## 3 Results and Discussion
### Correlations between Core Functional Microbial Community and Characteristic Flavor Compounds  
It is widely accepted that the rice wine aroma has a significant influence on its sensory quality and consumer preferences [32]. The aromatic variations are mainly due to the raw materials, fermentation agents, and the fermentation and aging processes [15]. Nevertheless, in this research, the different flavor of the BRW was mainly caused by the diverse microbial compositions in starters. To explore the core functional microbial communities in the brewing process of BRW, the O2 PLS model, based on variable importance in projection, was used to analyze the impact of microbial communities (20 top fungi and 50 top bacteria) on the formation of all volatile flavor compounds in all BRWs. The O2 PLS method was appropriate for analysis and prediction, as demonstrated by the R\({}^{2}\) and Q\({}^{2}\) values, which were close to 1.0 and greater than 0.5, respectively [33]. There were 15, 26, and 23 genera, respectively, which had a significant influence on flavor substances in Q1, Q2 and Q3 (VIP \(>\) 1.0, \(p<\) 0.05) (Figure 4a-c and Table S5). While it is understood that certain strains played a major role in the development of volatile compounds in the BRW, it is yet to be determined which strains were beneficial for the formation of the wine's characteristic flavor compounds, and which were negative. The Spearman's correlation between the microbial community (20 top fungi and 50 top bacteria) and the 18 characteristic flavor substances of the BRW was calculated and then visualized using Cytoscape software, see Figure 4d-f. (\(\left|\,\mathrm{r}\right|>0.6\), \(p<\) 0.05). It is observed that the dominant _Saccharomyces_ in the samples from Sichuan Dazhu and Hubei Fangxian had a significant negative correlation with 16 and 15 characteristic flavor substances, respectively. Similarly, the high abundance fungi in the Jiangxi Yingtan sample, such as unclassified_f_Metschnikowiaceae and _Clavispora_, evinced a significant negative correlation with 16 characteristic flavor substances. On the basis of the prior analysis, it is speculated that the main function of these microbes is to decompose macromolecular substances and supply the necessary precursors for microorganisms that generate flavor. The presence of other fungi, including abnormal _Wickerhamomyces_ and _Saccharomyces_ genera, had been found to significantly contribute to the formation of characteristic flavor compounds in three BRWs. Viewed from the perspective of bacterial communities, in the Q1 and Q3 samples _Pedicoccus_ was significantly positively correlated with the characteristic flavor compounds, whereas _Achromobacter_, _Pantoea_ and _Acinetobacter_, being low-abundance bacterial genera, displayed a negative correlation. A strong positive correlation was observed between lactic acid bacteria (_Lactobacillus_, _Weissella_ and _Pediococcus_) and flavor compounds in Q2. An increased number of connections between one microbe and characteristic volatile substances in the network indicates that the microorganism is more vital for the formation of flavor compounds [34]. In addition, functional microorganisms are deemed to have a connectivity of more than 10 with characteristic volatile compounds [23]. Table S6 demonstrates that 11 fungal genera and 3 bacterial genera were selected as the functional microorganisms that produced characteristic volatile flavors, indicating that fungi were more influential in the fermentation process, which was consistent with previous research results [34; 35]. Figure 4: _Cont._  
Figure 4: Correlation between microbial genera and volatile flavor compounds.