Bacterial inactivation by plasma treated water enhanced by reactive nitrogen species

There is a growing body of literature that recognizes the importance of plasma treated water (PTW) for inactivation of microorganism. However, very little attention has been paid to the role of reactive nitrogen species (RNS) in deactivation of bacteria. The aim of this study is to explore the role of RNS in bacterial killing, and to develop a plasma system with increased sterilization efficiency. To increase the concentration of reactive oxygen and nitrogen species (RONS) in solution, we have used vapor systems (DI water/HNO₃ at different wt%) combined with plasma using N₂ as working gas. The results show that the addition of the vapor system yields higher RONS contents. Furthermore, PTW produced by N₂ + 0.5 wt% HNO₃ vapor comprises a large amount of both RNS and ROS, while PTW created by N₂ + H₂O vapor consists of a large amount of ROS, but much less RNS. Interestingly, we observed more deactivation of E. Coli with PTW created by N₂ + 0.5 wt% HNO₃ vapor plasma as compared to PTW generated by the other plasma systems. This work provides new insight into the role of RNS along with ROS for deactivation of bacteria.