## Results and Discussion
While noting that, the inclusion of glycerol did increase the amount of **2d** product only. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Solvent**} & \multirow{2}{*}{**\% of Solvent [\%]**} & \multicolumn{4}{c}{_anti_} & \multicolumn{2}{c}{_syn_} \\ \cline{3-8}  & & **2a (SS,1/S)** & **2b (S,1/R)** & **ee [\%]** & **2c (S3,1/R)** & **2d (S,R,1/S)** & **ee [\%]** \\  & & & **[\%]** & **[\%]** & **[\%]** & **[\%]** & **[\%]** \\ \hline \multicolumn{8}{c}{_Candidia viswanathi_ AM120} \\ \hline \multirow{3}{*}{Ethanol} & 5 & 51 & 38 & 7 & 69 & 0 & 4 & \textgreater{}99 \\  & 10 & 100 & 0 & 0 & - & 0 & 0 & - \\  & 20 & 100 & 0 & 0 & - & 0 & 0 & - \\ \hline \multirow{3}{*}{Glycerol} & 5 & 0 & 78 & 15 & 67 & 0 & 7 & \textgreater{}99 \\  & 10 & 0.5 & 76 & 16 & 64 & 0 & 7 & \textgreater{}99 \\  & 20 & 1.6 & 65 & 20 & 53 & 0 & 13 & \textgreater{}99 \\ \hline \multirow{3}{*}{Hexane} & 5 & 5 & 76 & 14 & 69 & 0 & 6 & \textgreater{}99 \\  & 10 & 17 & 66 & 10 & 73 & 0 & 7 & \textgreater{}99 \\  & 20 & 17 & 68 & 11 & 73 & 0 & 5 & \textgreater{}99 \\ \hline \multirow{3}{*}{Isopropanol} & 5 & 3 & 81 & 12 & 73 & 0 & 4.0 & \textgreater{}99 \\  & 10 & 1 & 81 & 14 & 71 & 0 & 4 & \textgreater{}99 \\  & 20 & 3 & 78 & 17 & 65 & 0 & 2 & \textgreater{}99 \\ \hline \multicolumn{8}{c}{_Yarrowia lipolytica_ P26a} \\ \hline \multirow{3}{*}{Ethanol} & 5 & 8 & 0 & 92 & \textgreater{}99 & 0 & 0 & - \\  & 10 & 96 & 0 & 4 & \textgreater{}99 & 0 & 0 & - \\  & 20 & 100 & 0 & 0 & - & 0 & 0 & - \\ \hline \multirow{3}{*}{Glycerol} & 5 & 0 & 100 & \textgreater{}99 & 0 & 0 & - \\  & 10 & 0 & 0 & 100 & \textgreater{}99 & 0 & 0 & - \\ \cline{1-1}  & 20 & 1 & 0 & 93 & \textgreater{}99 & 6 & 0 & \textgreater{}99 \\ \hline \multirow{3}{*}{Hexane} & 5 & 0 & 0 & 100 & \textgreater{}99 & 0 & 0 & - \\  & 10 & 0 & 0 & 100 & \textgreater{}99 & 0 & 0 & - \\ \cline{1-1}  & 20 & 0 & 0 & 94 & \textgreater{}99 & 5 & 1 & 53 \\ \hline \multirow{3}{*}{Isopropanol} & 5 & 3 & 0 & 95 & \textgreater{}99.9 & 0 & 2 & \textgreater{}99 \\  & 10 & 2 & 0 & 97 & \textgreater{}99.9 & 0 & 1 & \textgreater{}99 \\ \cline{1-1}  & 20 & 8 & 0 & 91 & \textgreater{}99.9 & 0 & 1 & \textgreater{}99 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: The biotransformation of \(\alpha\)-acetylbutyrateolactone **1** by _Candidia viswanathi_ AM120 and _Yarrowia lipolytica_ P26A in mixtures of medium with different solvents in different proportions after 1 day (in % according to GC). Overall, all four solvents used in the experiment resulted in the reduction of the enantiomeric excess of the _anti_ diastereoisomer. The addition of isopropanol also slightly decreased conversion of substrate by the culture of _Y. lipolytica_ P26A. Moreover, with isopropanol present, formation of the **2d** product was observed, which was absent in biotransformation without the presence of solvent. Use of up to 10% glycerol or hexane was ineffective. However, the 20% addition of these solvents led to the formation of trace amounts of stereoisomers **2c** and **2d**. Finally, our study concluded with the biotransformation of **1** by _C. viswanathi_ AM120 in phosphate buffer pH = 7 supplemented with deep eutectic solvent, which is a mixture of choline chloride and glycerol in a ratio of 1:2. The reaction was continued until the substrate was completely reduced, but no longer than 7 days (Table 6). If we compare the results obtained from both the biotransformation conducted in just buffer versus in buffer supplemented with DES, the advantage of DES can be noted. The 10% and 25% DES addition reduced the time of transformation to 2 days. With regards to selectivity, DES positively influenced enantio- and stereoselectivity in the process, meaning that it caused an increase. The predominant product was still ster-eoisomer **2a**, as the reaction mixture comprised about 80%. Unfortunately, the use of the DES mixture at 50% had adverse effects on the reaction.