Isolation of Streptomycessp. Absorbing Ytterbium Preferentially and its Absorption Properties

Abstract

To establish a bioprocess using microorganisms for isolation and purification of rare earth elements, we screened some microorganisms by decreasing more than 80% of the Sc, Ce, Sm or Yb in the culture broth. One mold for Sc, 2 bacteria and 1 actinomycete for Ce, 2 molds for Sm, and 1 bacterium and 2 actinomycetes for Yb were isolated. All of the isolates for Sc, Ce, and Sm decreased the rare earth elements tested. However, one actinomycete, strain YB-2733, for Yb decreased preferentially heavy rare earth elements such as Tm and Lu, as well as Yb. This strain decreased Y, of which the atomic radius is similar to those of heavy rare earth elements, suggesting that this strain could recognize atomic radii of rare earth elements. The YB-2733 was identified as Styeptomyces sp.based on morphological observation and phylogenetic analysis of 16S ribosomal DNA. Styeptomyces sp. YB-2733 contained 5-7 mg Yb per g dry cells. Yb was distributed in cell wall fraction, cell extract, and cell membrane fraction, 7%, 9%, and 84%, respectively. The Yb content in the cell membrane fraction was 22-28mg per g dry membrane fraction. The Yb in the membrane fraction was completely released by treatment of 1 mM EDTA, but HCl, NaOH and NaCl at 1 M, and Triton-X (0.5%) and sodium dodecyl sulfate (0.4%) did not release Yb sufficiently. Yb was also released from Yb-adsorbed cells by the treatment of 1 mM EDTA. We showed that the cells and the cell membrane fraction of Styeptomyces sp. YB-2733 were repeatedly used at least 5 times as an Yb adsorbent.