Extracellular synthesis of silver nanoparticles using four fungal species isolated from lichens

Extracellular biosynthesis of silver nanoparticles using five fungal species including Fusarium oxysporum and four others isolated from native lichens (Kerman, Iran) was investigated in this study. These fungal species were identified as Arctoparmelia incurva, Penicillium chrysogenum, Uncultured root-associated fungus, and Caloplaca arnoldii by using ITS rRNA sequence analysis. These species were then cultivated in four common industrial wastes, namely a combination of yeast and malt extract, sugar beet molasses, whey, and wastewater of beverage industry, prior to their use for biosynthesis. The synthesis of the nanoparticles was monitored by UV-visible spectroscopy. It was found to be significantly affected by both fungal species and their cultivation media. C. arnoldii cultivated in the yeast and malt extract resulted in the best performance regarding reaction kinetics, particle mean diameter and size distribution. The mean diameter and variance of the nanoparticles were determined to be about 11nm and 24 by using transmission electron microscopy and powder X-ray diffraction techniques, respectively. The zeta potential of the nanoparticles was measured to be -21.5mV confirming their long-term stability. These findings suggest a new biosynthetic route towards eco-friendly and inexpensive production of the nanoparticles in bulk.