Comparative characterization of silver nanoparticles synthesized by spore extract of Bacillus subtilis and Geobacillus stearothermophilus

Abstract

Objective(s): Silver nanostructures have gathered remarkable attention due to their applications in diverse<br />fields. Researchers have recently demonstrated that bacterial spores are capable of reducing silver ions to<br />elemental silver leading to formation of nanoparticles.<br />Materials and Methods: In this study, spores of Bacillus subtilis and Geobacillus stearothermophilus were<br />employed to produce silver nanoparticles (SNPs) from silver nitrate (AgNO3) through a green synthesis<br />method. The production of SNPs by spores, heat inactivated spores (microcapsule) and spore extracts was<br />monitored and compared at wavelengths between 300 to 700 nm. The biosynthesized SNPs by spore extracts<br />were characterized and confirmed by XRD and TEM analyses.<br />Results: UV-Visible spectroscopy showed that the spore extracts were able to synthesize more SNPs than<br />the other forms. The XRD pattern also revealed that the silver nanometals have crystalline structure with<br />various topologies. The TEM micrographs showed polydispersed nanocrystal with dimensions ranging from<br />30 to 90 nm and 15 to 50 nm produced by spore extracts of B. subtilis and G. stearothermophilus, respectively.<br />Moreover, these biologically synthesized nanoparticles exhibited antimicrobial activity against different<br />opportunistic pathogens.<br />Conclusion: This study suggests the bacterial spore extract as a safe, efficient, cost effective and eco-friendly<br />material for biosynthesis of SNPs.