Microbiomics and metabolomics insights into the microbial regulation on the formation of flavor components in the traditional fermentation process of Chinese <i>Hongqu</i> aged vinegar

Abstract

This study aimed to investigate microbial succession and metabolic dynamics during the traditional fermentation of <em>Hongq</em><em>u</em> aged vinegar, and explore the core functional microbes closely related to the formation of flavor components. Microbiome analysis demonstrated that <em>Lactobacillus</em>, <em>Acetobacter</em>, <em>Bacillus</em>,<em> Enterobacter</em>, <em>Lactococcus</em>, <em>Leuconostoc</em> and <em>Weissella </em>were the predominant bacterial genera, while <em>Aspergillus piperis</em>, <em>Aspergillus oryzae</em>, <em>Monascus purpureus</em>, <em>Candida athensensis</em>, <em>Candida xylopsoci</em>, <em>Penicillium ochrosalmoneum </em>and<em> Simplicillium aogashimaense </em>were the predominant fungal species. Correlation analysis revealed that <em>Acetobacter</em> was positively correlated with the production of tetramethylpyrazine, acetoin and acetic acid, <em>Lactococcus </em>showed positive correlation with the production of 2-nonanone, 2-heptanone, ethyl caprylate, ethyl caprate, 1-hexanol, 1-octanol and 1-octen-3-ol, <em>Candida xylopsoci</em> and <em>Candida rugosa</em> were positively associated with the production of diethyl malonate, 2,3-butanediyl diacetate, acetoin, benzaldehyde and tetramethylpyrazine. Correspondingly, non-volatile metabolites were also detected through UPLC-QTOF/MS. A variety of amino acids and functional dipeptides were identified during the traditional brewing of <em>Hongq</em><em>u</em> aged vinegar. Correlation analysis revealed that <em>Lactobacillus</em> was significantly associated with DL-lactate, indolelactic acid, D-(+)-3-phenyllactic acid, pimelic acid, pregabalin and 3-aminobutanoic acid. This study is useful for understanding flavor formation mechanism and developing effective strategies for the suitable strains selection to improve the flavor quality of <em>Hongqu</em> aged vinegar.