A New Fungal Isolate, Penidiella sp. Strain T9, Accumulates the Rare Earth Element Dysprosium

Abstract

With an aim to develop a highly efficient method for the recovery of rare earth elements (REEs) by using microorganisms, we attempted to isolate dysprosium (Dy)-accumulating microorganisms that grow under acidic conditions from environmental samples containing high concentrations of heavy metals. One acidophilic strain, T9, which was isolated from an abandoned mine, decreased the concentration of Dy in medium that contained 100 mg/liter Dy to 53 mg/liter Dy after 3 days of cultivation at pH 2.5. The Dy content in the cell pellet of the T9 strain was 910 g/mg of dry cells. The T9 strain also accumulated other REEs. Based on the results of 28S-D1/D2 rRNA gene sequencing and morphological characterization, we designated this fungal strain Penidiella sp. T9. Bioaccumulation of Dy was observed on the cell surface of the T9 strain by elemental mapping using scanning electron microscopy-energy dispersive X-ray spectroscopy. Our results indicate that Penidiella sp. T9 has the potential to recover REEs such as Dy from mine drainage and industrial liquid waste under acidic conditions. T he rare earth elements (REEs), which include scandium (Sc; atomic number [Z] ϭ 21), yttrium (Y; Z ϭ 39), and the 15 lanthanide elements (Z ϭ 57 to 71), exhibit magnetism, fluorescence, and superconductivity due to their characteristic electron orbitals (1). As powerful magnetic and superconductive materials are essential for the development of advanced industries that require high-energy efficiency, REEs are indispensable ingredients in the manufacture of these products. Dysprosium (Dy) is marketed at a higher rate than other REEs due to its limited resources and the expanding demand for this heat-resistant, powerful magnetic material. To establish new sources of Dy, even wastes with low Dy concentrations, such as mine drainage, ore wastes, and industrial liquid wastes, have been gaining attention (2, 3). However, systems to efficiently recover Dy from these wastes using physical/chemical technologies have not yet been developed. Therefore, new technologies for the recovery of Dy from wastes with low Dy concentrations are urgently needed.Biological approaches based on bioaccumulation by microorganisms have recently received a great deal of attention as alternatives for metal recovery and remediation (4). Compared to physical/chemical technologies, bioaccumulation has the advantages of low cost, high efficiency, and environmental friendliness (5, 6). Although the resting cells of several microorganisms have been shown to accumulate REEs at pH 3.0 to 6.0 (7,8,9,10), no microorganism has been shown to accumulate REEs at pH values below 3.0. In this study, we attempted to isolate microorganisms from environmental samples that have the ability to accumulate Dy (during growth) from acidic wastewater containing dissolved Dy similar to that found in mine drainage. One such strain isolated from an abandoned mine site was analyzed by phylogenetic and morphological methods and was found to belong to the fungal division Ascomycota. Dy bioaccumulation ...

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