TiO2-based photocatalyst Generated Reactive Oxygen Species cause cell membrane disruption of Staphylococcus aureus and Escherichia coli O157:H7

Abstract

Photocatalysts, including titanium dioxide (TiO2), have attracted much attention in food safety for controlling foodborne pathogens. However, the study of the photocatalytic activity on various food-surrounding media and the factors that affect the efficacy of photocatalytic inactivation is incomplete. In this study, to inactivate foodborne pathogens in food-surrounding environments, TiO2-based photocatalysts with ultraviolet A (UVA, 365 nm) and visible light (VIS, 405 nm) were employed. Three TiO2-based photocatalysts, namely, Degussa P25 TiO2, carbon-modified KRONOClean 7000® (C–TiO2), and Pt-doped Ishihara-Sangyo MPT-623 (Pt–TiO2) inactivated Staphylococcus aureus and Escherichia coli O157:H7 exposed to UVA and VIS light in both water and air samples. Among them, Degussa P25 under UVA showed the highest bactericidal effects in both water and air treatments, which induced 5.19 log reductions in S. aureus when treated for 11.68 J/cm2, and E. coli O157:H7 was reduced by more than 6.21 log for 1.32 J/cm2 in the water sample. For air treatment, the combination of Degussa P25 and UVA achieved 3.45 and 3.28 log reductions for Staphylococcus aureus and E. coli O157:H7, respectively, in a developed laboratory-scale chamber for 1 h and 20.02 J/cm2. Scavenger assays showed that regardless of the photocatalyst and wavelength used, reactive oxygen species (ROS) generation causes cell membrane disruption of foodborne pathogens. However, the types of ROS that are generated vary among the photocatalysts and are related to different bactericidal efficacies. These results indicated that TiO2-based photocatalytic activity can be used to control microbiological hazards in various environments in the food industry.