Studies on the accumulation of heavy metal elements in biological systems. Part XV. Accumulation of uranium by Chlorella cells grown under autotrophic, heterotrophic and mixotrophic culture conditions.

Previously we reported that Chlorella regularise one of the fresh water green microalgae, could accumulate a relatively large amount of heavy metal ions such as copper,l ) uranium,2) manganese,3) and cadmium4) from the aqueous systems.So this alga was of particular interest from the points of the regulation of the environmental pollutants and the recovery of the useful metals from the aqueous systems.Our previous experiments were exclusively concerned with autotrophic Chlorella cells.Chlorella regularis could be also grown under heterotrophic and mixotrophic conditions.5)In order to obtain the fundamental information on the recovery of uranium from aqueous systems using Chlorella cells, we determined whether or not the difference of uranium accumulation ability occurred among the cells grown under the different culture conditions, autotrophic, heterotrophic and mixotrophic.Chlorella regularis S-50 was used throughout the