@misc{oai:repo.qst.go.jp:00070922,
 author = {Ishii, Nobuyoshi and Uchida, Shigeo and 石井 伸昌 and 内田 滋夫},
 month = {Sep},
 note = {The long-lived B-emitter technetium-99 (Tc-99) is a man-made fission product of U-235 and Pu-239 with a relatively high fission yield of about 6%.  In aerobic environments, Tc is normally present in a heptavalent form as pertechnetate (TcO4-).  It has been thought that phytoplankton is unsuitable for remediation of Tc-99 contaminated waters.  In this study, removal of Tc-99 by freshwater phytoplankton Euglena gracilis was described.
E. gracilis was cultured in a solution containing Tc-99 for 63 days at 20C under 12 h light-dark cycles.  Removal of Tc-99 from the solution was periodically determined using a Tri-Carb 2500TR liquid scintillation analyzer.  Spirulina platensis (NIES-39), Chlamydomonas pulsatilla (NIES-122) and Chlorella vulgaris (NIES-227) were also tested for the removal of Tc-99.
Among phytoplankton used, only E. gracilis removed significant amounts of Tc-99 from the solution as they grew.  The removal continued for 50 days, at which time equilibrium was achieved.  The maximum value of the removal was 70% of the total Tc-99 added.  To clarify the intracellular uptake of Tc-99 by E. gracili, the removal of Tc-99 by killed cells was carried out.  E. gracilis cells were killed by the addition of a protein synthesis inhibitor cycloheximid at a final concentration of 50 ug mL-1 or by heating cells at 60C for 1 hour.  In both cultures, E. gracilis removed negligible amounts of Tc-99.  In addition to the killed cells experiment, desorption of Tc-99 from cell surface were carried out.  As the pH of the solution was increased from 3.5 to 7.5, a slight increase in desorption amounts of the Tc-99 was observed.  The relative amount of desorption, however, was, at a maximum, 14% of the total Tc-99 removed.  These results suggest that a slight amount of Tc-99 had been adsorbed onto the cell surface.  Results of both the killed cell experiments and desorption experiments show that the removal of Tc-99 by E. gracilis was primarily the result of intracellular uptake., SETAC Asia Pacific 2012 Meeting},
 title = {Removal of technetium-99 by Euglena gracilis},
 year = {2012}
}