## 4 Discussion
In this research, the composition of the fungal microbial community was markedly lower than the bacterial microbial community, which was mostly due to the thermolabile yeast-tand themold were eliminated when the fermentation temperature increased during the manufacturing process of high-temperature _Daqu_[16; 17]. The _Bacillus_ and _Aspergillus_ genera were the most abundant in the BQ sample (Figure 3b,d). However, in the study of southern Chinese high-temperature _Daqu_, the predominant genus of WQ was _Bacillus_[48]. _Bacillus_ and _Aspergillus_ were the main microbial genera in various types of _Daqu_, which could produce a variety of flavor precursors and substances; especially important are contributions to the production of pyrazines [15; 53; 54]. Interestingly, the correlational heatmap analysis showed that _Bacillus_ and _Aspergillus_ had no significant correlation with tetramethylpyrazine. The result suggested that the driving force for the increase in the tetramethylpyrazine concentration in _Daqu_ was not microorganisms but was possibly influenced instead by temperature and other environmental factors [55]. Previous studies have identified _Byssochlamys_ as a dominant fungal genus in high-temperature _Daqu_, and _Byssochlamys_ could degrade starch in raw materials [35]. The relative abundance of _Byssochlamys_ was significantly higher in BQ than in WQ and YQ (Figure 3d), and the abundance of _Byssochramys_spectabilis_ was also the highest (Figure 5 4a), which may be owing to the higher fermentation temperature of BQ. In this study, the RDA analysis also showed that _Aspergillus_ and _Byssochlamys_ were significantly positively correlated with saccharifying and fermenting powers (Figure 5). _Oceanobacillus_ promotes the production of esterase and amylase [25], which was the dominant bacteria genus in YQ and BQ, and relative abundance was higher in YQ than in BQ (Figure 3c). [PERSON] et al. found that _Oceanobacillus_ was a dominant bacteria in sauce-flavored baijiu fermentation [21], along with Luzhou-flavored baijiu and Fen-type fermented grains [52; 56]. [PERSON] et al. showed that _Oceanobacillus_ was the dominant genus in the WQ type of southern high-temperature _Daqu_, while the abundance of _Oceanobacillus_ in WQ in this study was less than 1% [27]. Figure 6 showed that _Oceanobacillus_ and _Byssochlamys_ were positively correlated with some esters, alcohols, acids, and tetramethylpyrazine. Many studies have identified _Thermoascus_ and _Thermoascus_ as dominant fungi in different _Daqu_ samples [48; 57]. _Thermoascus_ could produce various enzymes and have a crucial impact on the formation of high-temperature _Daqu_[58]. However, the correlation between _Thermoomyces_ and flavor was completely opposite to that of _Byssochlamys_; it was positively correlated with pyrazines instead (Figure 6). _Byssochlamys_, _Thermoascus_, and _Thermoys_ belong to thermostable microorganisms, which have high abundance in YQ and BQ. _Scopulibacillus_ and _Kroppenstedtia_ had the highest relative abundance in WQ (Figure 3b). The RDA analysis showed that _Scopulibacillus_ demonstrated a huge positive connection with starch (Figure 5), and starch was the highest in WQ; the results were consistent. However, the correlational analysis showed that _Kroppenstedtia_ had no significant correlation with the physicochemical indexes and volatile flavor components (Figures 5 and 6). [PERSON] et al. also demonstrated that _Scopulibacillus_ and _Kroppenstedtia_ were predominant genera in northern Jiang-favored _Daqu_. However, little research has been conducted on their biological functions [59]. _Kroppenstedtia_ belongs to the _Thermoactinomyces_ family, and many studies have found that it is a dominant bacteria in different _Daqu_ samples [52]. In the late phase of fermentation of _Daqu_, _Kroppenstedtia_, _Bacillus_, and _Scopulibacillus_ significantly increased [55]. _Virgibacillus_ had the highest abundance in YQ. [PERSON] et al.