Chen S, Wilson D B
Institute for Comparative and Environmental Toxicology, Cornell University, Ithaca, NY 14853, USA.
Biodegradation. 1997;8(2):97-103. doi: 10.1023/a:1008233704719.
Ion exchange or biosorptive processes for metal removal generally lack specificity in metal binding and are sensitive to ambient conditions, e.g. pH, ionic strength and the presence of metal chelators. In this study, cells of a genetically engineered Escherichia coli strain, JM109, which expresses metallothionein and a Hg2+ transport system after induction were evaluated for their selectivity for Hg2+ accumulation in the presence of sodium, magnesium, or cadmium ions and their sensitivity to pH or the presence of metal chelators during Hg2+ bioaccumulation. The genetically engineered E. coli cells in suspension accumulated Hg2+ effectively at low concentrations (0-20 microM) over a broad range of pH (3 to 11). The presence of 400 mM sodium chloride, 200 mM magnesium chloride, or 100 microM cadmium ions did not have a significant effect on the bioaccumulation of 5 microM Hg2+, indicating that this process is not sensitive to high ionic strength and is highly selective against sodium, magnesium, or cadmium ions. Metal chelators usually interfere with ion exchange or biosorptive processes. However, two common metal chelators, EDTA and citrate, had no significant effect on Hg2+ bioaccumulation by the genetically engineered strain. These results suggest that this E. coli strain could be used for selective removal of Hg2+ from waste water or from contaminated solutions which are resistant to common treatments. A second potential application would be to remove Hg2+ from Hg(2+)-contaminated soil, sediment, or particulates by washing them with a Hg2+ chelator and regenerating the chelator by passing the solution through a reactor containing the strain.
用于金属去除的离子交换或生物吸附过程通常在金属结合方面缺乏特异性，并且对环境条件敏感，例如pH值、离子强度和金属螯合剂的存在。在本研究中，对一种基因工程大肠杆菌菌株JM109的细胞进行了评估，该菌株在诱导后表达金属硫蛋白和Hg2+转运系统，研究其在存在钠、镁或镉离子的情况下对Hg2+积累的选择性，以及在Hg2+生物积累过程中对pH值或金属螯合剂存在的敏感性。悬浮状态下的基因工程大肠杆菌细胞在较宽的pH范围（3至11）内，能在低浓度（0 - 20微摩尔）下有效地积累Hg2+。400毫摩尔氯化钠、200毫摩尔氯化镁或100微摩尔镉离子的存在对5微摩尔Hg2+的生物积累没有显著影响，这表明该过程对高离子强度不敏感，并且对钠、镁或镉离子具有高度选择性。金属螯合剂通常会干扰离子交换或生物吸附过程。然而，两种常见的金属螯合剂，乙二胺四乙酸（EDTA）和柠檬酸盐，对该基因工程菌株的Hg2+生物积累没有显著影响。这些结果表明，这种大肠杆菌菌株可用于从废水或对常规处理有抗性的污染溶液中选择性去除Hg2+。第二个潜在应用是通过用Hg2+螯合剂洗涤Hg(2+)污染的土壤、沉积物或颗粒物，并使溶液通过含有该菌株的反应器来再生螯合剂，从而去除其中的Hg2+。
