## 3 Results
### Characteristics of Microbial Oil Extracted from Y. lipolytica Yeast Cells
Radicals, as intermediate products of oxidation, can negatively affect human health. Factors favouring the oxidation of fats include light, oxygen, and high temperature. Key factors affecting the oxidation rate include the composition of fatty acids and the presence of prooxidants and antioxidants. Oils that contain polyunsaturated fatty acids are the most susceptible to oxidation [52]. The PDSC method was used to observe the stability and shelf life of the microbial oil obtained in this study by checking the oxidation induction time, i.e., the initial step of the fat oxidation process and the maximum oxidation time of the microbial oil. A longer oxidation induction time indicated greater oxidative stability of the oil (Figure 5). Microbial oil extracted from cells from a 20 h culture had the lowest oxidative stability values. Oil extracted from yeast cells grown in culture in a distilled water-based medium showed the highest stability and \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{3}{*}{**Fatty Acid**} & \multirow{3}{*}{**Symbol**} & \multicolumn{3}{c}{**65 h Fed-Batch**} & \multirow{3}{*}{**65 h Fed-Batch**} & \multirow{3}{*}{**20 h Fed-Batch**} & \multirow{3}{*}{**Shaken**} \\  & & **Waste Oil** & & **Culture in** & & **Culture in Tap** & **Culture in Tap** \\  & & **(Carbon** & **Distilled** & **Water-Based** & **Water-Based** & **Water-Based** & **Rich YPO** \\  & & & **Medium** & **Medium** & **Medium** & **Medium** \\ \hline Myristic acid & 14:0 & 0.10 & 0.00 & 0.07 (\(\pm\)0.02) & 0.11 (\(\pm\)0.01) & 0.00 \\ Palmitic acid & 16:0 & 11.50 & 5.07 (\(\pm\)0.06) & 4.46 (\(\pm\)0.14) & 3.71 (\(\pm\)0.14) & 5.39 (\(\pm\)0.01) \\ Palmitoleic acid & 16:1 & 0.66 & 0.07 (\(\pm\)0.03) & 0.00 & 0.22 (\(\pm\)0.03) & 0.50 (\(\pm\)0.03) \\ Stearic acid & 18:0 & 4.32 & 2.00 (\(\pm\)0.03) & 2.05 (\(\pm\)0.02) & 2.55(0.14) & 1.25 (\(\pm\)0.05) \\ Oleic acid & 18:1 & 59.79 & 66.44 (\(\pm\)0.06) & 65.36 (\(\pm\)0.86) & 66.55 (\(\pm\)0.49) & 62.73 (\(\pm\)1.32) \\ Linoleic acid & 18:2 & 16.58 & 19.40 (\(\pm\)0.28) & 19.52 (\(\pm\)0.69) & 18.88 (\(\pm\)0.28) & 21.40 (\(\pm\)0.66) \\ Linolenic acid & 18:3 & 5.22 & 5.56 (\(\pm\)0.20) & 6.77 (\(\pm\)0.46) & 6.14 (\(\pm\)0.07) & 8.72 (\(\pm\)1.95) \\ Arachidic acid & 20:0 & 0.89 & 0.29 (\(\pm\)0.01) & 0.50 (\(\pm\)0.03) & 0.41 (\(\pm\)0.07) & 0.00 \\ Isocenic acid & 20:1 & 0.94 & 1.02 (\(\pm\)0.05) & 1.14 (\(\pm\)0.08) & 0.87 (\(\pm\)0.02) & 0.00 \\ Erucic acid & 22:1 & 0.00 & 0.14 (\(\pm\)0.05) & 0.12 (\(\pm\)0.03) & 0.58 (\(\pm\)0.05) & 0.00 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: The fatty acid content of the microbial oils of _Y. lipolytica_ yeast multiplied in cultures in a bioreactor in a nitrogen source-limited medium, a rich YPO medium without nitrogen limitation, and in post-frying waste oil used as a carbon source (standard deviation is given in brackets) (_p_ < 0.05). persistence. Similar conclusions could be made when analysing the maximum oxidation time (Figure 6). Microbial oil extracted from yeast cells characterized as cells derived from the stationary phase had significantly higher oxidation stability. In the study by [PERSON] et al. (2022), where post-frying rapeseed oil was used in culture, the value of the T max parameter was 26.23 min in a 62 h culture ([PERSON] et al., 2019), which is very similar to our results obtained in a 65 h culture with distilled water. In a study by [PERSON] et al. (2019) ([PERSON] et al., 2019), where oil derived from roasted hemp seeds was analysed, the oxidation induction time ranged from 13.6 to 28.9 min. Compared to other oils, hemp oil is  
Figure 5: Oxidation induction time of microbial oils of _Y. lipolytica_ yeast multiplied in bioreactor cultures in nitrogen source-limited medium and in rich YPO medium without nitrogen limitation (_p_ < 0.05). \({}^{\text{a,b,c}}\)—non-homogeneous groups. Figure 6: Maximum oxidation time of microbial oils of _Y. lipolytica_ yeast multiplied in bioreactor cultures in nitrogen source-limited medium and in rich YPO medium without nitrogen limitation (_p_ < 0.05).