## 3 Bio-Utilization of Waste from the Agri-Food Industry during SCP Production
After this period, it is necessary to filtrate the solution through Wattman filter paper and dilute it with distilled water, before bringing the solution to pH 4.5 using 2.5 M sodium hydroxide [67]. [PERSON] and [PERSON] [68] conducted research on the production of SCP using pineapple waste. The raw materials for the production of the medium were peelings, stems and other unwanted parts of fruit. The waste was rinsed with distilled water, cut into smaller parts, pulverized and filtered. Seven media were prepared, differing in the concentration of the resulting filtrate, each containing 100 mL. The media contained 100, 90, 80, 70, 60, 50, and 40% of the extract of pineapple waste, respectively, and the remainder was distilled water. The media were inoculated with 1 mL of _S. cerevisiae_ yeast culture. The aerobic fermentation process lasted 120 h at a temperature of 25 \({}^{\circ}\)C. Colony-forming units (CFU) were measured every 24 h. During the first 96 h, the highest increase in biomass was observed for the medium with a FW content of 50%. After 5 days of cultivation, the highest increase in biomass was observed in the medium with 60% FW content and it amounted to 3.03 \(\times\) 10\({}^{9}\) CFU/100 mL. Smaller growth was observed for the substrate with 50, 40, 70, 80, 9  
and 80% FW content, respectively. In the case of 90 and 100% media, the number of cells dropped to 0 after 48 h. Pineapple waste is rich in sugars, and thus, a high concentration of this ingredient in the medium, and therefore high osmotic pressure, adversely affects the growth of biomass. Waste from pineapple processing has a high potential for the use as a medium for SCP. However, it is important to ensure the appropriate sugar concentration so that the efficiency of the fermentation process is as high as possible. [PERSON] et al. [64] used waste from olive oil production as a medium component for SCP production. The waste was subjected to alkaline hydrolysis to extract sugars. The process was carried out at different temperatures (50, 75, and 100 \({}^{\circ}\)C) and for different amounts of time (45, 60, and 90 min). Hydrolysis using 0.8 M NaOH at a temperature of 100 \({}^{\circ}\)C for 60 min allowed for the extraction of most sugars (12.5%). The waste prepared in this way was used to produce fermentation media for the yeast _Candida lipolytica_. The fermentation was carried out for 8 days at 30 \({}^{\circ}\)C. Starting from day 3, the content of biomass and protein was determined every day. The highest protein concentration was obtained on day 4. The protein content was just over 9 g/L and the protein to biomass ratio was 69.23%. In order to determine the optimal cultivation conditions, the influence of the pH of the medium and the content of peptone as a nitrogen source were also examined. The optimal conditions were set at a pH of 5.5 and a peptone content of 0.4%. Such a selection of parameters allowed us to obtain 11.24 g/L of protein and a protein-to-biomass ratio of 64.04%. The alkaline hydrolysis of waste, the selection of the appropriate pH, and the addition of peptone allow us to conclude that olive oil waste can be a good substrate for the production of breeding medium for SCP production [64]. [PERSON] et al. [69] conducted research using date fruit processing waste as a raw material for the media for the production of SCP. The waste consisted mainly of date fibers and seeds. The media for SCP production consisted of 25% date waste, 2% agar, 0.3% ammonium sulfate, and the rest was water. Flasks with medium were inoculated with five fungal strains that belonged to the species _Trichoderma reesei, F. venentatum, Thermomyces lamuginosus, A. oryzae_, and _Fusarium germinearum_. For 120 h, the flask of T. lamuginosus was incubated at 45 \({}^{\circ}\)C, and the remaining species at 25 \({}^{\circ}\)C. The biomass and substrate were then dried and powdered, and their protein content was tested. The research showed that the highest increase in biomass and the highest protein content (7.63%) was obtained for the _A. oryzae_ strain.