München 2019 – wissenschaftliches Programm

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P: Fachverband Plasmaphysik

P 11: Atmospheric Pressure Plasmas III

P 11.5: Vortrag

Dienstag, 19. März 2019, 15:15–15:30, HS 21

Inactivation Depth of E.coli Biofilm in Liquids by a Surface Micro-discharge — •chen-yon tobias tschang and markus thoma — I. Physikalisches Institut, Justus-Liebig Universität Gießen

In this study, we investigated the inactivation of Escherichia coli (E. coli) biofilm under different depths below liquid surface by two modes of a surface micro-discharge (SMD). Recently, plasma liquid sterilization had been shown to be strongly effective, yet the mechanisms are complex and not well understood. Therefore, we developed a simple method to evaluate the inactivation depth of bacteria biofilm. As E. coli are motile bacteria, the tendency of forming biofilm on the gas-liquid interface were used to produce samples with different distance under liquid surface. The plasma source, in our study, is a SMD driven by 5 kHz sinusoidal power input with peak to peak voltage of 8 kV for ozone mode and 12 kV for nitric oxide mode. Inactivation of microbes were tested by BacTiter-Glo assay. Gas phase ozone were evaluated by UV absorption of 254 nm. Radicals in liquid were examined by indigo method for ozone and nitrite/nitrate colorimetric assay. To evaluated the inactivation effect of UV, a MgF₂ plate was applied. Results indicates different inactivation mechanism by two plasma modes. For ozone mode, the inactivation was observed stronger on liquid surface which is believed to be related to the dissolved ozone, while a relatively homogeneous inactivation was observed for nitric oxide mode.