Microbial community, metabolic, and flavor differences among high-temperature Daqu with varying Douchi aroma intensities: a comprehensive metagenomic and metabolomic analysis

The Douchi aroma is widely regarded as a key quality marker of high-quality high-temperature Daqu, but the compounds related to Douchi aroma formation and the key aroma-producing microorganisms remain unclear, which this study seeks to clarify. Therefore, metagenomic and metabolomic approaches were employed to decode the characteristic compounds and core microbial contributors in high-temperature Daqu samples no (NF), light (LF), and strong (SF) Douchi aroma. Esters were the most abundant volatiles across all groups, while acids increased with aroma intensity. <i>Lentibacillus daqui</i>, enriched in SF, showed strong positive correlations with isocetic, phenylacetic, and nonanoic acids. In contrast, <i>Lichtheimia ramosa</i> and <i>Monascus purpureus</i> were dominant in NF and LF, respectively. Furthermore, functional prediction and KEGG analysis further revealed potential biosynthetic pathways for phenylacetic and acetic acid. These findings clarify the molecular and microbial basis of Douchi aroma formation and provide a scientific reference for targeted quality regulation in Daqu production.