Synergistic actions of bacillus subtilis devitaliztion by atmosphere plasma jet

Summary form only given. Plasma sterilization have been widely studied in recent years. However, the devitalization mechanisms of micro-organisms by plasma have not been clearly explained. In this study, an atmospheric pressure dielectric barrier discharge plasma jet using Ar or Ar + O₂ as the working gas was designed to explore the devitalization mechanisms of Bacillus subtilis. A set of physical or chemical methods were used to characterize the following sterilization factors: heat, ultraviolet radiation, charged species and chemical reactive species generated by the plasma. About four orders of magnitude of B. subtilis cfu reduced after 60 s plasma treatment, which were two orders of magnitude larger than Ar plasma, and they were totally inactivated at 180 s. Experimental results shown that the bacterial inactivation efficacy had a significant improvement when oxygen was introduced into the plasma jet system. The emission spectra result indicated that O₂ in plasma environment could be decomposed reactive oxygen species and produced O₃, and these chemically active species played a significant role in for inactivation the bacteria. Moreover, the intensity (a.u.) of O IV radical increased evidently in Ar + O₂ plasma. From the results of heat, UV, protein leakage, the malondialdehyde (MDA) production and SEM images, these were showed that heat or UV radiation was not significant in the deactivation. Comparing with the result of sterilization, the inactivation process was dominantly controlled by synergistic actions of chemically active species and charged species, rather than heat, or ultraviolet radiation.