| Abstract | The bioconversion of the inorganic Se(IV) to elemental selenium form by yoghurt culture was investigated. The whey-yeast extract media were mixed with 1, 2, 5, 10 and 20 ppm of Se(IV) and incubated with yoghurt culture at 40 oC for 24 h. Up to 5 ppm of Se, the bacterial growth rate closely resembled that of the control. However, cells grown in the presence of 10 and 20 ppm of Se(IV) showed longer lag phase and low growth rates compared to the other treatments. A red color of the element Se was accumulated in the bacterial cell cultivated with more than 5 ppm of Se after 24 h of incubation. A dose independent bioconversion rate of selenium to organic and elemental form was observed in the media supernatant. The inorganic Se was completely bioconverted in the cultured media at the level of 1 ppm after 4 h of incubation. But in higher concentration elemental selenium nanospeheres were formed inside the bacteria as the result of detoxification mechanism. According to the electronmicroscopy pictures, the size of spheres is in the 100-500 nm range and controlled by the species of bacteria. Applying only one species of bacteria a very homogenious particle size distribution of the produced elemental selenium can be achieved. |