, Volume 25, Issue 5, pp 875–881 | Cite as

XAS analysis of a nanostructured iron polysaccharide produced anaerobically by a strain of Klebsiella oxytoca

  • Iztok ArčonEmail author
  • Oreste Piccolo
  • Stefano Paganelli
  • Franco Baldi


A strain of Klebsiella oxytoca, isolated from acid pyrite-mine drainage, characteristically produces a ferric hydrogel, consisting of branched heptasaccharide repeating units exopolysaccharide (EPS), with metal content of 36 wt%. The high content of iron in the EPS matrix cannot be explained by a simple ferric ion bond to the sugar skeleton. The bio-generated Fe–EPS is investigated by X-ray absorption spectroscopy. Fe K-edge XANES analysis shows that iron is mostly in trivalent form, with a non-negligible amount of Fe2+ in the structure. The Fe EXAFS results indicate that iron in the sample is in a mineralized form, prevalently in the form of nano-sized particles of iron oxides/hydroxides, most probably a mixture of different nano-crystalline forms. TEM shows that these nanoparticles are located in the interior of the EPS matrix, as in ferritin. The strain produces Fe–EPS to modulate Fe-ions uptake from the cytoplasm to avoid iron toxicity under anaerobic conditions. This microbial material is potentially applicable as iron regulator.


Anaerobic growth Citrate fermentation Fe–EPS Fe K-edge XANES EXAFS 



This research was supported by the Slovenian Research Agency (P1-0112). Access to synchrotron radiation facilities of ELETTRA (beamline XAFS) is acknowledged. Giuliana Aquilanti and Luca Olivi of ELETTRA are acknowledged for expert advice on beamline operation.


  1. Arčon I, Mozetič M, Kodre A (2005) XAS study of oxygen-plasma treated micronised iron-oxide pigments. Vacuum 80:178–183CrossRefGoogle Scholar
  2. Arčon I, Kolar J, Kodre A, Hanžel D, Strlič M (2007) XANES analysis of Fe valence in iron gall inks. X-Ray Spectrom 36:199–205CrossRefGoogle Scholar
  3. Baldi F, Minacci A, Pepi M, Scozzafava A (2001) Gel sequestration of heavy metals by Klebsiella oxytoca isolated from iron mat. FEMS Microbiol Ecol 36:169–174PubMedCrossRefGoogle Scholar
  4. Baldi F, Marchetto D, Battistel D, Daniele S, Faleri C, De Castro C, Lanzetta R (2009) Iron-binding characterization and polysaccharide production by Klebsiella oxytoca strain isolated from mine acid drainage. J Appl Microbiol 107:1241–1250PubMedCrossRefGoogle Scholar
  5. Baldi F, Marchetto D, Zanchettin D, Sartorato E, Paganelli S, Piccolo O (2010) A bio-generated Fe(III)-binding exopolysaccharide used as new catalyst for phenol hydroxylation. Green Chem 12:1405–1409CrossRefGoogle Scholar
  6. Coe EM, Bowen LH, Speer JA, Wang Z, Sayers DE, Bereman RD (1995) The recharacterization of a polysaccharide iron complex (Niferex). J Inorg Biochem 58:269–278PubMedCrossRefGoogle Scholar
  7. Dominko R, Sirisopanaporn C, Masquelier C, Hanzel D, Arčon I, Gaberscek M (2010) On the origin of the electrochemical capacity of Li2Fe0.8Mn0.2SiO4. J Electrochem Soc 157:A1309–A1316CrossRefGoogle Scholar
  8. Küzma M, Dominko R, Hanzel D, Kodre A, Arčon I, Meden A, Gaberscek M (2009) Detailed in situ investigation of the electrochemical processes in Li2FeTiO4 cathodes. J Electrochem Soc 156:A809–A816CrossRefGoogle Scholar
  9. Leone S, De Castro C, Parrilli M, Baldi F, Lanzetta R (2007) Structure of the iron-binding exopolysaccharide produced anaerobically by the gram-negative bacterium Klebsiella oxytoca BAS-10. Eur J Org Chem 31:5183–5189CrossRefGoogle Scholar
  10. Ravel B, Newville M (2005) ATHENA, ARTEMIS, HEPHAESTUS: data analysis for X-ray absorption spectroscopy using IFEFFIT. J Synchrotron Radiat 12:537–541PubMedCrossRefGoogle Scholar
  11. Rehr JJ, Albers RC, Zabinsky SI (1992) High-order multiple-scattering calculations of x-ray-absorption fine structure. Phys Rev Lett 69:3397–3400PubMedCrossRefGoogle Scholar
  12. Watt RK (2011) The many faces of the octahedral ferritin protein. Biometals 24:489–500PubMedCrossRefGoogle Scholar
  13. Wong J, Lytle FW, Messmer RP, Maylotte DH (1984) K-edge absorption spectra of selected vanadium compounds. Phys Rev B 30:5596–5610CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media, LLC. 2012

Authors and Affiliations

  • Iztok Arčon
    • 1
    • 2
    Email author
  • Oreste Piccolo
    • 3
  • Stefano Paganelli
    • 4
  • Franco Baldi
    • 4
  1. 1.University of Nova GoricaNova GoricaSlovenia
  2. 2.Institut Jozef StefanLjubljanaSlovenia
  3. 3.SCSOPSirtoriItaly
  4. 4.Dipartimento di Scienze Molecolari e NanosistemiUniversità Ca’ Foscari VeneziaVeniceItaly

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