n-3 PUFA productivity in chemostat cultures of microalgae

Eicosapentaenoic (EPA) and docosahexaenoic (DHA) acid productivities from chemostat cultures of an isolate of Isochrysis galbana have been studied. The productivities reached in the interval of dilution rates between 0.0295 h^-1 and 0.0355 h^-1 were 1.5mg·1^-1·h^-1 for lipids, 300 μg·1^-1·h^-1 for EPA and 130μg1·1^-1·h^-1 for DHA. Furthermore, light attenuation by mutual shading, and agitation speed influences on growth and fatty acid composition were analysed. A model relating steady-state dilution rates to internal average light intensity has been proposed, the parameter values of which obtained by non-linear regression were: maximum specific growth rate (μ_max)=0.0426 h^-1; the affinity of cells to light (I_k) = 10.92 W·m^-2; the exponent (n) = 5.13; regression coefficient (r²)=0.9999.