Differential characterization of medium-temperature Daqu from different geographical regions: bacterial profile, color, taste, and flavor.

In this study, the sensory qualities of MTD from different geographical regions were comprehensively analyzed using electronic sensing technology. Moreover, the culturable Bacillus species, LAB, and other bacterial communities in these MTD samples were identified using culture methods and single-molecule real-time sequencing. The most abundant culturable species of Bacillus and LAB in MTD were Bacillus licheniformis and Pediococcus pentosaceus, respectively. The bacterial diversity was higher in MTD from the Nanyang region than in that from the Luzhou region, and its sensory quality were superior. Nevertheless, Nanyang MTD showed poorer microecological stability. Functional characterization revealed that the bacterial communities present in MTD were actively enriched in processes related to ribosome structure and biogenesis, as well as cell wall/membrane/envelope biogenesis. Notably, Thermoactinomyces daqus and Leuconostoc citreum emerged as the bacterial species with the highest relative abundance in MTD from the Luzhou and Nanyang regions, respectively, and were identified as biomarkers for the MTD from these two regions. Leuconostoc citreum, Leuconostoc mesenteroides, Pediococcus pentosaceus, Thermoactinomyces daqus, and Weissella paramesenteroides was significantly correlated with the synthesis of aromatic compounds (P < 0.05). These findings expand our knowledge of the microbiological composition and quality of MTD from various regions, offering a valuable reference for product optimization.