Revealing the protein dynamics of low-temperature Daqu during Daqu-making process by metaproteomics, enzyme activity assay, and ELISA

This study aimed to elucidate the protein profiles of low-temperature Daqu during the Daqu-making process. Temporal metaproteomics was conducted across 8 stages of Daqu production. The top 50 proteins in Daqu were primarily derived from peas, the diversity and abundance of microbial-source proteins increased significantly from the Liangmei stage. The marker microbial proteins at different Daqu-making stages were screened via random forest analysis. Chaperonin GroEL from Lactiplantibacillus plantarum and Enolase from Lactobacillus acidophilus were identified as markers during Liangmei and Chaohuo stages. Additionally, the enzyme activities of hydrolases and oxidoreductases were analyzed, suggesting that the activities of acid protease, polygalacturonase, and carboxyl esterase significantly improved after the Liangmei stage. Notably, ELISA (enzyme-linked immunosorbent assay) for superoxide dismutase and α-galactosidase was first applied to the biochemical analysis of low-temperature Daqu, and verified its reliability and applicability. This study was conducive to understanding the protein dynamics during Daqu-making, and provided insights for evaluating the quality of Daqu.