Characteristics of Growth and Deuterium Incorporation in Chlorella ellipsoidea Grown in Deuterium Oxide

Abstract

The effect of deuterium oxide (D₂O) was examined on the cell growth of photoautotrophically growing Chlorella ellipsoidea. The growth rate was inversely proportional to the concentration of D₂O in the medium up to 60 mol%. The growth in D₂O medium at concentrations higher than 60 mol% was highly inhibited. However, the cells pre-cultured in 60 mol% D₂O medium became able to grow even in practically 100 mol% D₂O medium. Deuterium (D) was incorporated into cells proportionally to the concentration of D₂O in the medium. The D/H ratio in the cells was lower than that of the cultivation medium. Chlorella cells cultured in practically 100 mol% D₂O medium contained ca. 70 mol% D. Of the D incorporated into cells, about 20% was easily exchangeable with H, and the remaining 80% was unexchangeable.