Intensified biosynthesis of silver nanoparticles using a native extremophilic Ureibacillus thermosphaericus strain

The microflora of Ramsar geothermal hot springs located in Mazandaran province, Iran was screened for native thermophilic bacteria that are capable of biosynthesis of silver nanoparticles. One isolate identified as Ureibacillus thermosphaericus showed high potential for silver nanoparticle biosynthesis with extracellular mechanism and selected for the biosynthesis optimization. Biosynthesis reactions were conducted using the culture supernatant at different temperatures (60-80 degrees C) and silver ion concentrations (0.001-0.1 M). The results obtained showed that pure spherical nanoparticles in the range of 10-100 nm were produced, and the maximum nanoparticle production was achieved using 0.01 M Ag-NO3 at 80 degrees C. In conclusion, the findings of this study confirmed the great biocatalyzing potential of the extremophilic U. thermosphaericus supernatant for intensified biosynthesis of silver nanoparticle at elevated temperatures and high silver ion concentrations. (C) 2011 Elsevier B.V. All rights reserved.