Adsorption Of Hg²⁺/Cr⁶⁺ Byheavy Metal Binding Proteins Heterologously Expressed In Escherichia Coli

At present,due to the universality and harmfulness ofheavy metal pollution,it is increasingly urgent to construct target strains and adsorb heavy metal ions in the environment.In response to this goal,our research constructed a heavy metal repair target strain which aims to realize the bioremediation of heavy metal pollution in water.Our research fused the N-terminal sequence of ice nucleoprotein chosen as an anchor carrier with 10 heavy metal binding proteins through 5 connection methods,producing 50 target strains of heavy metal binding protein surface display.Using metal regulatory proteins Mer R,Mer R_opt,Chr B,Chr Bopt with specific bidirectional promoters,16 target strains were constructed based on the location of genetic elements including regulatory protein and its promoter.The target strains M’-002(Hg²⁺),B’-002(Cr⁶⁺),M’-006(Hg²⁺)and B-008(Cr⁶⁺)were obtained by pre-screening.Based on the constructed heavy metal bioremediation target strain,the influence of the three factors of inducer concentration,induction temperature,and induction time on the ability of the target strain to adsorb Cr⁶⁺/Hg²⁺was investigated.The experiment found that the three factors that affect the adsorption capacity of the target strains in descending order are the induction temperature,the concentration of the inducer,and the induction time.When the induction temperature is 26℃,the concentration of the inducer is 1.0 m M,and the induction time is 22h,the Hg²⁺adsorption capacity of the target strains M’-002 and M’-006 reaches the maximum557.76μmol/g CDW and 488.34μmol/g CDW;target The Cr⁶⁺adsorption capacity of strain B’-002 reached the maximum 28.09μmol/g CDW.When the induction temperature is 24℃,the inducer concentration is 1.0 m M,and the induction time is22h,the Cr⁶⁺adsorption capacity of the target strain B-008 reaches the maximum37.69μmol/g CDW.Our research also explored the influence of the concentration of heavy metal ions on the absorption capacity of the target strains,and the adsorption of each metal by these strains in the presence of multiple heavy metal ions.At 300μM of Hg²⁺,target strains both M’-002 and M’-006 reach the maximum adsorption capacity with 658.66μmol/g CDW and 602.34μmol/g CDW respectively.The adsorption of Cr⁶⁺by target strains B’-002 and B-008 also ascends to the peak,respectively 28.48μmol/g CDW and 46.75μmol/g CDW,when the Cr⁶⁺concentration is 300μM.Finally,by co-culturing the target strains M’-002 and B-008,a mixed bacteria system was constructed to inspect its adsorption performance.When the concentration of heavy metal ion comes to 500μM,mixed bacteria adsorb the maximum Hg²⁺and Cr⁶⁺,respectively 419.02μmol/g CDW,50.61μmol/g CDW.Compared with the single target strain,mixed bacteria can adsorb more Cr⁶⁺but less Hg²⁺.In general,the target strains designed and constructed in this study have a high adsorption capacity for heavy metals.For its highly application value,our research provides a good basis for the bioremediation of heavy metal polluted environments.