Characterization of antimicrobial effects triggered by non thermal atmospheric pressure plasmas on microbial biofilms relevant in food processing preservation and packaging The here presented dissertation investigated the molecular mechanisms by which the food industry model bacteria Pseudomonas fluorescens and Listeria monocytogenes grown either as planktonic cultures were inhibited by plasma treated water (PTW) produced by a microwave induced plasma source (MidiPLexc). As a starting point optimal operating parameters were determined with 5 standard liters per minutes(slm)compressed air during the treatment of 10 ml deionized water within a treatment time of up to 15 min (pre treatment time). Treatment times of 1 3 and 5 min were selected (post treatment time). In addition to physical parameters i.e. temperature measurements at different spots at the plasma source during the production of the PTW the chemical composition of PTW was determined by pH measurements chronoamperometry (determination of the H2O2 concentration) ion chromatography (determination of the NO2 NO3 and ONOO concentrations) and mass spectrometry (qualitative determination of the molecules). In addition concentration changes of reactive species over a period of 3 h indicated a decrease of the NO2 concentration as well as an increase of the NO3 and ONOO concentration in the PTW. Microbiological assays i.e. quantification of colony forming units (CFU) fluorescence and XTT assays revealed a significant reduction of the proliferation ability of the cells membrane damages and metabolic activity have been demonstrated for planktonic cultures as well as mono and ... Plasma Biofilm Konfokale Mikroskopie Rasterkraftmikroskopie Fluoreszenzmikroskopie Pseudomonas fluorescens Listeria monocytogenes antimicrobial biofilms food industry non thermal plasma