Mechanisms of direct dielectric barrier discharge plasma inactivation of e. coli

Summary form only given: Bacteria inactivation efficiency of direct atmospheric pressure dielectric barrier discharge treatment has been shown to be extremely strong, however mechanisms of DBD plasma sterilization is still unclear. We have performed a series of experiments which allow to understand bacteria inactivation effects of various active species generated in plasma, including charged particles, neutral short and long living species, and UV photons. Also, we have studied dependence of sterilization efficiency on gas composition and amount of free water which cover bacteria during DBD plasma treatment. The results of these model experiments allowed us to determine conditions in which best sterilization effect on surface of agar may be achieved: fast and effective bacteria inactivation by direct DBD plasma is shown to be related to presence of both positive and negative ions in combination with molecular oxygen and free water molecules and strongly depends on thickness of water layer on top of treated surface. Based on these experimental results we propose possible physical-chemical mechanism of DBD plasma bacteria inactivation.