title: Investigation of UV-TiO2 photocatalysis and its mechanism in Bacillus subtilis spore inactivation.
abstract: The inactivation levels of Bacillus subtilis spores for various disinfection processes (ultraviolet (UV), TiO2 and UV-TiO2) were compared. The results showed that the inactivation effect of B. subtilis spores by UV treatment alone was far below that for bacteria without endospores. TiO2 alone in the dark, as a control experiment, exhibited almost no inactivation effect. Compared with UV treatment alone, the inactivation effect increased significantly with the addition of TiO2. Increases of the UV irradiance and TiO2 concentration both contributed to the increase of the inactivation effect. Lipid peroxidation was found to be the underlying mechanism of inactivation. Malondialdehyde (MDA), the degradation product of lipid peroxidation, was used as an index to determine the extent of the reaction. The MDA concentration surged surprisingly to 3.24nmol/mg dry cell with the combination disinfection for 600sec (0.10mW/cm(2) irradiance and 10mg/L TiO2). In contrast, for UV alone or TiO2 in the dark, the MDA concentration was 0.38 and 0.25nmol/mg dry cell, respectively, under the same conditions. This indicated that both UV and TiO2 were essential for lipid peroxidation. Changes in cell ultrastructure were observed by transmission electron microscopy. The cell membrane was heavily damaged and cellular contents were completely lysed with the UV-TiO2 process, suggesting that lipid peroxidation was the root of the enhancement in inactivation efficiency.
authors.affiliation: Key Laboratory of Yangtze River Water Environment, Ministry of Education, Tongji University, Shanghai 200092, China. Electronic address: hfzyq1991@126.com.
authors.forename: Yiqing
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science & Engineering, Tongji University, Shanghai 200092, China.
authors.forename: Lingling
authors.initials: L
authors.lastname: Zhou
authors.affiliation: Key Laboratory of Yangtze River Water Environment, Ministry of Education, Tongji University, Shanghai 200092, China. Electronic address: YZHANG112@e.ntu.edu.sg.
authors.forename: Yongji
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D001412:Bacillus subtilis / Q000187:drug effects / Q000528:radiation effects*; D004203:Disinfection / Q000379:methods*; D015227:Lipid Peroxidation / Q000187:drug effects / Q000528:radiation effects; D010782:Photolysis; D013171:Spores, Bacterial / Q000187:drug effects / Q000528:radiation effects*; D014025:Titanium; D014466:Ultraviolet Rays
chemical_list: C009495:titanium dioxide; D014025:Titanium
keywords: Bacillus subtilis spores; Disinfection; Lipid peroxidation; TiO(2); UV