Biosynthesis, optimization and characterization of silver nanoparticles using a soil isolate of Bacillus pseudomycoides MT32 and their antifungal activity against some pathogenic fungi

Abstract

Optimization of some experimental growth conditions for biosilver nanoparticles synthesized using supernatant of Bacillus pseudomycoides MT32 were studied. The optimized growth conditions were obtained at 2mM silver nitrate concentration, 30°C temperature degree, 6.5 pH level, 40 h incubation time, 140 rpm agitation speed, medium type was Nutrient broth (NB) and supernatant and silver nitrate ratio was 20:30. Characterizations of the produced nanoparticles were done using seven advanced instruments. The ultraviolet-visible spectrashowed an absorption peak at 420 nm. Transmission Electron Microscopy (TEM) showed that the mean diameter of the formed SNPs was 25 to 43 nm. Powder X-ray diffraction (XRD) revealed that the particles are crystalline in nature, with a spherical structure and their size ranges from 32 to 86 nm. From dynamic light scattering (DLS) and Zeta potential analyses, the average SNPs size was 63.39 nm and the Zeta potential was -18.3 mV. Energy-dispersive X-ray spectroscopy (EDX) exhibited strong signal in the silver region and confirmed the formation of SNPs. The SNPs also exhibited traces of agglomeration. From antifungal studies in vitro, the produced SNPs are capable of suppression, in different extents, of ten commercially plant pathogenic fungi and the recorded values of MIC and MFC were varied due to the type of fungi used, and they were in a range of 70 - 90, and 75 - 100 μg / l, respectively. The antifungal activity of the SNPs produced by Bacillus pseudomycoides MT32 is useful in solving different problems in crops production as well as in animals' nutrition.