Sterilization effect of UV light on Bacillus spores using TiO2 films depends on wavelength

Abstract

UV light and photocatalysts such as titanium dioxide (TiO2) and silver (Ag) are useful for disinfection of water and surfaces. However, the effect of UV wavelength on photocatalytic disinfection of spores is not well understood. Inactivation of Bacillus spores has been examined using different UV wavelengths and TiO2 or TiO2/Ag composite materials. The level of UVA disinfection of Bacillus anthracis and Bacillus brevis vegetative cells increased with the presence of the TiO2 and Ag photocatalysts, but had little effect on their spores. B. brevis spores were slightly more sensitive to UVB and UVC than the spores of B. atrophaeus. Photocatalytic sterilization against spores was strongest in UVC and UVB and weakest in UVA. The rate of inactivation of Bacillus spores was significantly increased by the presence of TiO2, but was not markedly different from that induced by the presence of Ag. Therefore, TiO2/Ag plus UVA can be used for the sterilization of vegetative cells, while TiO2 and UVC are effective against spores.