## 3 Results and Discussion
This is a satisfactory result because the yeast was the most often isolated fungi, and _Bacillus megaterium_ is resistant to ozonation due to the production of spores. The lower sensitivity of molds is due to the high resistance of these microorganisms to antimicrobial agents (spore production, chemical composition, and thickness of the cell wall). Surprisingly, there was no elimination of Gram-negative _Pseudomonas fluorescens_ in the parsley samples. Gram-negative rods of oxidase-positive bacteria were isolated at a frequency of 18-33% (Figure 2). The presence of organic contaminations had a significant impact on the number of microorganisms during ozonation (Figure 3, Table S2). A concentration of 1% organic compounds (in the form of a nutrient medium) decreased the reduction in the number of microorganisms. This was especially important for yeasts and molds, where reduction decreased to levels of R = 19-66%. (Figure 3). Statistically significant differences were  
Figure 3: Reductions in numbers of microorganisms after 15 min of ozonation with different concentrations of ozone (0.5 mg and 1.5 O\({}_{3}\) mg/L) and organic compounds (0.1%, 1%, 10%, 50%). found in the reduction in _C. cladosporoides_ mold depending on the number of organic contaminants. A concentration of 50% organic contaminants resulted in no reduction (Table S2). In addition, statistical differences in reduction were observed for this mold at an ozone dose of 1.5 mg/L with contamination levels in the medium of 0.1% and 1%. These observations also concerned _B. alba_ and _R. babjevae_ yeasts. There was no reduction after ozonation with 10% organic contamination. Statistically significant differences in reduction were observed for yeasts with 1% contamination (Table S2). Higher concentrations of organic compounds corresponded to the lower effectiveness of ozonation. However, the addition of organic compounds did not have a significant effect on the high efficiency of ozonation against the tested bacteria (R = 98-100%) (Figure 3). Statistical analysis showed no differences in the reduction in _S. warneri_ bacteria at a dose of contamination above 1% (Table S2). A good effect reducing the number of _Pseudomonas fluorescens_ was achieved after 15 min at both doses, 0.5 and 1.5 O\({}_{3}\) mg/L. In the case of this strain, there was no statistically significant effect of the level of contamination on the efficiency of the ozonation process, which was slightly higher at a higher dose of ozone. Similarly, there were no differences relevant to the _B. megaterium_ strain. The reduction was high at both doses, regardless of the level of contamination (Figure 3, Table S2). Previous model studies have proven that high microbial inhibition rates can be obtained by aqueous and gaseous ozonation, including pathogens _Shigella sounei_, _Escherichia coli_ O157:H7, _Salmonella_ Typhimurium, _Yersinia enterocolita_, and natural microflora [23; 56; 57; 58; 59; 60]. However, there have been few studies on parsley leaves. Our studies on parsley isolates confirmed the effectiveness of ozonation in removing microorganisms from water. On the other hand, ozone may have some harmful effects on different plant products, such as losses in color, antioxidant constituents, etc., due to its strong oxidizing activity [61; 62; 63]. Therefore, in the next stage of this study, we investigated the dose and ozonation time determined under model conditions (1.5 mg/L, 3, 5, 10, 15 min), simulating the process in an industrial plant. During ozonation, the reduction in bacteria and fungi on parsley was measured in relation to the control (before the process). Different weights of parsley were used (25, 50, 75, 100 g). The control sample was parsley rinsed in tap water. The results are presented in Figure 4 and Table S3. Figure 4: Reduction in number of microorganisms (fungi and bacteria) in parsley samples rinsed with ozonated water (ozone concentration 1.5 mg/L) in a closed circuit (3, 5, 10, 15 min). Satisfactory results were obtained after 3 min of ozonation.