Photocatalytic bactericidal effect of TiO2 on Enterobacter cloacae: Comparative study with other Gram (−) bacteria

The bactericidal action of heterogeneous photocatalysis (UV-A/TiO2) has been tested on Enterobacter cloacae, a microorganism very resistant to UV-A irradiation. Results have been compared with other representative strains of Gram (−) bacilli of different photosensitivity like E. coli, Pseudomonas aeruginosa and Salmonella typhimurium. The TiO2 photocatalytic technology can inactivate bacteria resistant to oxidative membrane damage caused by direct UV irradiation, like E. cloacae, a common soil and aquatic microorganism, which normally is not affected by low UV-A irradiation intensity. In all cases, sublethal UV-A doses provoked an important lethality in the presence of TiO2. Inactivation rates of the microorganisms are compared and some clues on the mechanism of bacteria destruction are discussed.