Isolation of a novel Co²⁺-resistant bacterium and the application of its siderophore in Co²⁺ recovery from an aqueous solution

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Siderophores are considered to have a good potential as decontamination agents owing to their metal-chelating abilities. In order to confirm whether siderophores can be used in the recovery of metal ions, a siderophore (or metallophore) exhibiting Co²⁺-chelating activity was screened to demonstrate its ability to recover Co²⁺ from an aqueous solution. A siderophore-producing bacterium, Pandoraea sp. HCo-4B, was identified from a screen of Co²⁺-resistant bacteria grown in an aerobic enrichment culture with a Co²⁺-supplemented medium. After incubation of the crude extracted siderophore in a Co²⁺-containing solution, the Co²⁺-siderophore complex was adsorbed on to a C₁₈ column. The bound Co²⁺ was eluted from the column by the addition of 10 mM H₂SO₄. The recovered amount of Co²⁺ was proportional to the amount of the added siderophore. We observed that the siderophore identified in this study binds to Co²⁺ at a 1:1 ratio.