Fungus-promoted transformation of lanthanides during the biooxidation of divalent manganese

Although microorganisms possess high sorption capability for lanthanides, the effect of their biological response on lanthanides migration is unclear. Using active fungus Acremonium strictum KR21-2, supplied with nutrients, this study compared the transformation of lanthanides during the biooxidation of Mn(II) in the absence and presence of trisodium citrate. In the absence of trisodium citrate, lanthanides were rapidly sorbed on fungal cells within 24 h, followed by the preferential desorption of Ce over other lanthanides as Mn oxide formed. Most of the desorbed Ce was in the colloidal phase and associated with a biomolecule produced by the active fungus. In contrast, neither desorption of Ce nor release of this biomolecule occurred in the presence of trisodium citrate. Most importantly, the Ce-binding biomolecule was not found to associate with any other trivalent lanthanides tested or with Fe. The biomolecule was characterized as c.a. 4700 Da in size, and it contains saccharides that differed from those non-nuclide-specific organic substances released from resting cells, as reported previously. This study highlights the importance of biotic reactions between lanthanides and microbial cells, which may affect the migration of lanthanides at the water-Mn oxide interface. (c) 2015 Elsevier Ltd. All rights reserved.