## 3 Results
### Analysis of the Microbial Community Composition and Diversity
#### 3.3.2 Analysis of the Microbial Community Composition and Diversity  
To clarify the compositions of the microbial communities in three types of high-temperature _Daqu_, the phylum, genus, and species level were analyzed, and an average relative abundance of over 1.00% was defined as the dominant phyla, genera, or species. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Species**} & \multirow{2}{*}{**Sample**} & \multicolumn{4}{c}{**Richness Indexes**} & \multicolumn{3}{c}{**Diversity Indexes**} \\ \cline{3-8}  & & **[PERSON]** & **ACE** & **Coverage** & **[PERSON]** & **[PERSON]** & **Coverage** \\ \hline \multirow{3}{*}{Bacteria} & \(\mathrm{BQ}\) & 291.55 \(\pm\) 35.07 \({}^{\mathrm{a}}\) & 306.37 \(\pm\) 21.89 \({}^{\mathrm{a}}\) & 0.999 & 2.08 \(\pm\) 0.34 \({}^{\mathrm{a}}\) & 0.36 \(\pm\) 0.04 \({}^{\mathrm{a}}\) & 0.999 \\  & WQ & 122.70 \(\pm\) 10.37 \({}^{\mathrm{b}}\) & 141.17 \(\pm\) 15.94 \({}^{\mathrm{b}}\) & 0.999 & 1.38 \(\pm\) 0.02 \({}^{\mathrm{a}}\) & 0.43 \(\pm\) 0.03 \({}^{\mathrm{a}}\) & 0.999 \\  & YQ & 352.39 \(\pm\) 12.55 \({}^{\mathrm{a}}\) & 361.60 \(\pm\) 19.44 \({}^{\mathrm{a}}\) & 0.999 & 2.67 \(\pm\) 0.14 \({}^{\mathrm{a}}\) & 0.19 \(\pm\) 0.02 \({}^{\mathrm{b}}\) & 0.999 \\ \hline \multirow{3}{*}{Fungi} & \(\mathrm{BQ}\) & 59.83 \(\pm\) 2.95 \({}^{\mathrm{a}}\) & 60.80 \(\pm\) 3.00 \({}^{\mathrm{a}}\) & 0.999 & 1.52 \(\pm\) 0.01 \({}^{\mathrm{a}}\) & 0.32 \(\pm\) 0.01 \({}^{\mathrm{a}}\) & 0.999 \\  & WQ & 48.38 \(\pm\) 0.82 \({}^{\mathrm{b}}\) & 57.81 \(\pm\) 0.68 \({}^{\mathrm{a}}\) & 0.999 & 1.29 \(\pm\) 0.15 \({}^{\mathrm{a}}\) & 0.36 \(\pm\) 0.01 \({}^{\mathrm{a}}\) & 0.999 \\ \cline{1-1}  & YQ & 60.83 \(\pm\) 1.06 \({}^{\mathrm{a}}\) & 69.12 \(\pm\) 3.42 \({}^{\mathrm{a}}\) & 0.999 & 1.04 \(\pm\) 0.07 \({}^{\mathrm{a}}\) & 0.43 \(\pm\) 0.05 \({}^{\mathrm{a}}\) & 0.999 \\ \hline \hline \end{tabular}  
* The different letters indicate significant differences in the physicochemical indexes between the samples (\(p<0.05\)).  
\end{table} 
Table 2: Species \(\alpha\)-diversity indexes among three _Daqu_ samples. Figure 2: Different kinds of volatile compounds in three _Daqu_ types. (**a**) Proportion of different volatile compounds. (**b**) Contents of various volatile compounds. The different letters represent the significant differences in the contents of volatile compounds between the samples (\(p<0.05\)). The dissimilar microbial community profiles are shown in Figure 3. At the bacterial phylum level, Firmicutes, Actinobacteria, and Proteobacteria were prevalent bacterial phyla. (Figure 3a). Overall, Firmicutes was the most abundant in the WQ sample (94.42%), BQ sample (82.21%) and YQ sample (86.33%), and Actinobacteria was significantly higher in the BQ sample (15.29%) than in the YQ sample (12.10%), and the WQ sample (1.07%) was the lowest. Proteobacteria were in the BQ (2.06%), WQ (4.46%), and YQ (1.31%) samples. At the bacterial genus level (Figure 3b), although the bacteria in the three samples were different, _Bacillus_, _Kroppenstedtia_, _Virgibacillus_, _Oceanobacillus_, and _Scopulibacillus_ were prominent bacteria in the three _Daqu_ samples. The dominant bacteria in the BQ sample included _Bacillus_ (47.11%), _Oceanobacillus_ (11.20%), _Virgibacillus_ (9.17%), _Kroppenstedtia_ (3.08%), _Thermoactinomyces_ (1.84%), _norank_f_Pseudonocardiaceae_ (3.00%), _unclassified_C_Bacillus_ (2.55%), _Scopulibacillus_ (1.54%), _Rhodococcus_ (1.10%), and _Saccharomycespora_ (1.01%). Sample WQ's dominant bacteria were _Kroppenstedtia_ (32.65%), _Bacillus_ (29.29%), _Virgibacillus_ (16.36%), _Scopulibacillus_ (7.58%), _unclassified_C_Bacillus_ (5.45%), _Pseudogracilibacillus_ (1.08%) and _Ralstonia_ (4.20%).