Extracellular synthesis of silver nanoparticles by the Bacillus strain CS 11 isolated from industrialized area

Roshmi Thomas,Rintu T. Varghese,Jyothis Mathew,Vidhya Lakshmi Das,E. K. Radhakrishnan,E. V. Soniya

doi:10.1007/s13205-013-0130-8

Abstract

Biological synthesis of silver nanoparticles using microorganisms has received profound interest because of their potential to synthesize nanoparticles of various size, shape and morphology. In the current study, synthesis of silver nanoparticles by a bacterial strain (CS 11) isolated from heavy metal contaminated soil is reported. Molecular identification of the isolate showed it as a strain of Bacillus sp. On treating the bacteria with 1 mM AgNO3, it was found to have the ability to form silver nanoparticles extracellularly at room temperature within 24 h. This was confirmed by the visual observation and UV–Vis absorption at 450 nm. Further characterization of nanoparticles by transmission electron microscopy confirmed the size of silver nanoparticles in 42–92 nm range. Therefore, the current study is a demonstration of an efficient synthesis of stable silver nanoparticle by a Bacillus strain.

Highlights

Nanotechnology involving synthesis and applications of nanomaterials is a rapidly growing field with significant applications in various areas (Duran et al 2005)
The sequence data were subjected to BLAST analysis and the result showed its maximum identity of 99 % to various Bacillus sp. mainly Bacillus cereus (Fig. 1)
A bacterial strain isolated from heavy metal contaminated soil samples was found to have resistance to silver nitrate

Summary

Introduction

Nanotechnology involving synthesis and applications of nanomaterials is a rapidly growing field with significant applications in various areas (Duran et al 2005). Microbial synthesis of nanoparticles is eco-friendly and has significant advantages over other processes since it takes place at relatively ambient temperature and pressure (Gade et al 2008; Mukherjee et al 2008; Wei et al 2012). Microbial synthesis of metal nanoparticles can take place either intracellularly or extracellularly (Ahmad et al 2003, 2007; Jain et al 2011; Kalishwaralal et al 2010; Pugazhenthiran et al 2009; Saifuddin et al 2009). At the same time extracellular biosynthesis is cheap and it requires simpler downstream processing. This favours large-scale production of silver nanoparticles to explore its potential applications. Many studies were focussed on extracellular methods for the synthesis of metal nanoparticles (Duran et al 2005). When the culture supernatant of Bacillus megaterium was treated with aqueous solutions of Ag? ions, within few minutes it formed silver nanoparticles (AgNPs) extracellularly (Saravanan et al 2011)

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Conclusion