| Summary: | 碩士 === 逢甲大學 === 化學工程學所 === 91 === Gram-positive (Bacillus) and Gram-negative (Pseudomonas) merP genes encoding metal-binding proteins were cloned and expressed in Escherichia coli host. The MerP protein was over-expressed via IPTG induction and the resulting recombinant strains were used to adsorb heavy metals in aqueous solutions of Ni2+, Zn2+ and Cr3+. The initial adsorption rate and adsorption capacity were determined in order to evaluate the feasibility of using the strains as biosorbents for the treatment of wastewater containing heavy metals. The results indicate that the metal adsorption capacity of recombinant strains harboring merP genes were significantly improved for Ni2+ , Zn2+ and Cr3+. Compared to the host cells without merP gene, the adsorption capacity of the strain carrying Gram-positive merP gene (GB) increased 121% and 72% for Zn2+ and Cr3+, respectively. Adsorption capacity of the strain carrying Gram-negative merP gene (GP) also increased 144% and 126% for Zn2+ and Cr3+, respectively. Both recombinant strains also exhibited slight enhancement in capacity for Ni2+ (24% and 5% increase for GB and GP, respectively). The initial adsorption rate of the two recombinant strains also increased in contrast to the original host, indicating that metal-binding affinity or selectivity on recombinant strains was somewhat enhanced. The morphology of cells markedly changed after metal adsorption and exhibited signals of cell lysis. The effect of metal adsorption on cell morphology change was the most significant for Cr3+, followed by Pb2+, Zn2+, Ni2+, Cu2+ and Cd2+. This seems to suggest that metabolite-independent biosorption of heavy metals may occur in the recombinant strains.
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