Green Synthesis of Silver Nanoparticles Using Supernatant from Lactobacillus casei LPW2 Cultured in Modified Exopolysaccharides Selection Medium

Aim: Biosynthesis of silver nanoparticle using supernatant from L. casei cultured in modified exopolysaccharide selection medium.

Study Design: To bio-reduced AgNO3 using supernatant from L. casei cultured in modified exoploysaccharides selection medium and to evaluate the antibacterial potential of the biosynthesized SNPs.

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

Methodology: Production and characterization of SNPs using supernatant from L. casei cultured in modified Exopolysaccharides selection medium and to evaluate the antibacterial activity of the SNPs.

Results: Nanotechnology has to do with the manufacture of materials at the nanometer level. Clusters of atoms in the size range of 1 – 100 nm are known as nanoparticles. Biosynthesis of silver nanoparticles (SNPs) using supernatant of lactic acid bacteria (LAB) culture in modified Exopolysaccharides selection medium (mESM) was investigated. The supernatant obtained from L. casei LPW2 cultured in modified exopolysaccharides selection medium was used in the bio-reduction of AgNO3. The reaction mixture turned deep brown after 24 hrs of incubation indicating the formation of SNPs. The SNPs was characterized with UV-Visible spectrophotometer and it had a broad band between 400 – 600 nm with strong surface plasmon resonance at 500 nm. The FTIR analysis revealed the presence of carboxylic acids, hydroxyl group, amino acids and protein as the possible functional groups responsible for the bioreduction of silver to its nanoparticles. The antibacterial potential of the SNPs was evaluated and the zone of inhibition ranged from 13 – 24 mm with Bacillus sp. being the most susceptible. The minimum inhibitory concentration (MIC) of the biosynthesized SNPs was investigated and an MIC of 3.125% was observed on the tested pathogens.

Conclusion: In conclusion, supernatant from LAB cultured using mESM can be used for the production of SNPs with potent antibacterial activity on Gram positive bacteria.