Bacterial Synthesis of Silver Nanoparticles by Culture Free Supernatant of Lactic Acid Bacteria Isolated from Fermented Food Samples

Aim: Biosynthesis of silver nanoparticles (SNPs) using culture free supernatant (CFS) of Lactic acid bacteria (LAB).

Study Design: To biosynthesize, characterize and to determine the antibacterial potential of silver nanoparticle using culture free supernatant of lactic acid bacteria and to determine the effect of some parameters on SNPs biosynthesis.

Methodology: Biosynthesis and characterization of SNPs using CFS of LAB and the antibacterial activity.

Place and Duration of Study: Department of Microbiology, University of Ibadan, Ibadan, Oyo state, Nigeria between Jan to October 2016.

Results: The antibacterial potential of the CFS from the LABs was evaluated on some pathogenic bacteria and antibacterial activity ranged from 0 – 20 mm. The two LAB strains LPW2 and LPF6 had 93% and 86% relatedness to Lactobacillus casei strain WK2G-3A and Lactobacillus fermentum strain E10-15. The CFS of the LAB strains and AgNO3 was able to produce SNPs. The biosynthesized SNPs had a strong Surface Plasmon Resonance (SPR) peak at 500 nm, varying shape (partially aggregated particles) and the sizes ranged from 0.7 - 10.0 nm and 1.4 – 10.0 nm for CFS SNPs from Lactobacillus casei and Lactobacillus fermentum. Carboxylic acid, protein, aldehydes, ester and hydroxyl groups are the functional groups responsible for SNPs formation. The antibacterial activity of the SNPs ranged from 11 – 29 mm. Bacillus sp. and Streptococcus pyogenes were found to be more susceptible to the biosynthesized SNPs. 28°C, pH 4 and 10 Mm AgNO3 supported the highest SNPs production.

Conclusion: In conclusion the CFS from the LABs biosynthesized SNPs which exhibited antibacterial activity against some pathogenic microorganisms.