Journal
CHEMOSPHERE
Volume 176, Issue -, Pages 296-304Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.chemosphere.2017.02.093
Keywords
Klebsiella oxytoca; Biosorption; Proteins; Polysaccharide; Cyclic voltammetry; EXAFS analysis
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Funding
- Ministry of University and Scientific Research (MIUR) [PRIN-2010AXENJ8]
- Slovenian Research Agency programmes [P1-0112]
- [LS-2209]
- [LS-2275]
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A strain of Klebsiella oxytoca DSM 29614 is grown on sodium citrate in the presence of 50 mg l(-1) of Hg as Hg(NO3)(2). During growth, the strain produces an extracellular polymeric substance (EPS), constituted by a mixture of proteins and a specific exopolysaccharide. The protein components, derived from the outer membrane of cells, are co-extracted with the extracellular exopolysaccharide using ethanol. The extracted EPS contains 7.5% of Hg (total amount). This indicates that EPS is an excellent material for the biosorption of Hg2+, through chemical complexation with the EPS components. The binding capacity of these species towards Hg2+ is studied by cyclic voltammetry, and Hg L-3-edge XANES and EXAFS spectroscopy. The results found indicate that Hg2+ is mainly bound to the nitrogen of the imidazole ring or other N-heterocycle compounds. The hydroxyl moities of sugars and/or the carboxyl groups of two glucuronic acids in the polysaccharide can also play an important role in sequestring Hg2+ ions. However, N-heterocyclic groups of proteins bind Hg2+ faster than hydroxyl and carboxyl groups of the polysaccharide. (C) 2017 Elsevier Ltd. All rights reserved.
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