title: An extracellular polymeric substance quickly chelates mercury(II) with N-heterocyclic groups.
abstract: A strain of Klebsiella oxytoca DSM 29614 is grown on sodium citrate in the presence of 50 mg l-1of 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 L3-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.
authors.affiliation: Dipartimento di Scienze Molecolari e Nanosistemi, University Cà Foscari Venezia, Via Torino 155, 30172, Mestre Venezia, Italy. Electronic address: baldi@unive.it.
authors.forename: Franco
authors.initials: F
authors.lastname: Baldi
authors.affiliation: Dipartimento di Scienze Molecolari e Nanosistemi, University Cà Foscari Venezia, Via Torino 155, 30172, Mestre Venezia, Italy.
authors.forename: Michele
authors.initials: M
authors.lastname: Gallo
authors.affiliation: Dipartimento di Scienze Molecolari e Nanosistemi, University Cà Foscari Venezia, Via Torino 155, 30172, Mestre Venezia, Italy.
authors.forename: Salvatore
authors.initials: S
authors.lastname: Daniele
authors.affiliation: Dipartimento di Scienze Ambientali, Informatica e Statistica, University Cà Foscari Venezia, Via Torino 155, 30172, Mestre Venezia, Italy; Institute for the Dynamics of Environmental Processes, IDPA/CNR, Via Torino, 155, 30172, Mestre Venezia, Venice, Italy.
authors.forename: Dario
authors.initials: D
authors.lastname: Battistel
authors.affiliation: Dipartimento Scienze della Vita, Siena University, Via Mattioli 4, 53100, Siena, Italy.
authors.forename: Claudia
authors.initials: C
authors.lastname: Faleri
authors.affiliation: Jozef Stefan Institute, Jamova 39, Ljubljana, Slovenia; Faculty of Mathematics & Physics, University of Ljubljana, Slovenia.
authors.forename: Alojz
authors.initials: A
authors.lastname: Kodre
authors.affiliation: Jozef Stefan Institute, Jamova 39, Ljubljana, Slovenia; University of Nova Gorica, Vipavska 13, Nova Gorica, Slovenia.
authors.forename: Iztok
authors.initials: I
authors.lastname: Arčon
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry; D002614:Chelating Agents / Q000737:chemistry* / Q000378:metabolism; D006571:Heterocyclic Compounds / Q000737:chemistry*; D041121:Klebsiella oxytoca / Q000378:metabolism* / Q000648:ultrastructure; D017669:Mercury Compounds / Q000032:analysis* / Q000378:metabolism; D008962:Models, Theoretical; D009566:Nitrates / Q000032:analysis* / Q000378:metabolism; D011135:Polysaccharides, Bacterial / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D002614:Chelating Agents; D006571:Heterocyclic Compounds; D017669:Mercury Compounds; D009566:Nitrates; D011135:Polysaccharides, Bacterial; D014874:Water Pollutants, Chemical; C029948:mercury nitrate
keywords: Biosorption; Cyclic voltammetry; EXAFS analysis; Klebsiella oxytoca; Polysaccharide; Proteins