Removal of Nickel, Copper, Lead and Cadmium by New Strains of Sphingomonas melonis E8 and Enterobacter hormaechei WW28

Introduction: Bioremediation as eco-friendly technique has high potential to clean-up the toxicity of heavy metals from contaminated soil and water. In this study, the bioremediation potential of E8 and WW28 strains which had high similarity to Sphingomonas melonis and Enterobacter hormaechei, respectively have been evaluated under contaminated mediums with lead (Pb), cadmium (Cd), copper (Cu) and nickel (Ni). Materials and Methods: The growth rate and metal removal percentage of isolated strains were investigated at different ranges of pH 4-8, and temperature (25, 30, 35 and 40˚C). Also, the bioremediation potential of isolated strains was studied under mixture of metals (50 mg/L of each metal). Results: The highest cell mass of strain E8 was observed after 48 hours at 30˚C and pH 5 while strains WW28 showed high growth rate after 72 hours at 25˚C and pH 5. Strains E8 and WW28 preferred to more uptake Ni and Cu than Pb and Cd. In addition, Cd appears to show the highest toxicity towards the isolated bacteria. Strain E8 as multi metals-resistance strain could remove 78%, 62% and 56% of Ni, Cu and Cd, respectively from polluted mediums at pH 6 after 48 hours. Conclusions: Overall results revealed that isolated strains as bio-tools have a high potential to be used in bioremediation process of Ni and multi metals contaminated site