Application of Response Surface Methodology in optimization of Selenate bioreduction to selenium nanoparticles by Bacillus sp. Strain TR-6

Biomineralization of selenium by bacteria not only has the potential to remove toxic selenium oxyanions from the environment, but can also produce nano- scale elemental selenium. In this work, the response surface method (RSM) based on the Box- Behnken design was used for evaluation and optimization of the different process parameters effect on the bioreduction process of selenate. The proposed second order model with a correlation coefficient R2 = 0.96 appropriately predicted the process behavior and determined the 41.25 percent reduction of selenate by Bacillus sp. Strain TR-6 at 5.24 percent initial bacterial inoculation, process time of 24 h and 3.8 mM concentration of sodium selenate as the optimum condition. Scanning electron microscope (SEM) with the Energy Dispersive X-ray spectroscopy (EDX) confirmed the ability of the selected bacteria to produce selenium nanospheres. Finally, Bacillus sp. Strain TR-6 is determined as a valuable candidate for nano- technologies and selenium biomineralization processes.