Unraveling the metabolic network of organic acids in solid-state fermentation of Chinese cereal vinegar

Shanxi aged vinegar (SAV) is fermented by multispecies microorganism with solid-state fermentation (SSF) technology, which contains a variety of organic acids. However, the metabolic network of them in SSF is still unclear. In this study, metagenomics technology was used to reveal the microbial community and functional genes in SAV fermentation. The metabolic network of key organic acids with taste active value higher than 1 was reconstructed for the first time, including acetate, lactate, malate, citrate, succinate, and tartrate. The results show pyruvate is the core compound in the metabolic network of organic acids. Metabolic pathway of acetate plays a pivotal role in this network, and acetate has regulatory function on metabolism of other organic acids. Acetobacter and Lactobacillus are the predominant genera for organic acid metabolism in SSF of SAV. This is also the first report on metabolic network of organic acids in cereal vinegar, adding new knowledge on the flavor substance metabolism during multispecies fermentation of traditional fermented food.