The dynamics of microbial community and flavor metabolites during the acetic acid fermentation of Hongqu aromatic vinegar

In this study, we investigated the dynamics of microbial community and flavor metabolites during the traditional fermentation of Hongqu aromatic vinegar (HAV) and subsequently explored the potential relationship between microbiota and flavor metabolites. The microbiome analysis based on high-throughput sequencing (HTS) of amplicons demonstrated that Lactobacillus, Acetobacter and Clostridium were the dominant bacterial genera, while Alternaria, Candida, Aspergillus and Issatchenkia were the dominant fungal genera during the acetic acid fermentation (AAF) of HAV. A total of 101 volatile flavor compounds were identified through gas chromatography-mass spectrometry (GC-MS) during HAV fermentation, including esters (35), alcohols (17), aldehydes (11), acids (11), ketones (7), phenols (10), and others (10). Redundancy analysis (RDA) was used to reveal the correlation between microbiota and volatile flavor compounds. Lactobacillus and Acetobacter were the two bacterial genera that have the great influence on the production of volatile flavor components in HAV. Among them, Lactobacillus was positively correlated with a variety of ethyl esters, while Acetobacter positively contributed to the formation of several organic acids. Furthermore, the non-volatile metabolites were detected by ultra-high-performance liquid chromatography with quadrupole time-of-flight mass spectrometry (UPLC-QTOF/MS). A total of 41 dipeptides were identified during HAV fermentation, and most of them may have sensory characteristics and biological activities. RDA showed that Aspergillus, Epicoccum, Issatchenkia, Candida and Malassezia were the most influential fungal genera on non-volatile metabolites. In particular, Epicoccum was first reported in Hongqu vinegar and showed a positive correlation with the production of various organic acids. In conclusion, this study provides a scientific basis for understanding the flavor generation mechanism of HAV, and may be valuable for developing effective techniques to select suitable strains to improve the flavor quality of HAV.

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Microbial community in Hongqu aromatic vinegar was investigated by high-throughput sequencing.

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The key flavor metabolites during the acetic acid fermentation of HAV were selected through PLS-DA.

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Lactobacillus, Acetobacter and Clostridium were the predominant bacterial genera in HAV fermentation.

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Alternaria, Candida, Aspergillus and Issatchenkia were the predominant fungal genera in HAV fermentation.

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Redundancy analysis (RDA) revealed the correlation between microbiota and flavor metabolites.