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Using recombinant E. coli displaying surface heavy metal binding proteins for removal of Pb2+ from contaminated water

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Title: Using recombinant E. coli displaying surface heavy metal binding proteins for removal of Pb2+ from contaminated water
Other Titles: 汚染水からの鉛除去のための表在性重金属結合タンパク質提示組換え大腸菌の利用
Authors: Shehata, Mohamed Browse this author
Issue Date: 25-Sep-2018
Abstract: Water pollution remains a serious problem with economic and public health concerns worldwide. Lead (Pb)is one of the dangerous metals related to chronic diseases and is responsible for hundreds of thousands of deaths around the world. Exposure to Pb2+ is cumulative over time. High concentrations of Pb2+ in the body can cause death or permanent damage to the central nervous system, the brain, and kidney. This damage commonly results in behavior and learning problems (such as hyperactivity), memory and concentration problems, high blood pressure, hearing problems, headaches, retardation of growth, reproductive problems in men and women, digestive problems, muscle and joint pain. 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. Taking advantages of usage of surface-displaying proteins by E. coli for improving the removal efficiencies of Pb2+, we engineered recombinant E. coli 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 metals binding protein 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. The present study revealed that E. coli cells have the characteristics to remove Pb2+ from acidic solution, which is a difficult issue because of the high solubility of Pb2+ compounds in acidic condition. Unlike the most common methods for removal of Pb2+ from wastewater (chemical precipitation in alkaline solution), this method could be considered for removal of Pb2+ at acidic solution. It is believed that removal of heavy metals by bacteria depending on their specific binding activity to metal ions has a major concern toward releasing of recombinant organisms into the environment. However, it is noteworthy to mention that heat-treatment (at 60°C for 60 min) is enough to remove viability of recombinant E. coli strains without losing its activity to bind Pb2+, which is an important finding for the possibility of application of this system. These observations suggest that this method can be used as a promising, specific and efficient tool for removal of Pb2+ from contaminated water.
Conffering University: 北海道大学
Degree Report Number: 甲第13311号
Degree Level: 博士
Degree Discipline: 環境科学
Examination Committee Members: (主査) 准教授 山崎 健一, 教授 森川 正章, 教授 鈴木 仁
Degree Affiliation: 環境科学院(生物圏科学専攻)
Type: theses (doctoral)
Appears in Collections:学位論文 (Theses) > 博士 (環境科学)
課程博士 (Doctorate by way of Advanced Course) > 環境科学院(Graduate School of Environmental Science)


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