Hydrothermal assisted biosynthesis of silver nanoparticles from Streptomyces sp. GUT 21 (KU500633) and its therapeutic antimicrobial activity

In the present investigation we report unique biological green synthesis of nanoparticles (AgNPs) by secondary metabolites of Streptomyces supernatant extract acting as reducing agents in hydrothermal process. Various divergent techniques like sonication, microven, heating and hydrothermal (autoclaving) techniques were employed to produce silver nanoparticles through microbe-mediated assistance. The Streptomyces sp. GUT 21 was isolated from the field soil sampled neighbouring the campus of Gulbarga University. Morphological and biochemical characterization of the strain was performed and its taxonomical genus identification was determined by 16s rDNA technique. The formation of nanoparticles was first monitored by measuring the surface plasmon resonance (SPR) band at 410 nm through UV–Visible absorption spectroscopy. FTIR analysis revealed that many efficient clusters of functional biomolecules are playing significant role in capping and synthesis process during hydrothermal method. The crystalline structure of the AgNPs and the presence of elemental silver nanoparticles were confirmed by powder X-ray diffraction (PXRD) and scanning electron microscopy. Our results indicated that, nanoparticles are spherical in shape with an average of 23–48 nm in size. The biosynthesized AgNPs exhibited significant antibacterial activity against Escherichia coli (MTCC 9537), Klebsiella pneumoniae (MTCC 109), Pseudomonas aeruginosa (MTCC1688) and Staphylococcus aureus (MTCC 96). This biotechnological development of synthesis of nanoparticles can further be exploited as ‘‘new-generation of antimicrobials’’ against multi-drug resistant bacteria (MDR) for various medical diagnostic applications.