Photocatalytic inhibition of microbial adhesion by anodized titanium.

Biofouling is one of the concerns in the use of titanium for seawater cooled condensers of power plants. Earlier studies have shown that anodized titanium and its alloys with a thin film of anatase (TiO(2)) on its surface can inhibit attachment of Pseudomonas sp. when illuminated with near-UV light (350 - 380 nm). In the present study, a comparison of the photocatalytic inhibition of microbial attachment on titanium surfaces anodized at different voltages was carried out. Thin films of anatase of varying thickness were produced on titanium grade-2 by anodizing in dilute orthophosphoric acid solution at 30 V, 50 V and 100 V. The photocatalytic efficiency of these anodized surfaces was measured by the methylene blue degradation method. The anodised surfaces were exposed to liquid cultures of Gram-negative Pseudomonas sp., Gram-positive Micrococcus sp. and to a mixed algal culture. Photocatalytic inhibition of microbial attachment was maximum on the titanium surface anodized at 30 V, followed by the surface anodized at 50 V and then at 100 V. The photocatalytic inhibition of microbial attachment was also found to be dependent on the cell wall characteristics of the organism. The Gram-negative Pseudomonas sp. with a lipoproteinaceous outer membrane was the most susceptible to the photocatalytic effect, while the Gram-positive Micrococcus sp. with peptidoglycan cell wall showed moderate susceptibility and the algae with siliceous cell wall showed no susceptibility at all.