For cultivation the reactor was inoculated with a stock culture to a concentration of approximately 7 × 108 cells L−1 . During the growth phase an average incoming light intensity was used of 200 mol photons m−2 s−1 . By gassing the cell suspen- sion via an inlet tube at the bottom of the reactor with nitrogen gas (0.6 L min−1 ) mixing of the culture and oxygen removal were established. As a cell number of 1.6 × 109 cells L−1 was reached, the culture was diluted to reach 0.8 × 109 cells L−1 with a total volume of the aqueous phase of 1.9 L (referred to as LRV ). Simultaneously the light intensity was increased to 1200 mol photons m−2 s−1 .