing the selection of starters and co-cultures to enhance LVB sensory and bioactive properties, alongside facilitating sfruit valorization.

Introduction:
Litchi fruit vinegar-like beverages (LVBs) are notable processed products derived from litchi fruit, yet few studies have focused on the systematic characterization of microbial and metabolic dynamics during their natural fermentation process.

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