LIPID PRODUCTION BY PHAEODACTYLUM-TRICORNUTUM

The results of a three month investigation on the outdoor mass culture of Phaeodactylum tricornutum Bohlin are reported. Experiments carried out from January to March 1989 gave an average output rate of 4.0 g m-2 day-1 in ash-free dry weight (AFDW) basis for semicontinuous mode (days 0-74) and 2.0 g m-2 day-1 for batch mode (days 74-84). Eicosapentaenoic acid (20:5 omega-3 EPA) was the predominant fatty acid synthesized by this diatom during semicontinuous growth constituting 3.9% of AFDW, yielding 0.15 g m-2 day-1. The content of EPA was decreased to 0.7% of AFDW during batch mode, 16:0 and 16:1 becoming the main fatty acids. The relationship between optical density and output productivity rate was studied. In the range studied, the lower the concentration the higher the productivity and the lower the lipid production rate. Several flocculant systems were tried and calcium hydroxide, Ca(OH)2, was found to be best at concentrations from 30 to 100 mg litre-1, in an apparently random way. The addition of chitosan did not improve the efficiency of flocculation.