## 3 Results and Discussion
### Correlation of Microbial Community with Volatile Flavor Compounds  
Based on the Spearman correlation coefficient, correlation clustering heatmaps and correlation network diagrams were used to reveal the potential correlations between dominant microbial communities and 22 key volatile flavor compounds with \(p<0.05\) and VIP \(>1\), aiming to capture the core microbial community in the salt-reduced fermentation. The results showed that the 20 dominant microbial genera could be classified into five categories, A, B, C, D, and E, while the 22 key volatile flavor compounds could be classified into six categories, F, G, H, I, J, and K (Figure 8a). The microbial genera of class B were significantly negatively correlated with isobutanol (V17) and 1-naphthalenol (V19) in class F flavor compounds, but significantly positively correlated with the flavor compounds of class J; microbial genera of class C showed a significant positive correlation with the flavor compounds of classes I and J; however, _Enterobacter_ (M2) in this group exhibited a significant negative correlation with the flavor compounds of class G; the microbial genera of class D were significantly negatively correlated with the flavor compounds of class J and K, but showed a significant positive correlation with isobutanol (V17); microbial genera of class E were significantly positively correlated with flavor compounds of classes G and K (Figure 8a). Furthermore, according to the correlation network diagram, 16 dominant microbial genera were significantly correlated with 17 key volatile flavor compounds (\(p<0.01\), \(|\)\(\varrho\)\(|>0.6\)) (Figure 8b). Among them, _Wickerhamomyces_ (M19), _Bacillus_ (M1), _Staphylococcus_ (M4), and _Mortierella_ (M12) all showed highly significant positive correlations with \(\geq\)3 volatile flavor compounds. They may play crucial roles in forming characteristic flavors in different salt concentrations of BBP-meju [62]. These results agreed with the high-throughput sequencing results, again emphasizing the importance of _Bacillus_, _Staphylococcus_, and _Mortierella_. _Wickerhamomyces_ (M19) is a dominant fungal community in traditional fermented foods, such as kimchi, sour pork, and sourdough. It can secrete proteases that hydrolyze proteins in raw materials into peptides and amino acids, further converting them into various flavor compounds. Therefore, _Wickerhamomyces_ (M19) can impart freshness to the products and coordinate the overall aroma characteristics of fermented foods [63; 64]. Research by [PERSON] et al. [65] indicated that _Wickerhamomyces_ (M19) was positively correlated with esters such as ethyl acetate, heptadecanoic acid ethyl ester, ethyl triccanoate, and decanoic acid ethyl ester, especially a high-quality producer of ethyl acetate [66]. In this study, _Wickerhamomyces_ (M19) showed significantly positive correlations with ethyl acetate (V6), pentyl acetate (V7), 1-nonanol (V10), 3-methyllhiopropanol (V14), 2,3-butanediol (V15), glycerol (V16), and 1-naphthalenol (V19). However, it negatively correlated significantly with crotonaldehyde (V2) (Figure 8b). Meanwhile, the relative abundance of _Wickerhamomyces_ (M19) increased gradually during fermentation, with the highest abundance in medium-salt meju and the lowest in low-salt meju (Figure 8b). It is known that _Wickerhamomyces_ (M19) has a good tolerance to high osmotic pressure [67]. Therefore, the high abundance of _Wickerhamomyces_ (M19) in medium-salt meju contributed to the accumulation of fruity, sweet, and other quality flavors and attenuated the harsh flavors caused by crotonaldehyde (V2). Apart from _Wickerhamomyces_ (M19), _Staphylococcus_ (M4) and _Weissella_ (M10) were significantly positively correlated with ethyl acetate (V6) and pentyl acetate (V7) (Figure 8b). This suggested a synergistic effect among _Wickerhamomyces_ (M19), _Staphylococcus_ (M4), and _Weissella_ (M10), collectively promoting the formation of ester flavors.