Optimal renewal rate and nutrient concentration for the production of the marine microalga Phaeodactylum tricornutum in semicontinuous cultures

A factorial experiment comprising sis nutrient concentrations and six renewal rates was set to optimize semicontinuous cultures of Phaeodactylum tricornutum. Maximal cell density, 85 x 10(6) cells ml(-1), was obtained with 8 and 16 mmol of N per liter and a renewal rate of 10%. Protein stabilized at about 60% of the organic fraction for nitrogen-sufficient cultures. Both lipids and carbohydrates were stored as energetic reserves.