Photocatalytic disinfection of sporulating Bacillus subtilis using silver-doped TiO2/SiO2

Abstract

The efficiency of TiO2 supported on porous SiO2 beads (TiO2/SiO2), and Ag-doped TiO2/SiO2 for the photocatalytic disinfection of Bacillus subtilis in aqueous medium was investigated. The photocatalytic activity of Ag-doped TiO2/SiO2 for the disinfection of B. subtilis was larger than that of non-doped TiO2/SiO2 under UV irradiation. B. subtilis, a gram-positive bacterium, has specific features that enable it to form a tough spore to protect itself from extreme environmental conditions. Sporulating B. subtilis is resistant to UV irradiation, desiccation, high temperature, extreme freezing, and chemical disinfectants. While it has no known toxicity, this bacterium is difficult to disinfect. Approximately 5 weeks were required to cultivate the sporulating bacteria, and the presence of spores was subsequently confirmed using the Wirtz method. Typical vegetative B. subtilis was disinfected using both TiO2/SiO2 and Ag-doped TiO2/SiO2 photocatalysts under UV irradiation. However, the sporulating bacteria were only disinfected when using the Ag-TiO2/SiO2 photocatalyst. Although sporulating B. subtilis is a hardy organism, it can be disinfected using an Ag-doped TiO2/SiO2 photocatalyst.