Microbiomics and Metabolomics Insights into the Microbial Regulation on the Formation of Flavor Components in the Traditional Fermentation Process of Chinese Hongqu Aged Vinegar

This study aimed to investigate microbial succession and metabolic dynamics during the traditional fermentation of Hongqu aged vinegar, and explore the core functional microbes closely related to the formation of flavor components. Microbiome analysis demonstrated that Lactobacillus, Acetobacter, Bacillus, Enterobacter, Lactococcus, Leuconostoc and Weissella were the predominant bacterial genera, while Aspergillus piperis, Aspergillus oryzae, Monascus purpureus, Candida athensensis, C. xylopsoci, Penicillium ochrosalmoneum and Simplicillium aogashimaense were the predominant fungal species. Correlation analysis revealed that Acetobacter was positively correlated with the production of tetramethylpyrazine, acetoin and acetic acid, Lactococcus showed positive correlation with the production of 2-nonanone, 2-heptanone, ethyl caprylate, ethyl caprate, 1-hexanol, 1-octanol and 1-octen-3-ol, C. xylopsoci and C. rugosa 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 ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry. A variety of amino acids and functional dipeptides were identified during the traditional brewing of Hongqu aged vinegar. Correlation analysis revealed that Lactobacillus 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 Hongqu aged vinegar.