Nanosilver Fabrication Mediated by Exopolysaccharides from Pseudomonas fluorescens and Its Biological Activities

Synthesis of silver nanoparticle (SNP) has become an emerging trend in the field of nanotechnology. Here a greener method was approached to develop silver nanoparticles using extracted exopolysaccharides (EPS) from Pseudomonas fluorescens, a soil isolate from rhizosphere of the medicinal plant, Catharanthus roseus. The exopolysaccharide acted as a reducing and stabilizing agent in converting silver nitrate to silver nanoparticles. The fabricated SNPs were characterized by UV-Visible Spectroscopy, Scanning Electron Microscopy (SEM) and FT-IR Spectroscopy. The FT-IR analysis revealed that proteins present in the polysaccharide served as a capping agent. This simple process was carried out for 5 days at room temperature at optimum pH 7. The dried SNP sample is found to be stable for more than 6 months. The present work also focused on SNPs’ antimicrobial effect by agar well diffusion technique and antioxidant activity by DPPH method. The EPS reduced SNP was found to be more active against Gram negative than Gram positive and also worked in inhibiting Candida sp. DPPH radical scavenging effect of SNP was highly effective than standard at a maximum concentration of 1mg/ml. The investigation thus showed that EPS stabilized SNP could be employed in several pharmaceutical purposes.