Eco-friendly synthesis of silver nanoparticles using Lactobacillus delbrueckii subsp. bulgaricus isolated from kindrimo (locally fermented milk) in Kano State, Nigeria

Abstract

Silver nanoparticles have gained global popularity because of its application in crucial areas such as medical diagnosis/therapy, solar cell development, water treatment, surface coating and cosmetic production. Bacterial synthesis of silver nanoparticles is regarded as eco-friendly due to minimal waste generated while being energy efficient. This study was aimed at synthesizing silver nanoparticles using Lactobacillus specie isolated from Kindrimo under the influence of sunlight irradiation. Lactobacillus delbrueckii subsp. bulgaricus isolated from Kindrimo was identified using morphological and biochemical techniques and confirmed using 16S rRNA gene sequencing. The eco-friendly protocol for the extracellular synthesis of silver nanoparticles was accomplished by treatment of Lactobacillus delbrueckii subsp. bulgaricus extract with silver nitrate solution in the ratio 1:10 under the influence of sunlight irradiation. Synthesized silver nanoparticles were confirmed and characterized using UV-Visible Spectrophotometry, Dynamic Light Scattering, Transmission Electron Microscopy and Energy Dispersion Spectroscopy. The absorbance spectrum preliminarily confirmed the formation of silver nanoparticles by revealing characteristic broad peak at 415nm. Dynamic Light Scattering measurements further confirmed synthesis by showing average particle size distribution of 147nm. Micrograph of Transmission Electron Microscopy revealed that the synthesized silver nanoparticles were polyhedral and spherical in shape with size ranging 1.4 to 8.9nm. The elemental composition of the resultant colloidal solution was shown to contain silver nanoparticles when subjected to Energy Dispersion Spectroscopy. This study proved that the effect of sunlight irradiation on Lactobacillus mediated synthesis of silver nanoparticles is energy efficient and inexpensive.

Keywords: Silver nanoparticles; UV-Visible Spectrophotometry; Dynamic Light Scattering; Transmission Electron Microscopy; Energy Dispersion Spectroscopy