Green Synthesis, Characterization and In Vitro Antimicrobial Activity of Silver Nanoparticles (AgNPs) Using Fungal Aqueous Extract

Research in green synthesis of metallic nanoparticles and their applications in engineering, food, biomedicine and agriculture is growing rapidly. The presence of biologically active metabolites in fungi makes them ideal candidates for green synthesis of silver nanoparticles (AgNPs). This study aims at discerning an emerging applicability of a basidiomycete mushroom, Phaeolus schweinitzii, for mycosynthesis of AgNPs and their antimicrobial properties. The colour change in P. schweinitzii aqueous extract was used to detect and curate the synthesis of AgNPs. The AgNP surface plasmon resonance (SPR) was observed in the visible spectra at approximately 428 nm using UV-Vis spectroscopy. The XRD spectrum revealed a face-centered cubic (FCC) structure of AgNPs with an average crystallite size of 38.78 nm. FT-IR manifested various functional clusters of biomolecules which were involved in bioreduction, capping and stabilization of AgNPs. FE-SEM imaging of AgNPs revealed a spherical shape with an average size of 88.65 nm. The synthesized AgNPs showed strong antimicrobial activities against Salmonella gallinarum, E. coli, Staphylococcus aureus, Aspergillus niger and Fusarium oxysporum with varying zones of inhibition at different concentrations. The highest concentration (5 mg/ml) of AgNPs produced a maximum zone of inhibition (13.33 +/- 0.57 mm) against gram negative bacteria (Salmonella gallinarum and E. coli) and lowest (11.66 +/- 0.57 mm) against gram positive bacteria (Staphylococcus aureus). The study also revealed that synthesized AgNPs showed comparatively higher antifungal activity than the positive control (nystatin). The findings from this study explicitly concur with the ever-relevant use of biogenic AgNPs against various pathogenic microorganisms.