Biosorption of lead (II) and cadmium (II) using Escherichia coli genetically engineered with mice metallothionein I.

Contamination caused by heavy metals in wastewater has a high potential of risk because they easily penetrate in to the trofic chain accumulating as organometallic compounds. In this work, the expression of mice metallothionein in E. coli (pMt-Thio) was examined as a strategy to enhance metal biosorption efficiency of bacterial biosorbents for Pb(II) and Cd(II) ions. The results showed that pMt-Thio led to significant increase in overall biosorption capacity, especially for biosorption of Pb. Isotherms and kinetic of biosorption were evaluated in this designed system. The influence of metal concentration in solution is discussed in terms of Langmuir and Freundlich isotherm and constants. The Langmuir model was found to correlate better with the experiment data. The biomass showed maximum capacities according to Langmuir adsorption model of 28.14 mgPb/gpMt-Thio and 24.27 mgCd/gpMt-Thio. The study proved that pMt-Thio is a suitable material for the removal of the heavy metal ions studied from aqueous solutions, achieving removal efficiencies higher than 90% for Pb(II) and higher than 40% for Cd(II), and could be considered as a potential material for treating effluent polluted with Cd(II) and Pb(II) ions.