An intensive continuous culture system using tubular photobioreactors for producing microalgae

Growth and productivity of marine microalgae, Chlorella Strain MFD-1 and Nannochloropsis Strain MFD-2, in an intensive continuous culture system using 200-1 capacity translucent vertical air-lift tubular photobioreactors is described. Using a culture surface irradiance of 330 μE m^-2 s^-1 and at a controlled pH of 6.5 and 7.0, the productivity varied between 109 and 264 g m^-3 d^-1 with a mean of 169.7±34.7 g m^-3 d^-1 for Chlorella Strain MFD-1 and between 32.5 and 95.3 g m^-3 d^-1 with a mean of 50.6±14.2 g m^-3 d^-1 for Nannochloropsis Strain MFD-2. The productivity of microalgae in relation to different light intensities is discussed. The fatty acid composition, especially the ω3 Highly Unsaturated Fatty Acids (ω3 HUFA), of these microalgae is species-dependent in the culture system. The total ω3 HUFA and the essential fatty acid eicosapentaenoic acid (EPA) content were significantly higher (P<0.001) in Nannochloropsis Strain MFD-2 compared to Chlorella Strain MFD-1, showing that the former is more suitable for aquacultural purposes since EPA is mandatory for the feeding of marine fish larvae. The algal productivity obtained in the present culture system is considerably higher than with the conventional methods described to date for aquacultural purposes.