Fig. 3

Growth (cells mL⁻¹) of cultures of C. vulgaris cultured under various inorganic carbon regimes. (Square) Continuous sparge of atmospheric air, (triangle) continuous sparge of atmospheric air and supplemented with 5 mM NaHCO₃ at inoculation, (circle) continuous sparge of atmospheric air supplemented periodically with 5 % CO₂ (v/v) to maintain pH between 8.4 and 8.7, (diamond) continuous sparge of atmospheric air supplemented with 5 % CO₂ (v/v) during daytime hours, and (right pointing triangle) the optimized scenario of a continuous sparge of atmospheric air supplemented periodically with 5 % CO₂ (v/v) to maintain pH between 8.4 and 8.7 and an initial addition of 5 mM NaHCO₃ at inoculation plus an additional 50 mM NaHCO₃ just prior to nitrogen depletion to stimulate TAG accumulation (n = 3). Arrow indicates time of 50 mM NaHCO₃ addition just prior to nitrogen depletion of the culture medium