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Environmental temperature is a crucial factor that affects the fermentation quality of Baijiu. In this study, Illumina Miseq sequencingd, Two-dimensional gas chromatography coupled to mass spectrometry (GC × GC-MS), and physicochemical analyses were employed to investigate the microbial communities, flavor compounds, and physicochemical properties during fermentation at different ambient temperatures (10 ± 2 °C in the lower environmental temperature (LT) group and 22 ± 2 °C in the higher environmental temperature (HT) group). The findings demonstrated an augmentation in microbial diversity, ecological network complexity, and utilization of raw materials by microorganisms in HT group. Sensory analysis showed that sensory properties of Baijiuproduced by the HT group had a better overall performance. The Baijiuin the HT group exhibited higher quality in terms of sweetness, fruity and floral, whereas the Baijiuin the LT group displayed a greater degree of unpleasant pungency and acidity. 24 flavor compounds were identified with the Variable Importance in Projection (VIP) > 1, and they were the main factors contributing to the differences in Baijiuflavors at two environmental temperatures. Correlation analysis showed that ambient temperature influenced microbial interactions and their correlation with metabolites. This difference showed the quality change of Baijiudriven by different temperatures. These results provide solid data support for optimizing the Baijiufermentation process under different seasonal temperatures.

Daqu, an indispensable starter, significantly affects the quality and yield of Chinese baijiu. The microbial community, physicochemical properties, and volatile components of traditional Daqu(TD) and fortified Daqu(FD) were analyzed and compared. The bioturbation effect of inoculation with Bacillus subtilis, Staphylococcus epidermidis,and Millerozyma farinosaon strong-flavor Daquwas discussed. The results indicated a significant decrease in Bacillusand an increase in five bacterial genera (e.g., Weissellaand Staphylococcus) and four fungal genera (e.g., Saccharomycopsisand Millerozyma) after bioaugmentation inoculation. The volatile compound content, including esters and aromatic compounds, increased dramatically after bioaugmentation inoculation. The correlation analysis showed that the Weissella, Pediococcus, and Staphylococcusin FD were positively associated with esterification activity. Moreover, PICRUSt2 predicted many enzymes involved in aroma production and ethanol fermentation. Bioaugmentation inoculation promoted microbial community succession and regulated microbial metabolic activity to enhance the flavor characteristics of Daqu.