## 2 Materials and Methods
### Yeast Cultures and Biomass Treatments  
The inoculum cultures in flasks were provided in yeast extract, peptone, and glucose medium (YPG). Other shaken cultures were performed in a rich YPO medium. YPG medium consisted of yeast extract (10 g/dm\({}^{3}\)), peptone (20 g/dm\({}^{3}\)), and glucose (20 g/dm\({}^{3}\)) as carbon sources. Instead of glucose as a carbon source, the YPO medium was characterized by including waste rapeseed oil in the composition. The shaken culture media's pH was 5.0, adjusted with concentrated hydrochloric acid.  
The nitrogen source-limited medium was used for shaken cultures and yeast culture in the BIOFLO 3000 laboratory bioreactor from New Brunswick Scientific (Edison, NK, USA) with a working volume of 4 dm\({}^{3}\). Depending on the variant, distilled or untreated tap water was used to prepare the medium. All media, independent of the type of water used, were sterilized in an autoclave at 121 \({}^{\circ}\)C for 15 min using standard sterilization conditions. The culture medium contained rapeseed oil from meat processing plants at a concentration of 50 g/dm\({}^{3}\), along with yeast extract (BTL sp. z o. o., Warsaw, Poland) at 2 g/dm\({}^{3}\) and peptone (BTL sp. z o. o., Warsaw, Poland) at 1 g/dm\({}^{3}\), ammonium sulfate ((NH\({}_{4}\))\({}_{2}\)SO\({}_{4}\)) at 2.5 g/dm\({}^{3}\), potassium dihydrogen phosphate (KH\({}_{2}\)PO\({}_{4}\)) at 7.0 g/dm\({}^{3}\), sodium hydrogen phosphate (Na\({}_{2}\)HPO\({}_{4}\)) at 2.5 g/dm\({}^{3}\), magnesium sulfate (MgSO\({}_{4}\)) at 1.5 g/dm\({}^{3}\), calcium chloride (CaCl\({}_{2}\)) at 0.15 g/dm\({}^{3}\), ferrous sulfate heptahydrate (FeSO\({}_{4}\cdot\)7H\({}_{2}\)O) at 0.16 g/dm\({}^{3}\), zinc sulfate (ZnSO\({}_{4}\)) at 0.02 g/dm\({}^{3}\), and manganese chloride tetrahydrate (MnCl\({}_{2}\)-4H\({}_{2}\)O) at 0.08 g/dm\({}^{3}\). The mineral salts listed were sourced from the following companies: Avantor (Gliwice, Poland) and Chempur (Piekary Slaskie, Poland). The final solution was adjusted to a total volume of 4 dm\({}^{3}\). During the 65 h bioreactor culture, a waste carbon source of 100 g was added at 16, 50, and 62 h for the distilled water-based culture and at 16 h for the tap water-based culture to maintain further yeast cell growth.  
The culture was carried out under conditions of 28 \({}^{\circ}\)C and 200-600 rpm with an adjustable relative oxygenation level of the medium, the concentration of which was maintained at 30% of its initial concentration as measured by an oxygen electrode. During the culture, samples were taken for analysis. In cultures lasting 65 h, biomass was taken at the 43 rd hour of culture and at the end of the culture. In the one-day bioreactor, the biomass was taken at the end of the culture in the 20 th hour. The biomass was collected by centrifugation in an MPW Centrifuge-352 (MPW Med. Instruments, Warsaw, Poland) at 8000 rpm for 10 min. After centrifugation, three layers were formed in the thimble: the first layer at the very top was the residual lipid carbon source, the second was the post-culture fluid, and at the very bottom, as a precipitate, was the yeast cell biomass. The supernatant and the residual lipid carbon source were poured into a separate thimble. The wet biomass was weighed and dried at 105 \({}^{\circ}\)C in a laboratory dryer, then weighed again after drying. The yeast biomass's dry matter (DM) content was calculated from the difference between the wet and dry weights.  
Part of the biomass was lyophilized. Before lyophilization, the yeast biomass was subjected to a quick freezing process at \(-40\)\({}^{\circ}\)C. Freeze-drying was carried out for 24 h in a Christ Gamma 1-16 apparatus (Osterode am Harz, Germany) on a 10 \({}^{\circ}\)C shelf under a pressure of 63 Pa, corresponding to an ice temperature of \(-25\)\({}^{\circ}\)C at thermodynamic equilibrium. The safety pressure was 103 Pa. The material was stored in sealed aluminium foil bags [9].