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Polygonum hydropiper (PH) is a rich source of active compounds and serves as a pivotal ingredient in Chinese rice wine (Huangjiu) production. This study investigates the impact of PH and Polygonum hydropiper extract (PHE) on ethyl carbamate (EC) production during Huangjiu fermentation. Our findings reveal that PH enhances the relative abundance of Bacillus subtilis in Huangjiu fermentation, thereby facilitating its interaction with Saccharomyces cerevisiae. Furthermore, PH modulates the urea metabolism of S. cerevisiae. In the PH- B. subtilis-S. cerevisiae fermentation system, the expression of DUR1,2 and DUR3 genes in S. cerevisiae is upregulated. This augmentation leads to increased urea uptake and metabolism by S. cerevisiae in the fermentation broth, subsequently reducing the urea concentration in the fermentation medium (The EC content in the CK group was approximately 355.55 % and 356.05 % higher than those in the PH and PHE groups, respectively). Consequently, PH demonstrates promise in reducing the EC concentration of Huangjiu, offering a novel approach to enhance the safety of Huangjiu consumption. [Display omitted] • Regulation of PH and PHE reduces urea and ethyl carbamate content. • Significant impact on Bacillus subtilis abundance. • Enhanced microbial interactions. • Upregulation of urea utilization pathways. [ABSTRACT FROM AUTHOR]

Aromatic alcohols (including β-phenylethanol, tyrosol and tryptophol) could contribute positively to the aroma flavor of huangjiu at an appropriate amount. In this study, it was found that the aromatic alcohols in huangjiu were predominantly synthesized by Saccharomyces cerevisiae HJ01. The Ehrlich pathway and shikimate pathway, including 31 genes, are responsible for aromatic alcohol biosynthesis in S. cerevisiae. During the first 120 h of huangjiu fermentation, the genes GAP1 HJ01 (permease), BAT2 HJ01 (transaminase), PDC1 HJ01 and PDC5 HJ01 (pyruvate decarboxylase), and ADH1 HJ01 (alcohol dehydrogenase) formed integrated Ehrlich pathway are responsible for aromatic alcohol biosynthesis. In S. cerevisiae HJ01, the mutations in the promoter region of genes GAP1 HJ01, BAT2 HJ01, PDC1 HJ01, and PDC5 HJ01 involved in the Ehrlich pathway increased the promoter strength and transcriptional levels of related genes. The addition of 20 U/g acid protease could substantially increase the expression levels of genes involved in the Ehrlich pathway, and therefore there were 34.7% increasing for the concentration of total aromatic alcohols. • Aromatic alcohols in huangjiu are synthesized by Saccharomyces cerevisiae. • Aromatic alcohols in huangjiu are mainly synthesized through the Ehrlich pathway. • Key genes and promoter mutations in Ehrlich pathway were identified. • Acid protease enhanced expression level of key genes. [ABSTRACT FROM AUTHOR]