Dielectric barrier discharge plasma treatment on E. coli: Influence of CH4/N2, O2, N2/O2, N2, and Ar gases

Atmospheric pressure dielectric barrier discharge (DBD) plasma has been employed on Gram-negative bacteria, Escherichia coli BL21. Treatment was carried out using plasma generated with different compositions of gases: CH4/N2 (1:2), O2, N2/O2 (1:1), N2, and Ar, and by varying plasma power and treatment time. E. coli cells were exposed under the DBD plasma in triplicates, and their surviving numbers were observed in terms of colony forming units. It has been observed that the CH4/N2 plasma exhibits relatively higher sterilization property toward E. coli compared to plasma generated by using O2, N2/O2, N2, and Ar gas mixtures. The time to kill up to 90% of the initial population of the E. coli cells was found to be about 2-3 min for CH4/N2 and O2 gas mixture DBD plasma. A prolongation of treatment time and an increase in the dissipated power significantly improved the E. coli killing efficiency of the atmospheric pressure DBD plasma.