Effects of environmental factors on the microbial community changes during medium-high temperature Daqu manufacturing.

Environmental factors and microbial interaction influence the changes in microbial community and enzyme profiles during different stages of medium-high temperature Daqu manufacturing. In this study, the specific changes in microbial community and environmental factors at various stages of Daqu production were comprehensively analyzed using a combination of environmental factor analysis and high-throughput sequencing technology. Further, the effects of environmental factors and microbial interaction on microbial succession were investigated via correlation analysis; the enzymes related to saccharification and ethanol fermentation during Daqu production were explored. The study revealed that the whole process of Daqu production was divided into three stages based on temperature. Fungal were active in the early stage, while bacteria were more active in the middle to later stages. Bacillus, Weissella, Thermoactinomyces and Lactobacillus were the main bacterial genera, while Thermoascus, Thermomyces, Kodamaea, and Aspergillus were the dominant fungi. The effects of ambient humidity, CO2. and moisture on the microbial community were significant, and these environmental factors positively correlated with most fungi, but negatively correlated with Thermoactinomyces, Saccharopolyspora, and Acinetobacter. In addition, the enzymes encoded by fungi, related to saccharification and ethanol fermentation, might be consistent with the high abundance of Thermoascus and Thermomyces. Meanwhile, enzymes encoded by bacteria could mainly originate from Weissella.