Influence of catalase and superoxide dismutase on ozone inactivation of Listeria monocytogenes

The effects of ozone at 0,25, 0.40, and 1.00 ppm on Listeria monocytogenes were evaluated in distilled water and phosphate-buffered saline. Difference s in sensitivity to ozone were found to exist among the six strains examine d. Greater cell death was found following exposure at lower temperatures. E arly stationary-phase cells were less sensitive to ozone than mid-exponenti al- and late stationary-phase cells. Ozonation at 1.00 ppm of cabbage inocu lated with L. monocytogenes effectively inactivated all cells after 5 min. The abilities of in vitro catalase and superoxide dismutase to protect the cells from ozone were also examined. Three listerial test strains were inac tivated rapidly upon exposure to ozone. Both catalase and superoxide dismut ase,were found to protect listerial cells from ozone attack, with superoxid e dismutase being more important than catalase in this protection.