Biogenic synthesis of silver nanoparticles using Jatropha curcas seed cake extract and characterization: evaluation of its antibacterial activity

Nanoparticles synthesis using biological methods is gaining importance over the physicochemical methods because of its nontoxic nature and less environmental burden. In this paper, we report the biosynthesis of silver nanoparticles (AgNPs) from its precursor salt AgNO_3, using Jatropha curcas seed cake extract, which will provide value addition to the byproduct of the biodiesel industry. Jatropha curcas seed oil is usually used as a source for biodiesel production as fatty acyl methyl esters (FAME). Jatropha curcas seed cake extract was screened for phytochemicals present in it which may help in reducing the precursor metal salt to nanoparticles as well as coat around the nanoparticles, thereby increasing their stability. Phytochemical screening revealed the presence of carbohydrates, proteins, alkaloids, flavonoids, saponins, tannins, phenols and terpenoids in the extract. Biosynthesized nanoparticles were characterized by UV-visible spectroscopy, SEM and FTIR. The Uv-visible spectroscopic analysis confirmed the production of silver nanoparticles at 400–460 nm, where the colour change in the solution from pale yellow to brown indicated the formation of silver nanoparticles. SEM image showed the size of the AgNPs ranged from 80 nm to 95 nm. FTIR analysis confirmed the capping of nanoparticles with organic residues like, proteins, amino acids, and polyphenols present in the extract, which led to increased stabilization of nanoparticles. Negative zeta values indicated the stability of nanoparticles. The synthesized AgNPs were tested for their antibacterial activity against both Gram positive (Bacillus subtilis) and Gram negative (E. coli, Pseudomonas aeruginosa) bacteria with known antibiotic as a control. Biosynthesized AgNPs showed significantly high bacteriostatic effect.