OBJECTIVETo investigate the effect of low-temperature plasma on inactivation of bacterial spores and explore the mechanism.

METHODSDielectric barrier discharge (DBD) was employed to generate the atmospheric low-temperature plasma for treatment of B.subtilis var. niger spores with the gas spacing of 3, 4 and 5 and treatment time intervals of 5, 10, 15, 20, 25, 30 and 35 s. The survived colonies was counted with plate counting method, and the killing log value (KLV) at different treatment times was calculated. The inactivation effect of electric field on B.subtilis var.niger spores was also investigated and the spores treated with low-temperature plasma were observed with transmission electron microscope.

RESULTSWith the gap spacing of 3, 4 and 5 mm, the KLV of low-temperature plasma on B.subtilis var.niger spores within 25, 30 and 35 s of exposure was more than 5. The germicidal effects of the electric field on B. subtilis var.niger spores were rather poor. Transmission electron microscopy demonstrated total destruction of the surface and interior structure of the spores by low-temperature plasma.

CONCLUSIONSLow-temperature plasma is effective for inactivation of the bacterial spores with a time and dose dependence. The penetrating effect of charged particles and oxygenation effect of the reactive oxygen species might play a dominant role in plasma-induced bacterial spore inactivation, while the role of electric field is negligible.