## 3 Results
### Optimization of the Bacterial Culture Conditions Lising RSM  
The antifungal metabolite production was well optimized, and the values of the assessed factors are displayed in Table 5. The resulting equation is as follows:  
\(1/\sqrt{IZ}=0.313021-0.014527\times\text{starch}-0.004163\times\text{peptone}-0.000532\text{temperature}+0.002966\times\text{pH}+0.000019\times\text{ agitation rate}\). Figure 4: Chemical structure of 6-methoxy-1H-Indole-2-carboxylic acid produced by _Bacillus toyonensis_ OXQ071612. Figure 5: Effect of different carbon and nitrogen sources on the antifungal activity of _Bacillus toyonensis_ OXQ071612 against _C. albicans_ ATCC 10231. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Run** & **A: Starch** & **B: Peptone** & **C: Temperature** & **D: pH** & **E: Agitation Rate** & **Observed Inhibition Zone** & **Predicted Inhibition Zone** \\  & & & & & **(mm)** & **(mm)** \\ \hline \(1\) & 5 & 3 & 35 & 7 & 225 & 18.6 & 18.09 \\ \(2\) & 3 & 3 & 30 & 7 & 225 & 13.76 & 14.46 \\ \(3\) & 1 & 3 & 35 & 7 & 225 & 11.76 & 11.43 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Observed and predicted responses of the central composite design runs. The significance of the generated model was assessed using ANOVA (Table 6). The model's F-value was 183.58 (\(p\)-value < 0.0001), demonstrating its significance. The significant model terms were A, B, C, and D, which all have \(p\)-values under 0.05. Additionally, a low coefficient of variation of 1.36 was found, indicating the strong dependability of the experimental values. The coefficient of determination, R\({}^{2}\), which was 0.9829, indicates that the model could account for 98.2% of the response variability. Additionally, a respectable adj R\({}^{2}\) of 0.9775, closely agreeing with the pred R\({}^{2}\) of 0.9712, was attained. Finally, the adequate precision, or signal to noise ratio, was equal to 44.804. This model was therefore appropriate for navigating the design space. The 3D plots in Figure 6a-c illustrate how the IZ is influenced by any two factors. The suggested ideal conditions for maximum production of the 6-methoxy-1H-Indole-2-carboxylic acid were determined to be starch 5 g/L, peptone 5 g/L, an agitation rate of 150 rpm, a pH of 6, and a temperature of 40 \({}^{\circ}\)C.  
The probability of residuals, the Box-Cox transformation and the predicted versus actual values plots are displayed in Figure 7a-c, suggesting the linear pattern, the necessary transformation, and an acceptable correlation between the predicted and the actual data, respectively. In Figure 7d, the residual vs. run plot shows that the points were randomly distributed around zero, which validates the generated model. \begin{table}
\begin{tabular}{l c c c c c c} \hline \hline
**Source** & **Sum of Squares** & **df** & **Mean Square** & **F-Value** & \(p\)**-Value** & \\ \hline Model & 0.0117 & 5 & 0.0023 & 183.58 & \textless{}0.0001 & significant \\ A-Starch source & 0.0106 & 1 & 0.0106 & 827.52 & \textless{}0.0001 & \\ B-peptone source & 0.0009 & 1 & 0.0009 & 67.96 & \textless{}0.0001 & \\ C-Temperature & 0.0001 & 1 & 0.0001 & 6.93 & 0.0181 & \\ D-pH & 0.0001 & 1 & 0.0001 & 8.62 & 0.0097 & \\ E-Agitation rate & 0.0000 & 1 & 0.0000 & 2.05 & 0.1718 & \\ Residual & 0.0002 & 16 & 0.0000 & & & \\ Corrected Total & 0.0119 & 21 & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 6: The results of ANOVA analysis of the CCD model. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Run** & **A: Starch** & **B: Peptone** & **C: Temperature** & **D: pH** & **E: Agitation Rate** & **Observed Inhibition Zone** & **Predicted Inhibition Zone** \\ \hline
4 & 1 & 5 & 40 & 8 & 150 & 12.3 & 12.59 \\
5 & 5 & 5 & 40 & 6 & 150 & 20.3 & 20.01 \\
6 & 5 & 5 & 30 & 6 & 300 & 19 & 18.94 \\
7 & 3 & 3 & 35 & 7 & 150 & 14.76 & 14.99 \\
8 & 5 & 1 & 40 &  
Figure 6: The 3D response surfaces of the five parameters affecting activity of metabolite produced by \(B\). _toyonensis_ OQ071612. When two factors where plotted, the other three factors were kept at optimum levels.