Microbial metabolism during the thermophilic phase promotes the generation of aroma substances in nongxiangxing Daqu.

ABSTRACT

The thermophilic phase of Daqu fermentation is considered the key period for aroma production in Daqu, but little is known about the changes in substances during this phase. In this study, we combined a metabolomics approach with high-throughput sequencing to analyze the metabolic profiles and identify metabolism-associated microbes during the thermophilic phase of Daqu fermentation. The results revealed that the metabolic sets after 5 and 9 days of fermentation in the thermophilic phase were similar, and several amino acid and biosynthesis-related metabolic pathways were significantly enriched. In addition, pyrazines and alkanes increased and esters decreased significantly after the thermophilic phase. The metabolism of substances during the thermophilic phase involved 38 genera, and the main metabolic pathways involved were glycolysis, TCA cycle, butyric acid metabolism, and five amino acid metabolic pathways. In summary, this study points in the direction for unravelling the mechanism of aroma production in Daqu.