## 3 Results and Discussion
### Succession of Microbial Communities and Microbial Interactions
The above results show that sample 3 realized the combination of functional microorganisms for Baijiu fermentation, and that sample 4 had obvious advantages in the production and stability of flavor compounds. Therefore, in order to clearly analyze microbial interactions, we established co-occurrence networks among all the dominant microorganisms with significant interactions for three fermentation systems of the experimental group (Figure 6). We explained the characteristics of microbial interactions in different fermentation systems, so as to provide a basis for analyzing the complex interactions in the fermentation of Baijiu. According to co-occurrence networks of microbial communities in each sample group (Figure 6a-c), we concluded that the positive interactions between microbial genera dominate over negative interactions, and the positive interactions mainly occurred between genera that were beneficial to fermentation. In sample 2, for the six genera (two bacterial genera _Lactobacillus_ and _Clostridium sensu stricto_ 1, and four fungal genera _Wickerhamomyces_, _Rasamsonia_, _Thermoascus_, and _Saccharomyces_), there were significant positive interactions between _Lactobacillus_ and the other five microbial genera, and the remaining genera had significant positive interactions with the two adjacent microbial genera (Figure 6a). In addition, _Ochroductrum_ showed significant positive interactions with _Acinetobacter_ and _Achromobacter_, and significant positive interactions were formed between _Clostridium sensu strictto_ 11 and _Sporolactobacillus_. In sample 3, there was a large interaction network formed by seven bacterial genera (_Pedicoccus_, _Burkholderia_, _Weissella_, _Lactococcus_, _Bacillus_, _Lactobacillus_, and _Clostridium sensu stricto_ 12) and two fungal genera (_A Aspergillus_ and _Saccharomyces_). Among which, there were five positive interactions in the three genera of _Lactobacillus_, _Weissella_, and _Lactococcus_, while the fungal genus _Saccharomyces_ showed significant positive interactions with four bacterial genera, including _Lactobacillus_, _Weissella_, _Lactococcus_, and _Clostridium sensu stricto_ 12 (Figure 6b). Meanwhile, _Clostridium sensu stricto_ 1, _Enterobacter_, and _Sporolactobacillus_ formed a stable positive interaction among the three bacterial genera, and _Klebsiella_ also showed a positive interaction with _Clostridium sensu stricto_ 1. In sample 4 (Figure 6c), a stable positive interaction was formed among _Clostridium sensu stricto_ 1, _Clostridium sensu stricto_ 12, and _Klebsiella_, and the relationships between _Lactococcus_, _Weissella_ and _Burkholderia_ were similar. _Clostridium sensu stricto_ 11 and _Capriciproducens_, _Lactobacillus_ and _Sporolactobacillus_ also showed positive interactions. As for fungal interactions in sample 4, _Saccharomyces_ showed significant positive interactions with _Thermoscus_ and _Wickerhamomyces_, and _Wallemia_ also showed a positive interaction with _Thermomyces_. In addition, there were a few negative interactions in all of the fermentation systems. In sample 2, _unidentified_ (Fungi) showed negative interactions with four microbial genera (_Enterobacter_, _Kosakonia_, _Klebsiella_ and _Isatchenkia_) (Figure 6a). In sample 4, there was a negative correlation between _unidentified_ (Fungi) and _Saccharomyces_, and the genus _Rasamsonia_ and three bacterial genera (_Lactococcus_, _Weissella_ and _Saccharomyces_) (Figure 6c). In sample 3, _Bacillus_, which has an adverse effect on fermentation, formed significant negative interactions with other genera (_Pediococcus_, _Weissella_, _Lactococcus_, _Lactobacillus_, _Clostridium sensu stricto_ 12, _Apergillus_, and _Saccharomyces_) (Figure 6b). It is worth noting that _Apergillus_ formed negative correlations with _Weissella_, _Bacillus_, _Lactobacillus_ and _Clostridium sensu stricto_ 12, which might be attributed to the extremely high abundance of _Apergillus_ on day 0 of fermentation in sample 3, and the abundance decreasing in the middle and late stages of fermentation.