Takemi Oketa

Inactivation Mechanism of Microorganisms by the Synergy of Silver and Light Irradiation, and the Application in Household Electrical Appliances

The inactivation efficiencies of microorganisms were found to be enhanced by using silver solution together with ultraviolet light (UV-A, 395 nm) irradiation. The inactivation efficiencies were improved remarkably especially in eukaryotic microorganism. To make clear the inactivation mechanism of microorganisms by the combination effect of silver and ultraviolet light irradiation, the resultant solution was characterized by ESR (Electron spin resonance, ESR). Scanning electron microscopy (SEM) and the methnd for measuring enzyme activity of mitochondria for eukarvotic cells were used to conjecture the mechanism, by analysis of the morphological and physiologic changes in eukaryotic cells. It is proposed that silver oxide (Ag20) can be activated by ultraviolet light irradiation and react with water molecules to produce hydroxyl radical (.OH). Hydroxyl radical could damage cell wall of eukaryotic microorganisms, and inactivate the enzyme activity of mitochondria of eukaryotic microorganism cells. Accordingly, eukaryotic microorganism cells would die. In the experiment, Staphylococcus aureus was employed as the representative of prokaryotic microorganisms, and Candida albicans and Trichophyton mentagrophytes as the representative of eukaryotic microorganisms, respectively. Moreover, the results of the technology applied to washing machine were presented and discussed.