Green synthesis of silver nanoparticles by Bacillus methylotrophicus, and their antimicrobial activity

Abstract

The synthesis of silver nanoparticles (AgNPs) by microorganisms is an area attracting growing interest in nanobiotechnology, due to the applications of these nanoparticles in various products including cosmetics and biosensors, and in the biomedical, clinical, and bioimaging fields as well. Various microorganisms have been found to be able to synthesize AgNPs when silver salts are supplied in the reaction system. The main objectives of this study were to evaluate the efficiency of synthesis of AgNPs by the strain Bacillus methylotrophicus DC3, isolated from the soil of Korean ginseng, a traditionally known oriental medicinal plant in Korea. The AgNPs showed maximum absorbance at 416 nm, when assayed by ultraviolet-visible spectroscopy (UV-vis). The field emission transmission electron micrograph (FE-TEM) results showed that the particles were spherical and 10–30 nm in size. In addition, the product was also characterized by energy dispersive X-ray spectroscopy (EDX), which displayed a 3 keV peak corresponding to the silver nanocrystal. Elemental mapping results also confirmed the presence of silver elements in the electron micrograph region. Furthermore, the AgNPs demonstrated antimicrobial activity against various pathogenic microorganisms such as Candida albicans, Salmonella enterica, Escherichia coli, and Vibrio parahaemolyticus, with enhanced antimicrobial activity being exhibited against C. albicans. Therefore, the current study describes the simple, efficient, and green method of synthesis of AgNPs by B. methylotrophicus DC3.

Keywords::

• antimicrobial activity
• Bacillus methylotrophicus
• green synthesis
• silver nanoparticles

Acknowledgments

This research was supported by the Korea Institute of Planning & Evaluation for Technology in Food, Agriculture, Forestry & Fisheries (KIPET NO: 313038-03-2-SB010), and also was supported by Business for Cooperative R & D between Industry, Academy, and Research Institute funded KSMB (Grants No.C0214183).

Declaration of interest

The authors report no declarations of interest. The authors alone are responsible for the content and writing of the paper.