## 3 Results and Discussion
### Succession of Microbial Communities and Microbial Interactions  
Flavor compounds play an important role in the quality of Baijiu, and microorganisms are the main contributors to the synthesis of flavor compounds, and show dynamic changes during the process of fermentation [29]. Therefore, exploring the composition and dynamic succession of microorganisms, and the interaction between microorganisms, could offer basic data on how these microorganisms fluctuate and contribute to flavor compound synthesis [36;37]. A total of 192 bacterial genera were detected in all samples at the genus level (Figure 5b). A Venn analysis could reflect the similarity and specificity of microbial genera in different samples [15]. According to the Venn analysis of bacterial microorganisms (Figure 5a), there were 78 bacterial genera in sample 1, 98 bacterial genera in sample 2, 137 bacterial genera in sample 3, and 114 bacterial genera in sample 4, of which 50 bacterial genera were commonly identified in all samples. In addition, it was noteworthy that there were 12, 14, 38, and 14 specific bacterial genera in samples 1, 2, 3, and 4, respectively. There were 20 genera with a relative abundance above 1% in all samples, _Lactobacillus_, _Sporolactobacillus_, _Clostridium sensu stricto 11_, _Clostridium sensu stricto 12_, _Burkholderia_, _Acinetobacter_, _Weissella_, _Bacillus_, _Pediococcus_, _Kosakonia_, _Clostridium sensu stricto 1_, _Achromobacter_, _Lactococcus_, _Escherichia_, _Ochroductrum_, _Enterobacter_, _Klebsiella_, _Leuconstoc_, and _Caproiciproducers_ (Figure 5b). At the initial fermentation stage, the microbial genera that were unfavorable for fermentation (e.g., _Fictibacillus_, _Bacillus_, _Pediococcus_) showed some abundance, but then rapidly decreased during fermentation [12;38;39]. On the contrary, the abundance of _Lactobacillus_ in the experimental group was low at the initial fermentation stage, but showed a high abundance in the fermentation process after 7 days. Compared with all samples, _Lactobacillus_was predominant both in sample 2 on the 28 th day (84.9%) and in sample 4 on the 42 nd day (85.5%), while its abundance reached a maximum (25.7%) on the 14 th day in sample 3 and declined gradually in the middle and late stages of fermentation. Studies indicate that _Lactobacillus_ grows rapidly in a high acidity environment, in accordance with the phenomenon that the acidities of sample 2 and sample 4 increased more rapidly than that of sample 3 [40; 41]. Therefore, _Lactobacillus_ quickly occupied a dominant position and became the main bacterial genus at the end of fermentation in sample 2 and sample 4. This confirms that the acidity of fermented grains plays an important role in the succession of microbial communities. At the same time, the abundance of _Sporolactobacillus_ in sample 1 and sample 3 gradually increased and accounted for the highest proportion of bacteria at the end of fermentation (45.8% and 60.16%, respectively). Studies have shown that _Sporolactobacillus_ is one of the most dominant microorganisms in high-quality pit mud, and plays an important role in the production of flavor compounds in Baijiu [42]. In addition, the bacterial genera _Clostridium_, _Burkholderia_, and _Capriciproducens_, in the designed microbial combination, displayed a high abundance in the fermentation system, which indicated that the added functional microorganisms could colonize the fermentation system and play a role in the fermentation process. For _Clostridium_, _Clostridium sensu stricto_ 12, _Clostridium sensu stricto_ 11, and _Clostridium sensu stricto_ 1 were the dominant microorganisms, among which _Clostridium sensu stricto_ 12 increased gradually in the early fermentation stage, while those of _Clostridium sensu stricto_ 11 and _Clostridium sensu stricto_ 1 increased and stabilized in the middle and late fermentation stages. In addition, the abundance  
Figure 5: Microbial Venn analysis and community composition at the genus level. (**a**,**b**) bacteria, (**c**,**d**) fungi.