Biosynthesis, Characterization and Optimization of Silver Nanoparticles Using Exopolysaccharide from Pleurotus SP

An environmentally, sustainable and feasible bottom-up approach was utilized for the biosynthesis of silver nanoparticles using exopolysaccharide (EPS) secreted by Pleurotus tuber-regium (Fr.) Singer which is a tropical perennial edible and medicinal mushroom. Mycochemical assay showed positive presence of saponin and steroid. Silver nanoparticles (AgNPs) were biosynthesized using EPS as reducing capping and stabilizing agent. Imperative operational parameters vis-à-vis concentration, contact time, reaction temperature and volume ratio were investigated. 10 mM silver nitrate, 180 hours, 100°C and 50:50 were found to be the optimal parameters for silver nanoparticle production. The biosynthesized AgNPs were characterized using Ultraviolet-visible (UV-Vis) spectroscopy and Fourier Transform Infrared (FTIR). The Surface Plasmon Resonance (SPR) band was observed at 420 nm characteristic region of AgNPs. Mycochemical screening and FTIR spectroscopy revealed the presence of phytomolecules and prominent peaks of polyols responsible for the reduction of Ag
⁺
and Ag
⁰
. The AgNPs as well as the exopolysaccharide produced were tested against important fruit spoilage microorganisms (Aspergillus niger, Aspergillus flavus, Rhizopus stolonife, Fusarium sp.). The nanoparticles at 200 μL/mL and 100 μL/mL were found to inhibit all the target fungi. Rhizopus stolonifer and Fusarium sp. were more sensitive at 50 μL/mL and 25 μL/mL concentrations of both the silver nanoparticles and EPS. Based on the study, it can be inferred that silver nanoparticles capped with EPS and EPS have antifungal property.