Growth yield determination in a chemostat culture of the marine microalga Isochrysis galbana

The growth yield of the PUFA-producing marine microalga Isochrysis galbana ALII-grown in a light limited chemostat, was measured under a wide variety of conditions of incident irradiance (Io) and dilution rates (D). The experiments were conducted under laboratory conditions at 20 degrees C under continuous light. D ranged from 0.024 to 0.0410 h(-1) at three intensities of Io (820, 1620, and 3270 mu mol photon m(-2) s(-1)) close to those found in outdoor cultures. A maximum efficiency Psi(max) = 0.616 g mol photon(-1) was obtained at Io = 820 mu mol photon m(-2) s(-1) and D = 0.030 h(-1), and the maximum capacity of the biomass to metabolize the light harvested was found to be 13.1 mu mol photon g(-1) s(-1). Above this value, a significant drop in the system efficiency was observed. A new approach based in the averaged irradiance is used to assess the photon flux absorbed by the biomass.