Moisture transfer drives synergistic effects of microbial adaptation and functional enzyme metabolism in Daqu solid-state fermentation

In this study, we employed a semi-closed intelligent temperature and humidity control platform developed independently, combining low-field nuclear magnetic resonance (LF-NMR) with metagenomic sequencing to comprehensively investigate the key physicochemical factors responding to moisture transfer, microbial adaptability and the metabolic distribution characteristics of functional enzymes. Specifically, the study first identified the key physicochemical parameters of the Daqu porous structure under different initial moisture content gradients, and elucidated the preferential effect of moisture transfer energy. We further quantified the mass transfer rates and accelerations of different types of moisture, revealing the spontaneous adsorption-desorption behavior. Ultimately, we explored the structure of microbial communities, substrate nutrient metabolic pathways, and the expression of saccharification-function enzyme genes driven by moisture transfer, and established mathematical relationships between moisture transfer kinetics and microbial metabolism under various dynamic conditions. In summary, our research indicated that moisture transfer regulated the differentiation and metabolic levels of saccharification functions by driving substrate structure, nutrient availability, and microbial adaptability.