| Summary: | 碩士 === 逢甲大學 === 化學工程學所 === 90 === Abstract
Gram-positive (Bacillus) and Gram-negative (Pseudomonas) merP gene encoding metal-binding proteins strain was cloned and expressed in Escherichia coli host. The MerP protein was over-expressed via IPTG induction and the resulting recombinant strains were subject to adsorb heavy metals in single- and multi-metal systems in order to evaluate the feasibility of using these strains as the biosorbent for the treatment of heavy-metal wastewater. Results indicate that the metal adsorption capacity of recombinant strain harboring Gram-positive merP was significantly improved with a 142% increase for Cu2+ and a 47% increase for Cd2+ over the metal-binding capacity of host cells without merP gene. The adsorption capacity of the strain carrying Gram-negative merP also increased 85% and 55% for Cu2+ and Cd2+, respectively. In contrast, the two recombinant strain did not show visible enhancement on biosorption of Pb. Results of multi-metal biosorption show that the preference of metal biosorption by the two recombinant strains decreased in the order of Cu > Pb > Cd. On the other hand, the amino acid sequence fragments associated with metal-binding site from Gram-positive (GMDCCPP) and Gram-negative (GMTCAACP) MerP protein were chemically synthesized and covalently immobilized on Celite carrier to perform metal-binding experiments. The results show that the Cu-binding capacity was 0.239 and 0.142 mol/mol-peptide for Gram-positive and Gram-negative peptides, respectively. The two peptides showed similar capacity of 0.036 mol/mol-peptide for Cd. The trend of metal biosorption was similar for whole cells and the oligo peptides, suggesting that the MerP protein expressed in the recombinant strains may account for the improvement of metal biosorption. As the strain containing gram-positive merP gene and the peptide from gram-positive MerP protein exhibited better metal adsorption capacity, it seems that the strain harboring Gram-positive merP has a better potential to be used in practical wastewater treatment.
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