n-3 Polyunsaturated fatty acid productivity of the marine microalgaIsochrysis galbana. Growth conditions and phenotypic selection

Two set of isolates were obtained in an isolation/selection programme to select eicosapentaenoic acid (EPA) and/or docosahexaenoic acid (DHA) rich strains ofIsochrysis galbana. EPA content was improved up to an average of 5.3% (d.wt) for the second set of isolates. On the other hand, with the aeration rate, pH and irradiance kept at low levels, the growth rate was slow and EPA synthesis was enhanced, but productivity increased when growth rates were maximum. A model relating steady-state dilution rates in chemostat cultures ofI. galbana to internal average irradiance is proposed. The greatest productivities were obtained between 0.0295 h^–1 and 0.0355 h^–1 with 300 mg m^–3 h^–1 for EPA and 130 mg m^–3 h^–1 for DHA.