Effect of N2/O2 composition on inactivation efficiency of Escherichia coli by discharge plasma at the gas-solution interface

Abstract

PurposeBacterial inactivation by discharge plasma is affected by many factors including gas type. No uniform conclusion for the effect of working gas type on the inactivation efficiency has been reached until now. In this work, the gas type and composition on the bactericidal efficiency of discharge plasma were systemically investigated. MethodsThe inactivation behaviors of Escherichia coli (E. coli) by corona discharge plasma at the gas-solution interface produced using needle high-voltage electrode above the liquid with shielding O2, N2, and air were systemically compared. The reactive species produced in solution were detected and their correlation with the bactericidal efficiency was found. ResultsAir plasma has strong sterilization capability, followed by N2 plasma, while O2 plasma has the lowest sterilization capability. The bactericidal abilities of different gas plasma is in positive correlation with the produced nitrite concentration in solution. ConclusionThe reason for the gas type and composition to influence the sterilization capability was due to that they influenced the nitrite production in solution which further reacted with plasma-produced hydrogen peroxide in acidified medium to form a strong oxidant peroxynitrite. The produced peroxynitrite could damage both the membrane and DNA, especially the former, and consequently inactivate the bacteria lethally.