Hg2+ Removal by Genetically Engineered Escherichia coli in a Hollow Fiber Bioreactor

Abstract

Escherichia coli cells engineered to express an Hg2+ transport system and metallothionein accumulated Hg2+ effectively over a concentration range of 0.2-4 mg/L in batch systems. Bioaccumulation was selective against other metal ions and resistant to changes in ambient conditions such as pH, ionic strength, and the presence of common metal chelators or complexing agents (Chen, S.-L.; Wilson, D. B. Appl. Environ. Microbiol. 1997, 63, 2442-2445; Biodegradation 1997, 8, 97-103). Here we report the characterization of the bioaccumulation system based on its kinetics and an isotherm. Bioaccumulation was rapid and followed Michaelis-Menten kinetics. A hollow fiber bioreactor was constructed to retain the genetically engineered cells. The bioreactor was capable of removing and recovering Hg2+ effectively at low concentrations, reducing a 2 mg/L solution to about 5 microgram/L. A mathematical equation that quantitatively described Hg2+ removal by the bioreactor provides a basis for the optimization and extrapolation of the bioreactor. The genetically engineered E. colicells and the bioreactor system have excellent properties for bioremediation of Hg2+-contaminated environments.

Mercury Pollution and Bioremediation—A Case Study on Biosorption by a Mercury-Resistant Marine Bacterium

“…Mercury is a heavy metal with extreme toxicity, and, owing to its ability to biomagnify and its high residence time in the environment, it causes havoc for other living organisms as well as the ecosystem. Technologies for treating mercury-polluted environments have been a major concern over the last couple of decades (Williams and Silver, 1984;Nakamura et al, 1990;Brunke et al, 1993;Canstein et al, 1999;Canstein, 2000;Chang et al, 1997, Chen et al, 1998Essa et al, 2002;Wagner-Döbler, 2003;Deckwer et al, 2004). Common methods to remove Hg 21 from contaminated water are mostly based on sorption to materials such as ion exchange resins (Osteen and Bibler, 1991;Ritter and Bibler, 1992).…”

“…Reduction of Hg by MRB as the best such mechanism for its removal from chloralkali waste has been demonstrated (Canstein et al, 1999;Wagner-Döbler, 2003). Biosorption, another biological method involving adsorption of metals into the algal or bacterial biomass (either dead or alive), has been inexpensive and also promising (Chang and Hong, 1994;Mulligan et al, 2001), but is applicable only to low concentrations of metals in water (Chen et al, 1998). Saouter et al (1994Saouter et al ( , 1995 reported their preliminary investigation on using Hg 21 -reducing strains to decontaminate a polluted pond in Tennessee.…”

Effect of ambient conditions on simultaneous growth and bioaccumulation of mercuric ion by genetically engineered E. coli JM109

“…The dry weight of cells was determined from OD 600 using the value of 0.35 g dry weight per liter of OD 600 1.0 [13]. The Hg 2+ concentration was determined by intelligent cold vapor atom fluorescence mercuric ion measurement.…”

Continuous treatment process of mercury removal from aqueous solution by growing recombinant E. coli cells and modeling study

“…A hollow-fiber bioreactor was used in the system to retain the cells and more than 99% of mercuric ions in the wastewater were effectively accumulated. Chen and Kim realized a continuous treatment on Hg 2+ removal by recombinant E. coli in a hollow-fiber bioreactor [13]. Other researchers also set up some continuous processes to accumulate heavy metal ions with biomass [5,14,15].…”