## 3 Results and Discussion
### Correlation Analysis Between Volatile Flavors and Communities (Bacterial and Fungi)  
The genera _Bacillus_ and _Pseudomonas_ exhibited a positive correlation with 2-methyl-1-propanol, 3-methyl-1-butanol, and phenylethyl alcohol (Figure 4a). Prior studies have highlighted a significant positive relationship between these genera and certain higher alcohols [14; 51; 52]. These findings suggest that bacteria within these genera may have the capability to produce higher alcohols. Regarding ester compounds, consistent microbial effects were examined between the control and experimental groups. _Enterobacter_ was found to be strongly positively correlated with ethyl acetate, while _Pediococcus_ was negatively correlated with ethyl lactate. _Bacillus_ demonstrated positive correlations with most ester compounds. Notably, diethyl succinate showed significant correlations with both SY and KB, indicating that the _Bacillus_ genus could enhance the production of various ester compounds, particularly those contributing to characteristic flavors during the fermentation process of CFB. Numerous studies have revealed that _Bacillus_ species, like _Bacillus licheniformis_ and _Bacillus velexensis_, can secrete esterases to synthesize ethyl esters from short-chain fatty acids [53; 54]. Such enzymatic activity increases the concentration of esters, including ethyl acetate, ethyl hexanoate, and ethyl butyrate, in baijiu. _Mucor_ exhibited positive correlations with 2-methyl-1-propanol, 3-methyl-1-butanol, and phenylethyl alcohol, with correlation coefficients of 0.608, 0.788, and 0.801, respectively (Figure 4b). Our research revealed that the phenylethyl alcohol content in SY was approximately five times as high as that in KB by the end of fermentation. _Mucor_ has been reported to produce substantial amounts of protease, which converts L-phenylalanine into phenylethyl alcohol [55; 56]. To give an example, high ethanol production by _Mucor_ was considered to be a key characteristic of this strain during fermentation with starch as the substrate--a finding consistent with this study, where _Mucor_ showed a strong correlation with ethanol [57]. Figure 4: Correlations between microorganisms (bacterial (a) and fungal (b)) and volatile flavor substances, with significant differences based on Pearson correlation analysis. The red lines represent positive correlations, the black lines represent negative correlations, and the thickness of the lines indicates the strength of the correlation. Additionally, phenylethyl alcohol, 3-methyl-1-butanol, 2-methyl-1-propanol, and benzyl alcohol all demonstrated strong positive correlations with _Pichia_[58], with correlation coefficients of 0.938, 0.905, 0.858 and 0.847, respectively. _Pichia_ has been reported to enhance the synthesis of higher alcohols, particularly increasing the content of phenylethyl alcohol. Regarding esters, _Pichia_ showed a strong correlation with ethyl lactate, with a coefficient of 0.765. Moreover, this genus also had a strong correlation with higher fatty acid ethyl esters like ethyl oleate, ethyl propionate, ethyl laurate, diethyl succinate, and palmitic acid ethyl ester, with correlation coefficients of 0.99, 0.975, 0.967, 0.95, and 0.937, respectively. Consequently, both _Mucor_ and _Pichia_ were key players in forming characteristic volatile flavors in CFB. Aromatic compounds exhibited fluctuations during the CFB fermentation. The significant positive relationship between microorganisms and aromatic compounds demonstrated the substantial role that microorganisms play in synthesizing these flavor chemicals (Figure 5). Microbial metabolism facilitated by enzymes in associated metabolic pathways [59] essentially involves a dynamic balance between the synthesis and degradation of specific flavor compounds. To better modulate the metabolism of aromatic chemicals through microorganisms in subsequent studies, the metabolic synthesis pathways of these compounds were summarized.