Porphyrin-Photosensitized Processes: An Environmentally Friendly Approach to Water Disinfection

Waterborne diseases are characterized by an increased frequency and poorly efficacious treatment approaches owing to the variety of pathogenic agents and the development of resistance to chemical or physical strategies for water disinfection. Our groups are testing the potential of photodynamic processes promoted by porphyrins bound to inert supports which allow an efficient recovery and reuse of the photosensitizer and prevent its direct interaction with normal components of the ecosystems, as well as its diffusion in the environment. Thus, we investigated the sensitivity of a Gram-positive bacterium (meticillin-resistant Staphylococcus aureus) and a Gram-negative bacterium (Escherichia coli) to irradiation with visible light in the presence of a tetracationic porphyrin, meso-tri(N-methyl-pyridyl), mono(N-dodecyl) porphine (C12) associated with different resins. The efficiency of the photosensitized antibacterial effect was found to be largely influenced by the nature of the carrier. Thus, by using milligrams of porphyrin bound to carboxymethyl-cellulose and relatively low-intensity visible light, an extensive (up to 5−6 log) decrease in the bacterial population after 1 h incubation and a 30 min irradiation was observed. These results yield promising novel perspectives for further developing such porphyrin-photosensitized processes into a flexible and valuable technique for environmentally friendly treatment of microbiologically polluted aquaculture systems.