## 3 Results
### Plasma Jet Increases \(\alpha\)-Amylase Secretion in A. oryzae
Since no suitable methods were available for measuring the levels of \(\text{NO}_{2}\)\({}^{-}\) and \(\text{NO}_{3}\)\({}^{-}\) in the PDB, they were quantified in water and not PDB in our previous study [18]. In this study, however, the levels of \(\text{NO}_{2}\)\({}^{-}\) and \(\text{NO}_{3}\)\({}^{-}\) in the PDB media were estimated using colorimetric strips. Following plasma treatment on day 0, there was a slight increase (0.074-0.093 mg/L) in the levels of \(\text{H}_{2}\text{O}_{2}\) in the PDB solution over the treatment time. However, the levels dramatically decreased after 3 and 7 days of incubation and showed no significant differences among treatment times (Figure 4a). The overall concentration of \(\text{NO}_{\text{X}}\) was distinctly higher than that of \(\text{H}_{2}\text{O}_{2}\) in the PDB and continually increased with the increasing treatment time, displaying the maximum level after 20 min of treatment (1.993-2.228 mg/L) (Figure 4b). No significant changes in the levels of \(\text{NO}_{\text{X}}\) in the PDB were observed during incubation at each treatment time (Figure 4b). The levels of \(\text{NO}_{2}\)\({}^{-}\) and \(\text{NO}_{3}\)\({}^{-}\) in the PDB solutions were estimated from the intensity of the color that appeared on the test strips. The intensity of the pink color on the strip indicated that the \(\text{NO}_{2}\)\({}^{-}\) level was generally higher than that of \(\text{NO}_{3}\)\({}^{-}\); the levels of \(\text{NO}_{2}\)\({}^{-}\) and \(\text{NO}_{3}\)\({}^{-}\) increased over the treatment time during incubation, with a more obvious elevation in the \(\text{NO}_{2}\)\({}^{-}\) level (Figure 4c). The \(\text{NO}_{2}\)\({}^{-}\) concentration was estimated to be less than 5 mg/L, while the \(\text{NO}_{3}\)\({}^{-}\) concentration was much lower than that. There was a slight decrease in both the \(\text{NO}_{2}\)\({}^{-}\) and \(\text{NO}_{3}\)\({}^{-}\) levels after incubation for 3 and 7 days, as compared with that on day 0 (Figure 4c). To understand the overall oxido-reduction state of the PDB media, the ORP was measured in the PDB media during fungal culture post plasma treatment. An increase in the ORP value indicates that the PDB solution has an elevated oxidizing capability. The ORP level of the PDB media with or without fungal spores displayed a positive value of approximately 249.2 mV before plasma treatment (Figure 5). A slight increase of up to 265.7 mV was observed right after treatment with the NTAPP jet for 20 min (day 0) (Figure 5). During incubation, the ORP continued to increase up to 96 h of incubation (with a maximum ORP of 331.7 mV at 20 min of treatment) and then decreased in both the plasma-treated samples and the control (Figure 5). Generally, the ORP levels were higher in the plasma-treated samples than in the control (0 min) at all incubation times (Figure 5). No significant differences in pH levels (pH = 4.83-4.87) were observed between the plasma-treated samples and the control (0 min) (Figure 6). Figure 4: Evaluation of the reactive oxygen and nitrogen species (RONS) level in the PDB solution post plasma treatment for 5, 10, 15, and 20 min, or without treatment (0 min = control). Following plasma treatment, the PDB was incubated for 0, 3, and 7 days. **(a)** Concentration of \(\text{H}_{2}\text{O}_{2}\). **(b)** Concentration of \(\text{NO}_{\text{X}}\). **(c)** Color change in the \(\text{NO}_{2}\text{${}^{-}$}\) and \(\text{NO}_{3}\text{${}^{-}$}\) strips after soaking in the control and plasma-treated PDB (upper panel), as well as the standard concentrations of \(\text{NO}_{2}\text{${}^{-}$}\) and \(\text{NO}_{3}\text{${}^{-}$}\) according to the color of the strips (bottom panel). In **(a,b)**, each value is indicated as the mean and standard deviation of 6 replicate measurements.