Cellular accumulation of cesium in the unicellular red alga Galdieria sulphuraria under mixotrophic conditions

As a consequence of the Fukushima Daiichi Nuclear Power Plant accident which occurred in Japan in 2011, huge amounts of radioactive cesium (Cs) spread across a large area at low concentrations. Bioremediation is known as an effective method for the recovery and concentration of metals at low concentrations. In the present study we showed that G. sulphuraria cells recovered 52 ± 15% of the Cs present in a potassium-deficient medium containing 30 μg L −1 Cs in 10 days. Because of the advantages in biotechnological use, G. sulphuraria is a good candidate for the decontamination of radioactive Cs. In G. sulphuraria cells, Cs was accumulated specifically under mixotrophic condition of the three different culture conditions used (autotorophic, mixotrophic, and heterotrophic condition). Cells in the early logarithmic phase of growth did not accumulate Cs, whereas those in the late logarithmic phase did. Cs accumulated in the cell exists mainly in a soluble form (e.g., salt, chelating complex).