Synthetic and natural microbial communities in high-temperature Daqu production: Insights into metabolic pathways and volatile organic compounds

Abstract

High-temperature Daqu (HTD), an essential fermentation starter in sauce-aroma Baijiu, is characterized by complex microbial communities that vary significantly across production regions. Traditional HTD production faces challenges in consistency and quality control, hindering industrial scalability. This study compared 54 synthetic microbial communities (SynMC)-fortified HTD samples with 39 traditional HTD samples from core production regions, which are Renhuai, Luzhou, and Jinsha, respectively, to elucidate their microbial and metabolic profiles. Physicochemical analysis revealed high similarity between fortified and traditional samples, while organic acid profiling demonstrated distinct regional patterns. Volatile organic compound (VOC) analysis identified 190 characteristic components across regional samples, with phenols and pyrazines dominating in Renhuai HTD, ketones in Luzhou samples, and esters in Jinsha HTD. Notably, certain SynMC samples (A14, A25, A13, and A34) closely replicated the VOC profiles of traditional HTD. Microbial community analysis revealed region-specific fungal and bacterial signatures, with SynMC samples successfully mimicking these patterns. Dominant fungi included Thermomyces, Thermoascus, and Monascus, while bacterial communities featured Kroppenstedtia, Thermoactinomyces, and Bacillus. Metabolic pathway analysis identified 72 shared pathways between corresponding SynMC and traditional HTD groups, including those involved in amino acid biosynthesis, central carbon metabolism, and energy production. Moreover, the study emphasizes the pivotal role of Bacillus as a key microorganism in driving metabolic function. These findings provide theoretical insights and practical strategies for optimizing HTD stability through SynMC technology, potentially enabling more efficient large-scale production while preserving the traditional flavor characteristics of sauce-aroma Baijiu.