Extracellular biosynthesis of silver nanoparticles by culture supernatant of Pseudomonas aeruginosa

The development of reliable, eco-friendly processes for the synthesis of nanoscale materials is an important aspect of nanotechnology. Silver bionanoparticles have been known to have inhibitory and bactericidal effects. In the present study, authors report the extracellular synthesis of nanoparticles of silver by reduction of aqueous Ag+ ions with the culture supernatant of Pseudomonas aeruginosa. It was found that aqueous Ag+ ions in solution when exposed to P. aeruginosa get reduced, thereby leading to the formation of silver nanoparticles. The formation of silver nanoparticles was confirmed by the change in colour of the culture filtrate from yellow to reddish brown after the addition of silver nitrate. The morphology and uniformity of silver nanoparticles were investigated by UV-Vis spectroscopy, X-ray diffraction and scanning electron microscope (SEM). The interaction between protein and silver nanoparticles was analyzed using FTIR. The process of reduction was extracellular, which makes it an easier method for the synthesis of silver nanoparticles. These biosynthesized silver nanoparticles were also evaluated for their antimicrobial activities against Escherichia coli and Vibrio cholerae.