Identifying the role of reactive oxygen species (ROSs) in Fusarium solani spores inactivation

Abstract

The inactivation mechanism of photocatalytic disinfectants on bacteria is well known. In contrast, the potential inactivation of fungal spores by visible-light induced photocatalysis has been recognized, but the inactivation mechanism is poorly understood. We hypothesize that photocatalytically generated reactive oxygen species (ROSs) are directly involved in this mechanism. To test this hypothesis, we identified the roles of ROSs in the inactivation of Fusarium solani spores. As the photocatalysts, we doped TiO2 with 3 typical dopants, forming Ag/TiO2, N/TiO2 and Er3+:YAlO3/TiO2. The Ag/TiO2 photocatalysis was dominated by H2O2, with the longest lifetime among the investigated ROSs. Ag/TiO2 photocatalysis yielded almost 100 % inactivation efficiency and preserved the cell-wall shape of the spores, thus minimizing the biomolecule leakage. Er3+:YAlO3/TiO2 was dominated by h+ ROSs, yielding an inactivation efficiency of 91 %; however, the severe leakage released large numbers of molecular bio-products. Severe damage to the cell walls by the h+ species was confirmed in micrograph observations. Subsequent to cell wall breakage, the Er3+:YAlO3/TiO2 nanoparticles entered the spore cells and directly oxidized the intracellular material. The N/TiO2 photocatalysis, with •O2− dominated ROSs, delivered intermediate performance. In conclusion, photocatalysts that generate H2O2-dominated ROSs are most preferred for spore inactivation.