Effect of Dissolved Oxygen Partial Pressure on the Accumulation of Astaxanthin in Chemostat Cultures of Haematococcus Lacustris (Chlorophyta)

The effect of dissolved oxygen partial pressure on the accumulation of astaxanthin in the green alga Haematococcus lacustris (Gir.) Rostaf (UTEX16) was studied in N‐limited continuous chemostat cultures. The steady‐state astaxanthin content measured against culture volume, cell number, and biomass dry weigh of Haematococcus cultures was proportional to the dissolved O2 partial pressure in the culture medium, over the range of 0–50% O2 The steady‐state biomass dry weight concentrations remained at between 0.52 and 0.57 g. L‐1 over the range of dissolved O2 partial pressure studied. Steady‐state cell densities at dissolved O2 partial pressures above the air saturation level (1.13–1.58 × 105 cells.mL‐1) were about half of that measured at lower dissolved O2 partial pressures (2.42–2.63 × 105 cells.mL‐1). Both biflagellated zoospores and nonmotile aplanospores were found at steady state. The fraction of nonmotile cells was higher at dissolved O2 partial pressures above the air saturation level (94.44–98.01%) than at dissolved O2 partial pressure below the air level (79.64–86.12 and 91.75%).