Effect of Saccharomyces cerevisiae inoculation on the co-fermentation of Clostridium kluyveri and Clostridium tyrobutyricum: A strategy for controlling acidity and enhancing aroma in strong-flavor Baijiu

Abstract

Microbial synergistic fermentation plays a vital role in the intelligent brewing and industrial upgrading of the Chinese traditional Baijiu fermentation industry. In this study, a chain-elongating microbial assemblages consisting of Clostridium and varying proportions of S. cerevisiae was applied to a solid-state simulated fermentation system to validate its functionality during strong-flavor Baijiu fermentation. The addition of S. cerevisiae promoted the hydrolysis of fermented grains and reduced the acidity compared with Clostridium biofortification (Group CFE; P < 0.05). The most significant enhancement in volatile flavor substances was achieved by the addition of S. cerevisiae at a high proportion (Group SFB), where the yields of ethyl hexanoate, phenylethyl alcohol, and ethanol increased by 191.2 %, 109.8 %, and 59.7 %, respectively. The OPLS-DA model (R²X = 0.976, Q² = 0.992) identified seven volatile flavor substances that effectively distinguished the different co-fermented grains (VIP > 1, P < 0.05). S. cerevisiae accelerated the enrichment of Lentilactobacillus, Lactiplantibacillus, Loigolactobacillus, and Clostridium_sensu_stricto_12. Metabolic pathway and correlation analysis revealed that S. cerevisiae provides endogenous ethanol to chain-elongating microorganisms, and this fungal-bacterial synergistic fermentation enhances the reverse β-oxidation pathway, ultimately contributing to the production of volatile flavor substances. Overall, the microbial assembly pattern of chain-elongating microbial assemblages will help achieve quality enhancement and intelligent control by increasing the production of flavor ethyl esters and ethanol for Baijiu solid-state fermentation system.