Using Recombinant E. coli Displaying Surface Heavy Metal Binding Proteins for Removal of Pb2+ from Contaminated Water

Water pollution remains a serious problem with economic and public health concerns worldwide. Lead (Pb2+) is one of the dangerous metals related to chronic diseases and is responsible for many deaths around the world. Despite the advances in technologies for removal of heavy metals e.g., Pb2+ from water, all current techniques have shown some limitations that obstructed their application. Bearing in mind that there is a need to develop a novel technique for removal of heavy metals from water, we developed a quick, specific and efficient method for removal of Pb2+ from water using dead cells of recombinant Escherichia coli. Recombinant E. coli were engineered to display metallothionein (SmtB) and lead binding protein (PbrR) onto outer membrane. DNA fragments encoding these proteins were fused to DNA fragment encoding β- domain of antigen 43 (Ag43) for translocation of both heavy metal binding proteins. The resultant recombinant E. coli exhibited a capability to adsorb Pb2+ successfully from water samples containing 100 mg/L of Pb2+, and concentrations of Pb2+ reached to undetectable level after 18 hours. Heat-inactivated E. coli displaying PbrR and SmtB on outer membrane showed comparable removal efficiencies to live E. coli cells. These observations suggest that our method can be used as a promising, specific and efficient approach for removal of Pb2+ from contaminated water.