## 3 Results and Discussion
### Selected Sugars in Banana Peel Hydrolysates Before and After Yeast Cultivation  
One of the most crucial research objectives was to determine the impact of ultrasound and microwave treatment on the efficiency of banana peel hydrolysis into simple sugars assimilated by yeast. Table 3 (below) summarises the results of the content of selected sugars in the hydrolysate samples before cultivation and in the culture effluents. Analysis of the hydrolysate samples before cultivation showed that the highest glucose content (9.27 \(\pm\) 0.327 g/L) was found in the samples after enzymatic hydrolysis preceded by pressure-thermal treatment (PTE sample). A statistically similar (\(p\) > 0.05) glucose level (8.55 \(\pm\) 0.81 g/L) was determined in the sample after enzymatic hydrolysis preceded by ultrasonic treatment (UE). Slightly less glucose (8.08 \(\pm\) 0.439 g/L) was found in the ME sample after combined microwave and enzymatic treatment. The least amount of glucose was found in the reference hydrolysate obtained after acid-thermal hydrolysis alone. Comparing the dependence of xylose, arabinose and cellobiose concentrations on the hydrolysis method, it can be concluded that the trend observed for glucose was maintained. The lowest amounts of cellobiose, xylose and arabinose were found in the PT sample, 0.02 \(\pm\) 0.001 g/L, 5.56 \(\pm\) 0.298 g/L and 0.73 \(\pm\) 0.071 g/L, respectively. The highest amounts of these sugars were found in the PTE hydrolysate, with 0.29 \(\pm\) 0.026 g/L of cellobiose, 9.24 \(\pm\) 0.703 g/L of xylose and 1.93 \(\pm\) 0.154 g/L of arabinose. After taking into account other substrate loads, our results are similar to those obtained by [PERSON] et al. [48] after hydrolysis of banana peels with a mixture of Celluclast 1.5 L, Novozyme-188 and Pectinase P-2611 preparations. After converting the results to the same ratio of peel dry matter to total sample weight, they determined in the hydrolysate about 0.8 g/L xylose, 1.5 g/L arabinose and 6.1 to 13.2 g/L glucose. [PERSON] et al. [59] hydrolys banana peels using the cellulolytic preparation Onozuka R-10 to obtain significantly lower glucose and xylose concentrations (<1 g/L), although it should be emphasised that the hydrolysis time was very short at just 3 h, not allowing for the hydrolysis of the entire pool of polysaccharides present in the raw material. [PERSON] et al. [60] obtained more than 25 g/L of reducing sugar after 30 h of hydrolysis with a cellulolytic preparation, Cellic CTec2, when hydrolysing banana peels with a similar substrate load (1 g DM/20 mL) as ours. [PERSON] et al. [61] obtained 32.5 g/L of glucose after hydrolysis (with Celluclast 1.5 L) of BP at 20% substrate load. It is worth emphasising the significant amount of sugars released after ultrasound- and microwave-assisted hydrolysis, for which the total pool of sugars in these trials was very similar to those present after traditional acid-thermal treatment with subsequent enzymatic hydrolysis. The time and power of microwave treatment are obvious parameters affecting the intensity of the process. Due to the preliminary nature of our research, after reviewing the literature [39; 41; 43; 44], we decided to use a time of 3 min and an intensity of 600 W. In addition to the specific effect of microwaves on the structure of the raw material, this also allowed the sample to be heated to a temperature of 85-95 \({}^{\circ}\)C, which, in our assumption, improved the extraction of the raw material components. The parameters we set translated