Silver nanoparticles from Lactobacillus Delbrueckii: Microbial synthesis, characterization and antibacterial activity

Abstract

Microbial synthesis of nanoparticles is an eco-friendly and non-toxic method of synthesizing silver nanoparticles. Biological synthesis of silver nanoparticles (SNPs) has become a focus of current interest due to their unique properties, thus serving as alternative to chemical and physical methods. This study aimed to investigate the potential of Lactobacillus delbrueckii for the synthesis of SNPs and their antibacterial activities against pathogens. SNPs were synthesized by L. delbrueckii culture free supernatant and characterized using visual detection, UV-visible spectroscopy, fourier transformed infra-red spectroscopy (FTIR) and scanning electron microscopy (SEM). Antibacterial activity of the biosynthesized SNPs was estimated using agar well method. Biosynthesized SNPs were characterized by a strong plasmon resonance peak at 550 nm and had a broad band between 450 – 650 nm. There were colour changes from yellow to golden brown. FTIR confirmed the presence of hydroxyl, aldehyde, carboxylic acid, amino acid, and esters which are responsible for the stability of silver nanoparticles. Morphologically, biosynthesized nanoparticles were spherical with size range of 1.7 - 10 nm. The biosynthesized SNPs exhibited the highest antibacterial activity with significant inhibitory effects against both Gram positive and Gram negative bacteria, when compared to ciprofloxacin and the culture free supernatant of L. delbrueckii.