Green synthesis of nanosilver particles by Aspergillus terreus HA1N and Penicillium expansum HA2N and its antifungal activity against mycotoxigenic fungi.

Abstract

The aim of this study was to synthesize silver nanoparticles (AgNPs) by an eco-friendly and low-cost method using the fungi Aspergillus terreus HA1N and Penicillium expansum HA2N as an alternative to chemical procedures mostly requiring drastic experimental conditions emitting toxic chemical byproducts. Also, this study has been extended to evaluate the effect of AgNPs on the growth of some mycotoxigenic fungi and ochratoxin A (OTA) produced by Aspergillus ochraceus. The AgNPs have been characterized by UV-Visible Spectrophotometer, Dynamic Light Scattering (DLS), Fourier Transform Infrared Spectroscopy (FTIR) and Transmission Electron Microscope (TEM). The TEM analysis has revealed that the size of AgNPs ranged between 14 and 25nm in the case of P.expansum and 10-18nm in the case of A.terreus. The antifungal activity of AgNP colloids has indicated that the highest inhibition zone was detected with AgNPs synthesized by A.terreus HA1N against all tested fungi. The highest inhibition zone was detected with Aspergillus niger at concentrations 3 and 6μg of AgNP solution (7·56±0·38 and 11·3±1·8mm, respectively) while, A.ochraceus showed the maximum inhibition zone (16·33±0·96mm) at the concentration 9μg of AgNPs synthesized by A.terreus. The results have also indicated that the AgNPs synthesized by A.terreus and P.expansum at the concentration 220μg/100ml media gave the highest reduction of OTA, where the percentages of reduction were 58·87 and 52·18% respectively. The smallest size AgNPs synthesized by A.terreus HA1N are better in their antifungal activity against all tested mycotoxigenic fungi than the largest one synthesized by P.expansum HA2N. This is the first study focused on using AgNPs in control of OTA production.