The bactericidal effect of TiO2 photocatalysis involves adsorption onto catalyst and the loss of membrane integrity.

The bactericidal effect of photocatalysis with TiO2 is well recognized, although its mode of action is still poorly characterized. It may involve oxidation, as illuminated TiO2 generates reactive oxygen species. Here we analyze the bactericidal effect of illuminated TiO2 in NaCl-KCl or sodium phosphate solutions. We found that adsorption of bacteria on the catalyst occurred immediately in NaCl-KCl solution, whereas it was delayed in the sodium phosphate solution. We also show that the rate of adsorption of cells onto TiO2 is positively correlated with its bactericidal effect. Importantly, adsorption was consistently associated with a reduction or loss of bacterial membrane integrity, as revealed by flow cytometry. Our work suggests that adsorption of cells onto aggregated TiO2, followed by loss of membrane integrity, is key to the bactericidal effect of photocatalysis.

[1]  Jeyong Yoon,et al.  Different Inactivation Behaviors of MS-2 Phage and Escherichia coli in TiO2 Photocatalytic Disinfection , 2005, Applied and Environmental Microbiology.

[2]  Cesar Pulgarin,et al.  Effect of pH, inorganic ions, organic matter and H2O2 on E. coli K12 photocatalytic inactivation by TiO2: Implications in solar water disinfection , 2004 .

[3]  J. Tay,et al.  Photocatalytic degradation of E. coliform in water. , 2003, Water research.

[4]  M. Litter,et al.  Photocatalytic bactericidal effect of TiO2 on Enterobacter cloacae: Comparative study with other Gram (−) bacteria , 2003 .

[5]  Kayano Sunada,et al.  Studies on photokilling of bacteria on TiO2 thin film , 2003 .

[6]  O. González Díaz,et al.  TiO2-photocatalysis as a tertiary treatment of naturally treated wastewater , 2002 .

[7]  John A. Byrne,et al.  The photocatalytic removal of bacterial pollutants from drinking water , 2002 .

[8]  Alessandra Ghiani,et al.  Resolution of Viable and Membrane-Compromised Bacteria in Freshwater and Marine Waters Based on Analytical Flow Cytometry and Nucleic Acid Double Staining , 2001, Applied and Environmental Microbiology.

[9]  J. Araña,et al.  The photocatalytic disinfection of urban waste waters. , 2000, Chemosphere.

[10]  M. Labra,et al.  Two and three-color fluorescence flow cytometric analysis of immunoidentified viable bacteria. , 2000, Cytometry.

[11]  D. Hesse,et al.  Parameters Influencing Photoassisted Adsorption of NO on TiO2 Powder , 2000 .

[12]  M. Nieuwenhuijsen,et al.  Chlorination disinfection byproducts in water and their association with adverse reproductive outcomes: a review , 2000, Occupational and environmental medicine.

[13]  Edward J. Wolfrum,et al.  Bactericidal Activity of Photocatalytic TiO2 Reaction: toward an Understanding of Its Killing Mechanism , 1999, Applied and Environmental Microbiology.

[14]  H. Y. Chen,et al.  Inhibition of the adsorption and photocatalytic degradation of an organic contaminant in an aqueous suspension of TiO2 by inorganic ions , 1997 .

[15]  J. Yates,et al.  Photocatalysis on TiO2 Surfaces: Principles, Mechanisms, and Selected Results , 1995 .

[16]  Z. Zainal,et al.  Bactericidal Activity of TiO2 Photocatalyst in Aqueous Media: Toward a Solar-Assisted Water Disinfection System. , 1994, Environmental science & technology.

[17]  R. Clark,et al.  Inactivation of Escherichia coli by titanium dioxide photocatalytic oxidation , 1993, Applied and environmental microbiology.

[18]  T. Saito,et al.  Mode of photocatalytic bactericidal action of powdered semiconductor TiO2 on mutans streptococci. , 1992, Journal of photochemistry and photobiology. B, Biology.

[19]  T. Nakajima,et al.  Photoelectrochemical sterilization of microbial cells by semiconductor powders , 1985 .

[20]  T. A. Bellar,et al.  The Occurrence of Organohalides in Chlorinated Drinking Waters , 1974 .

[21]  G. C. Miller,et al.  Photocatalytic inactivation of coliform bacteria and viruses in secondary wastewater effluent , 1995 .

[22]  齋藤 俊行.  Mode of photocatalytic bactericidal action of powdered semiconductor TiO[2] on mutans streptococci , 1991 .

[23]  B. Bachmann,et al.  Derivations and genotypes of some mutant derivatives of Escherichia coli K12 , 1987 .

[24]  J. Rook.  Formation of Haloforms during Chlorination of natural Waters , 1974 .

[25]  J. Lichtenberg,et al.  THE OCCURRENCE OF ORGANOHILDES IN CHLORINATED DRINKING WATER , 1974 .