, Volume 11, Issue 6, pp 859-867
Date: 03 Aug 2007

Microbial formation of lanthanide-substituted magnetites by Thermoanaerobacter sp. TOR-39

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The potentially toxic effects of soluble lanthanide (L) ions, although microbially induced mineralization can facilitate the formation of tractable materials, has been one factor preventing the more widespread use of L-ions in biotechnology. Here, we propose a new mixed-L precursor method as compared to the traditional direct addition technique. L (Nd, Gd, Tb, Ho and Er)-substituted magnetites, L y Fe3 − y O4 were microbially produced using L-mixed precursors, L x Fe1 − x OOH, where x = 0.01–0.2. By combining lanthanides into the akaganeite precursor phase, we were able to mitigate some of the toxicity, enabling the microbial formation of L-substituted magnetites using a metal reducing bacterium, Thermoanaerobacter sp. TOR-39. The employment of L-mixed precursors enabled the microbial formation of L-substituted magnetite, nominal composition up to L0.06Fe2.94O4, with at least tenfold higher L-concentration than could be obtained when the lanthanides were added as soluble salts. This mixed-precursor method can be used to extend the application of microbially produced L-substituted magnetite, while also mitigating their toxicity.