## 3 Results and Discussion
### Correlation Analysis of Flavor Compounds and Microorganisms
In addition, it is worth noting that in sample 4, flavor compounds b1 (phenylethyll alcohol), b3 (3-methyl-1-butanol), a18 (decanoic acid, ethyl ester), a20 (hexanoic acid, ethyl ester), a19 (hexanoic acid, butyl ester), a26 (octanoic acid, ethyl ester), h1 (benzaldehyde), a10 (gamma-nonanolactone), and f1 (2-heptanone) were positively correlated with most of the major bacterial genera such as _Clostridium sensu stricto_ 12, _Klebsiella, Kosakonia, Clostridium sensu stricto_ 1, _Enterobacter_, _Weissella, Lactococcus_, and _Burkholderia_ (Figure 7c). The negative correlations were mainly concentrated on _Acinetobacter_, _Achromobacter_, _Orthochatrum_, _Fictibacillus_, and _Bacillus_ with flavor compounds a14 (butanoic acid, ethyl ester), a12 (butanediolic acid, diethyl ester), a21 (lactic acid, ethyl ester), c2 (2-methoxy-4-methylphenol), a10 (gamma-nonanolactone), a1 ((Z)-ethyl heptadec-9-enoate), a22 (heptadecanoic acid, ethyl ester), a13 (butanoic acid, butyl ester), a2 ((Z)-ethyl pentadec-9-enoate), and e1 (butanoic acid) in sample 2, while in sample 3, only _Acinetobacter_ displayed significant negative effects on several flavor compounds. In sample 4, _Acinetobacter_, _Fictibacillus_, and _Bacillus_ showed negative effects on flavor compounds, but the negative correlations were not as obvious as those in sample 2. This confirmed that using the combination of functional microorganisms to replace part of the Daqu, could weaken the adverse effects of the Daqu microorganisms on the production of flavor compounds in the fermentation process, and promote the stable production of flavor compounds (Figure 7c). A correlation analysis between the fungal microorganisms and flavor compounds showed that the contribution of fungi to flavor compounds was significantly less than that of bacteria (Figure 8a-c). In sample 2, _Byssochlamys_ and _Isatchenkia_ showed significantly positive correlations with most flavor compounds, and _Saccharomyces_, _Thermoascus_, _Wickerhamomyces_, and _Rasamsonia_ showed positive correlations with most flavor compounds (Figure 8a). In sample 3, _Aspergillus_ showed significantly positive effects on most flavor compounds, while _Cladosporium_ and _Saccharomyces_ showed significant positive effects on some flavor compounds (Figure 8b). In sample 4, _Aspergillus_ also showed significantly positive effects on most of the flavor compounds, and _Cladosporium_, _Saccharomyces_, and _Trichosporon_ showed significantly positive effects on some flavor compounds (Figure 8c). The results indicate that microorganisms common to sample 3 and sample 4 were positively associated with flavor compounds, but were different from those in sample 2. In sample 3 and sample 4, _Aspergillus_ and _Saccharomyces_ were strongly positively associated with the production of flavor compounds. _Aspergillus_ was the predominant fungal genus in sample 2, and displayed positive correlations with most flavor compounds but the correlation was not obvious, while in sample 3, _Aspergillus_ showed significantly positive effects on most flavor compounds (seventeen esters, two alcohols, one phenol, one alkane, one furan, one