Efficiency of Escherichia coli Jm109 and genetical engineering strains (E. coli MT2, E. coli MT3) in cadmium removal from aqueous solutions

Abstract

Metallothioneins (MTs) are proteins with high metal binding affinity that exist in many organisms. Recently, this feature of MTs has been used in many areas, including environmental studies. In this study, the human MT2, and MT3 genes were cloned into Escherichia coli Jm109 to remove cadmium (Cd) from aqueous solutions. Minimum inhibition concentrations (MIC) of Cd for E. coli Jm109, E. coli MT2, and E. coli MT3 were determined as 154, 212, and 250 mg L −1 , respectively. 0.5, 5, and 25 mg L −1 Cd were applied to the strains. The maximum Cd removal was at the concentration of 0.5 mg L −1 . The optimal conditions for temperature, pH, and contact time were 37 °C, 7, and 24 h, respectively. E. coli MT3 was the most effective strain in Cd bioremoval. Scanning electron microscope (SEM) images showed that the morphological structures of the Cd treated cells were disrupted. The Energy dispersive spectroscopy (EDS) peaks of the Cd treated cells clearly showed Cd absorption into the cells. Scanning transmission electron microscope (STEM) images showed that there were clusters reflecting the accumulation of Cd in the MT3 cells. The appearance of attenuated total reflectance fourier transform infrared spectroscopy (ATR-FTIR) spectrum peaks of hydroxyl, carboxyl, amine, and sulfoxide groups in MT3 cells exposed to Cd confirmed that these groups bind Cd. As a result, it can be said that the MT3 gene can be used as an effective tool in Cd removal from waters. • The Cd removal capacities of genetically modified Escherichia coli were high. • E. coli MT3 was more effective in Cd removal than E. coli Jm109 and E. coli MT2. • SEM and STEM images showed that E. coli MT3 absorbs more Cd than other strains. • ATR-FTIR spectrum peaks confirmed that MT3 cells bind Cd. • MT3 can be used as an effective tool in Cd removal from water.