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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 Baijiu produced by the HT group had a better overall performance. The Baijiu in the HT group exhibited higher quality in terms of sweetness, fruity and floral, whereas the Baijiu in 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 Baijiu flavors 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 Baijiu driven by different temperatures. These results provide solid data support for optimizing the Baijiu fermentation process under different seasonal temperatures. [Display omitted] • The complexity of the microbial ecological network was increased in the HT. • The sensory attributes of Baijiu in the HT group exhibited superior overall quality. • 24 compounds were found that could distinguish between two temperatures of Baijiu. • Revealed the correlation between microorganism and flavor at different environmental temperatures. [ABSTRACT FROM AUTHOR]

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 farinosa on strong-flavor Daqu was discussed. The results indicated a significant decrease in Bacillus and an increase in five bacterial genera (e.g., Weissella and Staphylococcus) and four fungal genera (e.g., Saccharomycopsis and 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 Staphylococcus in 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. [Display omitted] • Microbiota can be regulated by bioaugmentation under controlled process parameters. • Acid and bio-heat produced by microbes could promote the microbiota shift. • Microbial community succession was promoted by bioaugmentation inoculation. • Bioaugmentation inoculation enhanced the content of esters and aromatic compounds in Daqu. [ABSTRACT FROM AUTHOR]