Solubilization and bioprecipitation of zinc oxide nanoparticles by fungi isolated from zinc sulfide mineral ores

Abstract

Zinc oxide (ZnO) is an insoluble form, which often means less bioavailable to the organisms. Seven fungal isolates were isolated from zinc sulfide mineral ores (sphalerite) and obtained from Padaeng Industry in Tak province, Thailand. They were examined for the ability to solubilize and precipitate zinc oxide nanoparticles. Fungal isolates were grown on potato dextrose agar (PDA) medium supplemented with 0.5% (w/v) zinc oxide nanoparticles. Among tested fungal strains, Aspergillus Niger showed the highest efficiency for solubilizing zinc oxide nanoparticles. Biomineral crystals were observed in zinc oxide nanoparticles-containing agar medium underneath colonies of Aspergillus Niger. Scanning electron microscope (SEM) equipped with energy dispersive X-ray spectrometer (EDS) and X-ray powder diffraction (XRPD) studies revealed that the biomineral crystals are zinc oxalate hydrate (C2O2Zn•2H2O). It would be suggested that this fungal strain has potential biotechnological application in agricultural practice and heavy metal bioremediation.