Abstract

Introduction: Soil bacteria that synthesize varying metallic NPs are underreported, even though there is a promising mechanism in the bio-reduction of gold salts and the synthesis of gold nanoparticles by different bacterial species.

Objective: This study aimed to explore the ancillary potential of some soil microbes obtained from a metal fabricating workshop for gold nanoparticles (AuNPs) synthesis.

Methods: To evaluate the usefulness of these soil microbes, 1 mM chloroauric acid (HAuCl4.4H2O) was bio-reduced using the wet biomass of these bacterial cells and characterized with UV-Vis spectrophotometer, Fourier Transform Infra-red (FTIR), Scanning Electron Microscope (SEM), Energy Dispersive X-ray (EDX), and X-ray Diffractometer (XRD).

Results: Findings from this study showed that the studied bacterial isolates synthesized AuNPs with absorbance peaks within the range of 500 and 600 nm. The FTIR analysis showed the involvement of O-H, N-H, and C=O stretch of alcohol, amine, and amide groups, respectively. The SEM images analyzed with Image J reported a mean area size between 17-184 nm. The EDX showed Klebsiella africana (C11), and Bacillus subtilis (A12) had the lowest (7.32%) and highest (51.26%) weight percentages of AuNPs, respectively.

Conclusion: Gold nanoparticles have been found most appropriate for several novel applications, and this work has provided further understanding of the capacity of naturally occurring bacteria to be non-selective in the bio-reduction of gold salts, hence expanding their potential uses.

Keywords: Bio-reduction activity, microbial synthesis, gold nanoparticles, metal-reducing bacteria, klebsiella species, bacillus species.