Inhibitory Activities and Characterization of Greenly Synthesized Silver Nanoparticles using Culture Free Supernatant of Lactobacillus plantarum

Abstract

This study is aimed at the biosynthesis, characterization and inhibitory activity of silver nanoparticles using L. Plantarum culture free supernatant (CFS). Silver nanoparticles (SNPs) were biosynthesized by L. plantarum and characterized using Visual detection, UV-Visible spectroscopy, Fourier Transformed Infra-red spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). The effect of the cultivation conditions on the biosynthesis of SNPs was carried out. Antibacterial activity of the biosynthesized silver nanoparticles by L. plantarum was done using agar well method. Biosynthesis of SNPs by L. plantarum was characterized by a strong plasmon resonance peak at 450 nm and a broad band at 350 - 550 nm. There were colour changes from yellow to brown. FTIR confirmed the presence of hydroxyl, aldehyde, carboxylic acid, amino acid, and esters which are responsible for the stability of silver nanoparticles (SNPs). The shape of the biosynthesized nanoparticles was spherical and partially aggregated with particle size ranging from 0.7- 10.0 nm. The antibacterial activity of the synthesized SNPs by L. plantarum (LPSNPs) ranged from 14 – 22 mm. Staphylococcus aureus and Escherichia coli were more susceptible to the synthesized SNPs. 24 hr incubation time, 25^oC, pH 9 and 5 mM gave the best SNPs production. The culture free supernatant of L. plantarum can be used for the synthesis of SNPs with highly effective antibacterial activities.