Yeast community in the first-round fermentation of sauce-flavor Baijiu: Source, succession and metabolic function

Yeasts play a crucial role in determining the quality and yield of sauce-flavor Baijiu, yet the source, succession, and metabolic functions of the yeast community in fermented grains during stacking fermentation remains unclear. In this study, amplicon sequencing combined with solid-state fermentation was used to investigate the structure and function of yeast community during the first-round fermentation of sauce-flavor Baijiu. The richness and diversity of yeast community increased throughout fermentation, with 83.05 % of yeast ASV sourced from the fermentation environment. Fourteen yeast genera were identified, with Wickerhamomyces (29.6 %), Saccharomycopsis (25.0 %), and Torulaspora (14.9 %) being the predominant genera. These genera showed distinct spatial distributions throughout the fermentation stack. Spearman correlation analysis indicated positive correlations between the three genera and multiple volatiles in fermented grains alcohols and esters. After solid-state fermentation in pure culture, T. delbrueckii ME22, S. fibuligera ME8, and W. anomalus ME57 produced distinct floral, fruity, and sweet flavor compounds, such as phenylethyl alcohol, isoamyl alcohol, ethyl acetate, phenethyl acetate, and isoamyl acetate. T. delbrueckii ME22 demonstrated a great capacity for cellulose degradation, whereas S. fibuligera ME8 exhibited enhanced capabilities for protein and starch degradation. This study provides a theoretical reference for the application of yeast in the fermentation of sauce-flavor Baijiu.