ABSTRACT
BACKGROUND: Titanium dioxide (TiO2) thin film photocatalyst generates strong oxidizing power when illuminated with Ultra Violet (UV) light with wavelengths of less than 385 nm. In this study, we evaluated the bactericidal activity of it against Escherichia coli, Aspergillus fumigatus and Mycobacterium tuberculosis. METHODS: The TiO2 film were prepared from titanium isopropoxide solution and it was coated on either inner(test) or outer(control) side on Petri dish. annealing at 500 degrees C. The test and control suspension of E. coli, A. fumigatus and M. tuberculosis were grown in the chamber coated inner and outer side. respectively with UV light. For the blank, cell suspensions were grown in TiO2 coated Petri dishes without UV light. The bactericidal activities were estimated by survival ratio calculated from the number of viable cells which form the nutrient agar. RESULTS: In the test, the survival ratio for E. coli and M tuberculosis decreased to a negligible level (i.e., essentially complete sterilization) within 1hr and 2 hr, respectively. and that for 11. fumigatus decreased markedly to about 15% within 6 hr. In the control, the survival ratio for E. coli, A. fumigatus and M. tuberculosis decreased to 40% within 150 min. 6 he and 2 hr, respectively. In the blank, the survival ratio for E. coli and M tuberculosis decreased only about 67% within 150 min and 40% within 2hr. In A. fumigatus, TiO2 only caused little Sterilization within 4 hr. CONCLUSIONS: TiO2 photocatalysts under UV light clearly showed bactericidal activity against E. coli, A. fumigarus and M. tuberculosis. This feature render TiO2 photocatalysts to be applicable to eliminate microorganism from indoor air environment combined with ventilation.