Engineering bacterial biopolymers for the biosorption of heavy metals; new products and novel formulations |
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Authors: | D L Gutnick H Bach |
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Institution: | (1) Department of Molecular Microbiology and Biotechnology, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Tel-Aviv 69978, Israel e-mail: davidg@post.tau.ac.il Tel.: +972-3-6409834 Fax: +972-3-6425786/6409407, IL |
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Abstract: | Bioremediation of heavy metal pollution remains a major challenge in environmental biotechnology. One of the approaches considered
for application involves biosorption either to biomass or to isolated biopolymers. Many bacterial polysaccharides have been
shown to bind heavy metals with varying degrees of specificity and affinity. While various approaches have been adopted to
generate polysaccharide variants altered in both structure and activity, metal biosorption has not been examined. Polymer
engineering has included structural modification through the introduction of heterologous genes of the biosynthetic pathway
into specific mutants, leading either to alterations in polysaccharide backbone or side chains, or to sugar modification.
In addition, novel formulations can be designed which enlarge the family of available bacterial biopolymers for metal-binding
and subsequent recovery. An example discussed here is the use of amphipathic bioemulsifiers such as emulsan, produced by the
oil-degrading Acinetobacter lwoffii RAG-1, that forms stable, concentrated (70%), oil-in-water emulsions (emulsanosols). In this system metal ions bind primarily
at the oil/water interface, enabling their recovery and concentration from relatively dilute solutions. In addition to the
genetic modifications described above, a new approach to the generation of amphipathic bioemulsifying formulations is based
on the interaction of native or recombinant esterase and its derivatives with emulsan and other water-soluble biopolymers.
Cation-binding emulsions are generated from a variety of hydrophobic substrates. The features of these and other systems will
be discussed, together with a brief consideration of possible applications.
Received: 2 February 2000 / Received revision: 2 June 2000 / Accepted: 3 June 2000 |
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