The Performance Of Cr(?)Reduction By Lysinibacillus Sp.ReCr-13 And Its Response Of Cr(?)Induced Oxidative Stress

With the development of industries,a large amount of Cr(?)containing wastewater has been discharged,which leads to ecological damage.The toxicity of Cr(?)could cause carcinogenic,teratogenic,and mutagenic effects on human.Cr(?)bioremediation has attracted much attention due to its simple operation,less expensive and environmental friendly.In this paper,a new strain with high Cr(?)reduction potential was isolated from river sludge.Some experiments were conducted to optimize various parameters in Cr(?)reudction process.Cr(?)bioreudction machanism was also carried out.The effect of Cr(?)concentration on Cr(?)reduction efficiency under higher Cr(?)concentration were investigated carefully.The results were listed as follows:(1)A Cr(?)reducing strain was isolated by plate separation method and identified as Lysinibacillus sp.ReCr-13.Through the investigation of single factor experiments,it was found that the optimum Cr(?)reduction and bacterial growth were obtained at pH 8.0 and pH 9.0,respectively.The maximum bacterial growth and Cr(?)reduction were obtained at 5.0 g/L NaCl.The bacterial growth and Cr(?)reduction decreased with the increase of initial Cr(?)concentration.The bacterial growth and Cr(?)reduction could be inhibited by Ni2+and Zn2+,while promoted by Mn2+.The bacterial growth could be promoted by glucose while Cr(?)reduction promoted by sodium citrate significantly.Strain ReCr-13 was used to treat Cr(?)containing wastewater,and the bacterial growth and Cr(?)reduction decreased with the increase of initial Cr(?)concentration.(2)Cell free extract was the main component for Cr(?)reduction and mediated by intracellular enzymes.None of chromium was on bacteria and most of Cr(?)were reduced to form soluble Cr(?)complexes in supernatant.(3)The content of intracellular superoxide anion(O2-),hydrogen peroxide(H2O2),and malondialdehyde(MDA)in Lysinibacillus sp.ReCr-13 increased with the increase of initial Cr(?)concentration.However,the content of intracellular O2-,H2O2 and MDA could be effectively reduced by exogenous Mn2+,and the activity of superoxide dismutase(SOD)and catalase(CAT),as well as the total antioxidant activity(TAA)were improved,It was concluded that oxidative stress induced by Cr(?)is one of primary reasons for the decrease of Cr(?)reduction efficiency by Lysinibacillus sp.ReCr-13 under high initial Cr(?)concentration.