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International Journal of Environment Science and Technology
Center for Environment and Energy Research and Studies (CEERS)
ISSN: 1735-1472
EISSN: 1735-2630
Vol. 12, No. 1, 2015, pp. 61-72
Bioline Code: st15006
Full paper language: English
Document type: Research Article
Document available free of charge

International Journal of Environment Science and Technology, Vol. 12, No. 1, 2015, pp. 61-72

 en The hybrid methylene blue–zeolite system: a higher efficient photocatalyst for photoinactivation of pathogenic microorganisms
Smolinská, M.; Čík, G.; Šeršeň, F.; Čaplovičová, M.; Takáčová, A. & Kopáni, M.

Abstract

The composite system can be prepared by incorporation of methylene blue (MB) into the channels of zeolite and by adsorption on the surface of the crystals. The composite photosensitizer effectively absorbs the red light (λmax = 648 nm) and upon illumination with light-emitting diode at a fluence rate of 1.02 mW cm-2 generates effectively reactive singlet oxygen in aqueous solution, which was proved by EPR spectroscopy. To test efficiency for inactivation of pathogenic microorganisms, we measured photokilling of bacteria Escherichia coli check for this species in other resources and Staphylococcus aureus check for this species in other resources and yeasts Candida albicans check for this species in other resources . We found out that after the microorganisms have been adsorbed at the surface of such modified zeolite, the photogenerated singlet oxygen quickly penetrates their cell walls, bringing about their effective photoinactivation. The growth inhibition reached almost 50 % at 200 and 400 mg modified zeolite in 1 ml of medium in E. coli and C. albicans, respectively. On the other hand, the growth inhibition of S. aureus reached 50 % at far smaller amount of photocatalyst (30 μg per 1 ml of medium). These results demonstrate differences in sensitivities of bacteria and yeast growth. The comparison revealed that concentration required for IC50 was in case of C. albicans several orders of magnitude lower for a zeolite-immobilized dye than it was for a freely dissolved dye. In S. aureus, this concentration was even lower by four orders of magnitude. Thus, our work suggested a new possibility to exploitation of zeolite and MB in the protection of biologically contaminated environment, and in photodynamic therapy.

Keywords
Disinfection; Light-emitting diode; Modified zeolite; Pathogens; Photodynamic effect; Singlet oxygen

 
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