## 4 Discussion  
As compared with our previous study [18], in the present study, we scaled up the number of fungal spores (from 7.5 \(\times\) 10\({}^{7}\) to 3 \(\times\) 10\({}^{8}\)) and the media volume being treated (from 15 mL to 300 mL), in addition to changing the plasma source from a micro-DBD (dielectric barrier discharge) plane-type plasma to a plasma jet. Our results demonstrated that the plasma jet, like the micro-DBD plant-type plasma used in our previous study, can promote the germination of fungal spores and \(\alpha\)-amylase activity in media. In addition, plasma treatment resulted in similar effects on fungal germination and enzyme activity under the scaled-up condition of the samples. Together with our previous results [15], we concluded that plasma treatment (micro-DBD plane-type plasma or plasma jet) was clearly effective for fungal spore germination, although the subsequent hyphal growth was not always enhanced. Spore germination was improved upon plasma treatment for a shorter time (5-10 min), while longer treatments did not cause significant changes. Dose-dependent activation and inactivation have been observed in mammalian cells, with increased cell proliferation being observed at low doses of plasma and cell death being observed at high doses [29]. Compared to spore germination, an increase in \(\alpha\)-amylase activity in the media was observed upon a relatively longer period of plasma treatment (10-15 min). The plasma-induced enhancement effect was more dramatic during early incubation (24-96 h) than later. This may be because of the aging of the culture media and fungal cells. A promising implication from our results is that \(\alpha\)-amylase activity in media can be promoted by plasma treatment without using induction media for enzyme secretion, as our experiments were carried out in PBD media, not induction media. The enhanced \(\alpha\)-amylase activity in media may be a result of the increased secretion of enzyme protein from fungal hyphae, or the enhanced activity of \(\alpha\)-amylase already secreted into the media, or both. Intriguingly, we did not observe a significant difference in the total protein amount in the media between the control and the plasma-treated samples. This indicates that the enhanced \(\alpha\)-amylase activity in the media may not be a result of enzyme secretion from fungal hyphae. However, we did observe a slight increase in the \(\alpha\)-amylase protein levels in the PDB media in our previous study, and it is possible that the protein levels were possibly too small to be detected using a Bradford assay. Thus, other methods for the quantification of \(\alpha\)-amylase protein levels may need to be identified. The elevated secretion of enzymes upon plasma treatment has also been demonstrated by [PERSON] et al. [14], who showed that treatment with plasma caused an increase in the protein amount and activity of the phytase enzyme in culture media. Their study also demonstrated that plasma could enhance the activity of isolated enzymes by unfolding the tertiary structure of the enzyme slightly. Although the protein levels of the \(\alpha\)-amylase secreted into the media were not quantified in our study,