Outdoor cultivation of the marine microalga Isochrysis galbana in open reactors

Experiments concerning the optimization of growth conditions in the laboratory and mass production of the marine microalga Isochrysis galbana in open reactors are described. In the laboratory, a maximum specific growth rate (μmax) of 0.073 h^-1 was obtained, which is equivalent to a doubling time of 9.5 h. In a small reactor (2.5-m² pond) the production rate of biomass was 29.5±2 g m^-2 day^-1 and that of lipids was 6.5±0.5 g m^-2 day^-1. In a larger reactor (100-m² pond) in which algae were grown first by batch and then by semi-continuous mode, the average output rates of biomass and of lipids were 23.5±1.5 g m^-2 day^-1 and 5.6±0.5 g m^-2 day^-1, respectively. A complete removal of the biomass was achieved in the 100-m² pond by means of flocculation with FeCl₃ (180 mg l^-1) and dissolved air flotation without a prior recycling of part of the effluent. Monoalgal cultures were maintained in the different outdoor experiments throughout the entire 4-month production period.