## 3 Results
Castor oil was the only source of carbon in the media, necessary for the growth of microorganisms and maintenance of vital functions, and was a substrate of \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Parameter**} & \multirow{2}{*}{**Unit**} & \multicolumn{5}{c}{**Bioreactor Batch Cultures**} \\ \cline{3-6}  & & **1 \({}^{*}\)** & **2** & **3** & **4** \\ \hline Initial concentration of carbon source (S) & g/L & 75 & 50 & 50 & 75 \\ Time (t) & h & (64) & 45 & 45 & 46 \\ Biomass yield (X) & g\({}_{\text{d.w.}}\)/L & 24.43 \(\pm\) 1.73 & 12.93 \(\pm\) 1.31 & 7.17 \(\pm\) 1.45 & 9.60 \(\pm\) 0.95 \\ Maximum concentration of GDL (L\({}_{\text{max}}\)) & g/L & 1.56 \(\pm\) 0.04 & 2.15 \(\pm\) 0.04 & 0.19 \(\pm\) 0.01 & 0.55 \(\pm\) 0.01 \\ Conversion yield of biomass per carbon & \multirow{2}{*}{g\({}_{\text{d.w.}}\)/g} & \multirow{2}{*}{0.326} & \multirow{2}{*}{0.259} & \multirow{2}{*}{0.143} & \multirow{2}{*}{0.128} \\ substrate (Y\({}_{\text{X/S}}\)) & & & & & \\ Conversion yield of GDL per biomass & \multirow{2}{*}{g/g\({}_{\text{d.w.}}\)} & \multirow{2}{*}{0.064} & \multirow{2}{*}{0.166} & \multirow{2}{*}{0.026} & \multirow{2}{*}{0.057} \\  & formed (Y\({}_{\text{L/X}}\)) & & & & \\ Conversion yield of GDL per carbon & \multirow{2}{*}{g/g} & \multirow{2}{*}{0.021} & \multirow{2}{*}{0.043} & \multirow{2}{*}{0.004} & \multirow{2}{*}{0.007} \\ substrate (Y\({}_{\text{L/S}}\)) & & & & & \\ Volumetric rate of GDL production (q\({}_{\text{Lv}}\)) & g/L/h & (0.024) & & & \\ Specific rate of GDL production (q\({}_{\text{L}}\)) & g/g\({}_{\text{d.w.}}\)/h & (0.0017) & 0.0039 & 0.0006 & 0.0012 \\  & & (0.0010) & & & \\ \hline \hline \end{tabular}  
* \({}^{*}\) in the case of bioreactor 1, in which the maximum \(\gamma\)-decalactone biosynthesis did not coincide with the end of the culture, for a better comparison of parameters, the yeast cultures and the kinetic values of lactone biosynthesis were related to the time when the maximum concentration of lactone was reached (values without brackets) or the total cultivation time (values with brackets).  
\end{table} 
Table 3: Kinetic parameters of \(\gamma\)-decalactone biosynthesis in batch bioreactor cultures of \(\gamma\). _lipolytica_, according to the L4 orthogonal array. the \(\beta\)-oxidation pathway leading to the synthesis of GDL. From the point of view of cell viability (Figure 3c), the optimal conditions were natural acidity at pH 7, no regulation, constant intensity of mixing, and a substrate concentration of 75 g/L. Figure 3: The influence of individual factors on the Eta value calculated as the larger, the better when the goal was to maximize (**a**) the concentration of \(\gamma\)-decalactone, (**b**) the biomass yield, and (**c**) the number of living cells of _Y. lipolytica_ in batch culture. The values of the controlled factors used in the batch cultures of _Y. lipolytica_ are described in Table 2.  
To verify the accuracy of the indicated parameters, a fifth biotransformation reaction was performed. In the bioreactor culture, the parameters presented in Table 4 were used as optimal in obtaining the highest concentration of lactone. The course of this culture along with the obtained GDL concentration is shown in Figure 4. The data analysis confirmed that the statistically selected culture parameters allowed for more efficient biotransformation. The concentration of GDL in this reaction was approx. 36% higher than that of the best bioreactor culture from the first stage (Figure 1b). In this experiment, after 24 h of reaction, over 2 g of lactone/L was obtained, and in 41 h, the concentration of lactone was close to 3 g/L (2.93 \(\pm\) 0.33 g/L). The kinetic parameters for this biotransformation reaction (Table 5) confirm the validity of the assumptions of the Taguchi method. The conversion yield of GDL per biomass formed (Y\({}_{\text{L/X}}\)) was higher than the most efficient reaction from the previous stage (Table 3) by approx. 8%.