Study on Inactivation Mechanism of an Atmospheric DBD Plasma Jet using Escherichia coli Mutants

Abstract

Inactivation mechanism was investigated using biological method in an atmospheric pressure plasma jet with a plane-to-plane DBD structure. This plasma jet, fed by helium/oxygen gas, was operated by a sub-microsecond pulsed voltage with a repetition rate of 1-10kHz range. The electrical property of the discharge was studied by means of a classical DBD model. The optical property was analyzed by spectroscopy. Escherichia coli K-12 strains, MG1655, BW25113 and CSH26 with their mutants, totally 8 kinds of bacteria, were employed to separate various bactericidal plasma agents. Results showed that oxidative stress and charged species are playing the most significant roles in inactivation process, which was also verified by the indirect inactivation experiments with mesh insertion. Rather than the superoxide O₂^-, neutral reactive oxygen species like O₃ and metastable state O₂^* were identified as dominant sources for oxidative stress.