Accumulation of Co in Yeast Cells under Metabolically Active Condition—Implication for Role of Yeast in Migration of Radioactive Co—

Abstract

The accumulation and change in the chemical states of Co have been studied to elucidate the role of the yeast Saccharomyces cerevisiae in the migration of radioactive cobalt in the environment. The yeast was grown in a solution containing Co(II) ions, a carbon source, and essential elements (metabolically active condition). For comparison, an adsorption experiment of Co(II) ions on the yeast cells under resting condition without essential elements was performed. Time courses of Co concentration in the solution, in the cells, and chemical states of the accumulated Co were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES), particle-induced X-ray emission (PIXE), and X-ray absorption fine structure (XAFS) analyses. The time courses of Co concentration in the solution showed that a higher amount of Co was accumulated by the yeast cells under the metabolically active condition than under the resting one. PIXE analyses showed the concurrent accumulation of Fe with Co accumulation under the metabolically active condition, suggesting the intracellular accumulation of Co. XAFS analyses showed that the k 3 -weighted extended-XAFS functions and the radial structural function of Co accumulated by the yeast cells under the metabolically active condition are similar to those under the resting condition, indicating that the chemical states of the accumulated Co were nearly the same between both conditions. These results indicate that the yeast performs better retardation of the migration of Co under the metabolically active condition than under the resting one.

The radiation resistance and cobalt biosorption activity of yeast strains isolated from the Lanyu low-level radioactive waste repository in Taiwan

“…Although a great number of microbial species might be used as biosorbents for the removal of heavy metals and radionuclides from waste, we believe that yeast strains have many features that make them more effective than other microbial species as biosorbents for heavy metals and radionuclides. The physiological transport of essential elements, including Co, by yeast is well known (Kozai et al, 2011;Walker, 1998), and the radioactive isotope of 60 Co is one of the major radionuclides in the LLRW in Taiwan. However, the radionuclides that accumulate in the yeast biomass should be the cause of most concern.…”