An Optimized Method for the Bioremediation of Se Pollution and the Biosynthesis of Se Nanoparticles with Sodium Selenite-Reducing Bacteria Stenotrophomonas sp. EGS12

Selenium oxide, such as selenite is toxic at high concentrations for animals and humans. Stenotrophomonas sp. EGS12 was screened for the bioremediation of Se pollution by reducing selenite to red selenium nanoparticles. The reduction efficiency of sodium selenite with Stenotrophomonas sp. EGS12 was optimized to obtain the best reaction conditions using a single factor test and response surface analysis. The results showed that the pH and temperature of the reaction mixture significantly ( P <0.05) affected, and the rotating speed also significantly ( P <0.01) affected the reduction efficiency. The methodology of response surface prediction analysis and experimental verification demonstrated that the optimal conditions for synthesizing selenium (Se 0 ) through the reduction of sodium selenite by Stenotrophomonas sp. EGS12 were with a pH = 9, temperature= 35 °C, and rotation speed = 130 rpm, but these effects were relatively independent. The resulting red selenium particles (Se 0 ) were separated and purified. Electron microscope scanning revealed that the size of the red nanoselenium particles ranged from 100–200 nm, and EDX analysis revealed that they contained five elements, C, Se, O, P, and S (32.3%, 61.7%, 4.52%, 1.01%, and 0.47%, respectively). These results may lay the foundation for further development applications of this strain.