Study On Reduction And Detoxification Of Selenite By Photosynthetic Bacteria

In this paper, RhodosPirillaceae complex were isolated to determine the dominant strains by using SEM electron microscope. The morphological characteristics of four strains separated from RhodosPirillaceae complex were observed in the scanning electron microscopy (SEM), Strains initial ratios for Rp.sphaeroides, Rp.palustris, Rp.capsulate and Rm. Vannielii in RhodosPirillaceae complex were percentage of 90.2:6.3:2.4:1.1, respectively.Four strains were respectively cultivated in the optimized culture medium with sodium selenite as inorganic selenium source, Rhodopseudomonas palustris and Rhodopseudomonas capsulata strains with higher tolerance to the inorganic selenium were screened out by measuring the growing bacteria numbers and identifying morphological characteristics. It was fisrt discovery that Rhodopseudomonas palustris tolerated more high concentration of selenium in the experiment。Effect of carbon source in fermentation medium, inoculum and PH value on the bacterial growth were investigated based on optimized fermentation medium with sodium selenite. Rhodopseudomonas palustri and Rhodopseudomonas capsulata growth number were greater than 2.2×109per milliliter when the cultivation conditions control PH value at 6-7, inoculum at 20% and yeast extract as carbon source Rhodopseudomonas palustris and Rhodopseudomonas capsulata adapted to grow at the [SeO32-] concentrations in the range of 25-50μg/mL during selenium gradient culture experiments.The two photosynthetic bacteria growth would be inhibited when [SeO32-] concentration come abover 100μg/mL with [SeO32-] toxicological effect.The selenite reduced conditions based on using the two photosynthetic bacteria were optimized by means of single factor experiment and L9 (33) orthogonal test. The reduction rates of selenite by Rhodopseudomonas palustris and Rhodopseudomonas capsulata were at 98.24% and 98.97% respectively in the optimal condition of 15% inoculums and 100μg/mL of [SeO32-] concentration for 5d incubation.Reduction and detoxification of selenite into elemental selenium were investigated in. The results suggested that Rhodopseudomonas palustris had the ability to reduce selenite into red non-toxic elemental selenium identified by transmission electron microscopy (TEM). The molecular weight of the selenite reductase separated and purified from Rhodopseudomonas palustris was determined around 182 kDa by SDS-PAGE Electrophoresis.