Differential Inactivation of Fungal Spores in Water and on Seeds by Ozone and Arc Discharge Plasma

Abstract

Seed sterilization is essential for preventing seed borne fungal diseases. Sterilization tools based on physical technologies have recently received much attention. However, available information is very limited in terms of efficiency, safety, and mode of action. In this study, we have examined antifungal activity of ozone and arc discharge plasma, potential tools for seed sterilization. In our results, ozone and arc discharge plasma have shown differential antifungal effects, depending on the environment associated with fungal spores (freely submerged in water or infected seeds). Ozone inactivates Fusarium fujikuroi (fungus causing rice bakanae disease) spores submerged in water more efficiently than arc discharge plasma. However, fungal spores associated with or infecting rice seeds are more effectively deactivated by arc discharge plasma. ROS generated in water by ozone may function as a powerful fungicidal factor. On the other hand, shockwave generated from arc discharge plasma may have greatly contributed to antifungal effects on fungus associated with rice seeds. In support of this notion, addition of ultrasonic wave in ozone generating water has greatly increased the efficiency of seed disinfection.

Arc discharge-mediated disassembly of viral particles in water

“…Among these plasma types for water treatment, direct plasma, like a submerged plasma reactor for arc discharge (underwater arc), can be used to treat water directly along with UV radiation, radical species, and shock waves (Lee et al, 2003). Underwater arc treatment is considered to have a higher capability of biological inactivation (Chang, 2001;Kang et al, 2015). However, the utility of underwater arc treatment in the inactivation of enteric viruses such as norovirus remains poorly understood.…”

Design and effectiveness of pulsed electric fields towards seed disinfection

“…New disinfection treatments, such as biological interventions or competitive exclusions and high‐pressure processing, appear to achieve the safe minimum standard of 20 000 ppm calcium hypochlorite use. Since the application of chemical disinfectants in concentrations above 20 000 ppm calcium hypochlorite can pose environmental and public safety risks, alternative intervention approaches should be considered …”

“…Physical methods such as ionizing radiation, radioisotopes, thermal effects, electron flow, laser, and space‐flight breeding are considered to be more environmentally friendly but involve a highly complex and expensive processing. Also, such treatments of higher doses may be highly radioactive, ineffective, or destructive …”

“…Also, such treatments of higher doses may be highly radioactive, ineffective, or destructive. 5,6 Pulsed electric fields (PEFs) involve application of short bursts of high electric field pulses, and the applied electric field is transmitted to a material to be processed by ions conducting the electric fields.…”

Water treatment by the AC gliding arc air plasma

“…There are some holes in their cell shells and some parts of their internal organisms penetrated out. It is known that plasma, especially G Arc discharge, can produce shockwave in water which plays an important role in the detachment of fungal spores [18,19]. Results of measuring pH in water pH of water before and after treatment was measured gradually during the plasma treatment process.…”