Daqu microbiota adaptability to altered temperature determines the formation of characteristic compounds

Temperature plays a critical role in the performance of microbial communities during traditional solid-state fermentation. However, it remains unknown how temperature shapes microbiota, metabolism, and their relationship in Daqu fermentation. Here, we investigated the response of Daqu microbiota and metabolites to temperature by actual Daqu fermentation and simulated fermentation. First, volatile organic compounds were similar in both fermentation systems. Seventy-nine shared volatile compounds accounted for 94.5 %-96.5 % in Daqu fermentation and 66 %-95.6 % in the end of simulated fermentation, indicating that the formation of compounds in Daqu fermentation could be repeated effectively by simulated fermentation. The simulated fermentation showed the temperature gradient of 17 °C-60 °C significantly affected the formation and accumulation of volatile compounds. Aldehydes, acids, and pyrazines positively correlated with temperature (p < 0.05). Eight compounds were identified as characteristic compounds in high temperature (50-60 °C), including tetramethylpyrazine, trimethylpyrazine, 2,3-dimethyl-5-ethylpyrazine, 3-hydroxy-2-butanone, 2,3-dimethylpyrazine, benzaldehyde, acetic acid, and isovaleric acid. Next, we explored the force of temperature on microbial assembly and microbial interaction in simulated fermentation. Temperature significantly affected the composition of bacterial community (ANOISM, R = 0.779, P = 0.001) and fungi community (ANOISM, R = 0.664, P = 0.001). At the genus level, Weissella, Lactobacillus, Pediococcus, Saccharomycopsis Saccharomyces and Monascus dominated in 17-40 °C while Bacillus, Kroppenstedtia, Oceanobacillus, Lentibacillus, Rasamsonia, Thermoascus, Candida and Aspergillus were predominant genera in 50-60 °C. The succession of Bacillales, Lactobacillales, Eurotiales and Saccharomycetales adapted to changes in temperature. High temperature promoted microbial network complexity and a significant variation in microbial interactions. Furthermore, Procrustes analysis revealed a significant correlation between microbial community and volatile compounds (M2 = 0.6035, P < 0.001). Bacillus, Lentibacillus, Kroppenstedtia, and Oceanobacillus were significant contributors correlated to characteristic compounds. This study revealed the temperature-driven Daqu microbiota functioned as a critical contributor to promoting flavor formation and provided the theoretical basis for regulating fermentation in spontaneous fermentation systems.