Reduction of Selenite to Red Elemental Selenium by Rhodopseudomonas palustris Strain N

The trace metal selenium is in demand for health supplements to human and animal nutrition. We studied the reduction of selenite (SeO₃ ⁻²) to red elemental selenium by Rhodopseudomonas palustris strain N. This strain was cultured in a medium containing SeO₃ ⁻² and the particles obtained from cultures were analyzed using transmission electron microscopy (TEM), energy dispersive microanalysis (EDX) and X ray diffraction analysis (XRD). Our results showed the strain N could reduce SeO₃ ⁻² to red elemental selenium. The diameters of particles were 80–200 nm. The bacteria exhibited significant tolerance to SeO₃ ⁻² up to 8.0 m mol/L concentration with an EC₅₀ value of 2.4 m mol/L. After 9 d of cultivation, the presence of SeO₃ ²⁻ up to 1.0 m mol/L resulted in 99.9% reduction of selenite, whereas 82.0% (p<0.05), 31.7% (p<0.05) and 2.4% (p<0.05) reduction of SeO₃ ⁻² was observed at 2.0, 4.0 and 8.0 m mol/L SeO₃ ²⁻ concentrations, respectively. This study indicated that red elemental selenium was synthesized by green technology using Rhodopseudomonas palustris strain N. This strain also indicated a high tolerance to SeO₃ ⁻². The finding of this work will contribute to the application of selenium to human health.