Afterglow dielectric-barrier discharge air plasma (ADDAP) for the inactivation of Escherichia coli O157:H7

Abstract

The afterglow of an atmospheric pressure plasma can conveniently be used for large scale decontamination operations. In the present study, an afterglow dielectric-barrier discharge air plasma (ADDAP) was used to inactivate Escherichia coli O157:H7, which was used as a model microorganism for studying the inactivation effect of the plasma. ADDAP was generated at different input currents in the range of 0.4-0.8 A. At all tested plasma exposure times, temperatures inside sample treatment chamber remained less than 30 degrees C. Regarding chemical composition of ADDAP in the treatment chamber, NOx species (NO and NO2) were predominantly observed. The levels of the NOx species increased as the current intensity increases and the maximum NO and NO2 concentrations noted were 6 and 4 ppm, respectively, but that of CO was less than 1 ppm level at 0.8 A. Upon treatment using ADDAP generated at 0.4-0.8 A for 180 min, glass-bound E. coli O157:H7 counts were reduced in the range of 1.24-2.71 log CFU/mL. The inactivation patterns exhibited better fit to the Weibull tail model. The comparison of delta values indicated that superior inactivation effects were observed as current intensity increases.