Visible-light-driven photocatalytic disinfection of Aspergillus fumigatus under germinative biomorph: Efficiency and mechanism

Abstract

The photocatalytic disinfection efficiency of fungi spores, especially Aspergillus spores, is much lower compared with bacteria and virus, particularly under visible light. It is quite necessary to develop new strategies and explore the mechanism for enhanced the visible-light-driven photocatalytic disinfection of Aspergillus spores. In this work, the visible-light-driven photocatalytic disinfection of Aspergillus fumigatus spores (a common Aspergillus species) under different biomorph were analysed by the prepared photocatalysts, such as g-C3N4 nanosheet, bulk Bi4O7, and g-C3N4/Bi4O7. When the A. fumigatus spores were under dormant biomorph, the prepared photocatalysts revealed barely photocatalytic disinfection efficiency. Whereas the A. fumigatus spores germinated (that is swelling and germination), the photocatalytic disinfection efficiency was remarkably enhanced. About 81% of the germinated A. fumigatus spores were inactivated by the optimal g-C3N4/Bi4O7-40 (the initial concentration is 1 × 104 CFU/mL). During the photocatalytic disinfection, the superoxide radicals (O2−), hydroxyl radicals (OH) were the prominent active constituents which were formed by the adsorbed oxygen and the adsorbed H2O. When the A. fumigatus spores were under dormant biomorph, the dense and complex cell wall could well protect from O2− and OH attacked. Significantly, when the A. fumigatus spores were under germinative biomorph, the double-layered cell wall remodeled and the metabolism accelerated which brought about the frequent exchange of substances between intracellular and extracellular. O2− and OH could likely interact with the germinated A. fumigatus spores, and decompose the cell wall and cytoplasm.