Biosynthesis of silver nanoparticles using Aspergillus flavus and investigation of some effective factors on its production

 Using fungi as sources of enzymes that can catalyze specific reactions conducing to inorganic nanoparticles, is being developed. Aspergillus flavus has a great potential in extracellular biosynthesis of silver nanoparticles. Since this fungus can grow on simple media quickly and adequately, it is cheaper to use it in silver nanoparticles biosynthesis than other methods. Extracellular biosynthesis of silver nanoparticles was carried out by adding 1mM silver nitrate to A. flavus cell filtrate. Nanoparticles production was confirmed by visual observation of color change in the cell filtrate and UV-vis spectrophotometry. More investigation was conducted using XRD, FTIR and TEM. The stability of nanoparticles and the effect of culture media and silver nitrate concentration on nanoparticles’ production were studied too. The color change of cell filtrate from pale to brown confirmed the extracellular production of silver nanoparticles. The absorption spectra indicated a peak at 420nm attributable to the sliver nanoparticles. X-ray diffraction showed crystalline nature of the biosynthesized nanoparticles. Characterization of sliver nanoparticles’ shape and size using TEM showed that they were spherical and 18.2 nm in diameter. These nanoparticles were stable for 11 months and FTIR demonstrated the presence of proteins as capping agents which lead to their stability. More silver nitrate caused more nanoparticles production and PDB was the best media in this process. Biosynthesized nanoparticles were crystalline in nature, small in size and monodispersed. Besides, they were very stable due to capping by fungal secreted proteins; this stability is reported for the first time in the world. The fungal-mediated green and ecofriendly approach towards the synthesis of nanoparticles can be used as an alternative to the more popular physical and chemical methods for the synthesis of nanoparticles