Study of elementary inactivation processes acting during sterilization of eucaryotic systems in dielectric barrier discharge

This diploma thesis is focused on studying of the effect of the dielectric barrier discharge (DBD) on eucaryotic microorganisms. Plasma sterilization is considered to be an alternative method to conventional sterilization processes. Contrary to standard decontamination methods it doesn´t stress exposed material by heat, pressure and chemicals. Plasma acts on eucaryotic and procaryotic systems by means of synergy of three inactivation mechanisms. They are various reactive species, UV radiation and heat. The Aspergillus niger has been chosen as a bio-indicator enabling to evaluate the effect of plasma assisted microbial inactivation. Plasma was generated in dielectric barrier discharge (DBD) at atmospheric pressure. Nitrogen and argon were used as working gases, paper and PET foil were used as carrying media. The influence of various working conditions on the sterilization effect was studied. Namely it was the influence of plasma exposition time, plasma power density, the type of operating gas and type of supporting medium. The effect of UV radiation in combination with temperature, temperature and direct plasma were studied separately. According to our results the efficiency of DBD increases with plasma power density, resp. plasma exposition time. When comparing sterilization efficiency of nitrogen and argon operating at the same conditions, the higher sterilization effect was observed in argon. The influence of the carrying medium on sterilization effectiveness was proved. It was caused by the different structure of surface. It was found out, that in our experimental setup the active species are probably the main inactivation mechanism. The influence of temperature on inactivation of microorganisms was negligible. The combination of UV radiation and temperature reached the decontamination level about 2 orders. The discharge parameters were studied by means of optical emmision spectroscopy. Scanning electron microscopy enabled to evaluate possible damage of exposed materials through DBD