Characterization and antimicrobial activity of silver nanoparticles synthesized by rice straw utilizing bacterium (Lysinibacillus fusiformis)

Use of microorganisms in synthesis of silver nanoparticles (AgNPs) is coast effective and eco-friendly and easily scaled up for large scale synthesis. The present investigation reports a simple and environmental friendly method for biological synthesis of silver nanoparticles (AgNps) by Lysinibacillus fusiformis strain AUMC b-160 which was isolated from soil sample treated with manure and showed ability to utilize wheat and rice straws as a sole carbon source. The bacterium has been identified molecularly by partial sequencing of the 16s rDNA gene (approximately 1100 bp) and the result demonstrate 99% homology to Lysinibacillus fusiformis. Furthermore, the nucleotide sequence deposited in the GenBank under accession number. The biosynthesized nanoparticles are characterized by the UV-Vis spectroscopy that revealed the characteristic surface plasmon resonance band centered at 425 nm. Transmission electron microscopy (TEM) analysis confirmed the formation of varying morphology silver particles in the size range from 10-22 nm. FTIR confirmed that the synthesized nanoparticles are surrounded by proteins and metabolites and the stability of silver nanoparticles are due to proteins and enzymes coated them. Also the study was designed to compare the in vitro antimicrobial effect of biological silver nanoparticles against human pathogenic bacteria and Candida. It was found that the growth of all using bacteria and Candida was inhibited by the biosynthesized silver nanoparticles.