Evidence of mass transfer limitation in the inactivation of pantoea agglomerans biofilms with atmospheric cold gas plasma

The susceptibility of the biofilm-forming bacterium Pantoea agglomerans to the lethal effects of cold atmospheric gas plasmas was investigated. When biofilms of P. agglomerans were produced on membranes and treated using a gas plasma, young biofilms (<; 10 h old) showed viability reductions of between 4 and 5 log10 when treated for 300 s. Biofilms aged 20 or 30 h were reduced by approximately 1 log10 and biofilms aged 40 or 100 h were unaffected by the gas plasma. When the extracellular polysaccharide substances (EPS) in which the cells were embedded was removed and the cells redeposited onto membranes and treated with gas plasma, the microbial reduction was about 3 log10 for 40 h old biofilms and 2 log10 for 100 hour old biofilms. Furthermore, the biofilm thickness was about 20 μm for biofilms younger than 20 h, whilst it was 40 μm and 100 μm for biofilms 70 hours and 100 hours old, respectively.