Microbial Synthesis and Characterization of Silver Nanoparticles using Lactococcus lactis TNM-B1

M.B. Osho, A.O. Precious-Egere, A.O. Awotula, E.A. Ofudje
McPherson University,

Keywords: silver nanoparticle, lactococcus lactis tnm-b1, molecular characterization, fourier transform infra-red spectroscopy and X-ray Diffraction, UV-visible spectroscopy, scanning electron microscopy


The use of bio-nanomaterial as a result of environmental remediation procedure, reliability and eco-friendliness has recorded an outstanding development in nanotechnology science. This work studied the biosynthesis of silver nanoparticles (AgNPs) by Lactococcus lactis TNM-B1 isolated from fermented Tigernut milk. Silver nanoparticles (AgNPs) were characterized by visual observation, UV-Visible Spectroscopy (absorption peak between 400-450 nm for the cell free extract and silver nitrate ratios (1:1; 1:4; 1:9; 3:7) at different concentrations of metal ions (1 mM, 2 mM, 3 mM) and control (without the metal ions)), Fourier Transform Infra-Red Spectroscopy (FTIR), X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Molecular identification of the isolate confirmed it as a strain of L. lactis TNM-B1. Under visual observation, the culture supernatant of L. lactis TNM-B1 was found to have the ability to form silver nanoparticles extracellularly at room temperature within 72 h under 160 rpm as the color changed from colourless to brown an indication of AgNPs production. UV-Visible spectrum showed peak at 400nm which confirmed the presence of nanoparticles of cell free extract and silver nitrate ratio 1:4 of 1mM metal ions concentration. FT-IR spectra were used to identify the presence of the various functional groups present in the biomolecules that could potentially contribute to the reduction of Ag+ ions. The presence of protein as a stabilizing agent which surrounds the nanoparticles was confirmed by FT-IR. The XRD spectra revealed several peaks over the entire spectrum of 2θ values, ranging from 10° to 90°. The structural properties of AgNPs were confirmed using XRD. A comparison of XRD spectra with the standard confirmed that the AgNPs formed in experiments were nanocrystals, as evidenced by the peaks at 2θ values of 32.1°, 46.2°, 57.6°, and 78.0° corresponding to the (111), (200), (220), and (311) planes for silver, respectively. The SEM peaks over the entire spectrum of 2θ values, ranging from 10° to 90° images of the silver nanoparticles sample at different magnification of 5.02 X and 10.0 X. The images showed that most of the silver nanoparticles were predominate as a convex light core, with a compact arrangement and 15.23 mm and 15.28 mm width diameters respectively using advanced software named ‘VEGAJ TESCAN’.