Production of polyunsaturated fatty acids in semicontinuous cultures of marine microalgae
1997
Fabregas, Jaime | Barcoa, Digna | Otero, Ana(National Institute for Basic Biology, Okazaki (Japan))
We report here the changes in the fatty acid composition of three species of marine microalgae: Isochrysis galbana, Phaeodactylum tricornutum and Porphyridium cruentum, cultured semi-continuously. The degree of unsaturation of fatty acids increased with increasing renewal rate for the three species. In I. galbana, maximal EPA productivity, 4.6 mg/l/day, was achieved with intermediate renewal rates and a nutrient concentration of 4 mg atom N/l. In this species EPA cellular content increased with renewal rate despite the decrease of total fatty acid content of cells. On the other hand, the dramatic decrease in cell lipid content with increasing renewal rates forced a decrease in EPA cellular content in Phaeodactylum tricornutum. Maximal EPA productivity obtained for this species was 5.2 mg/l/day. Similar EPA productivity, 5.3 mg/l/day, was obtained with Porphyridium cruentum cultured with a renewal rate of 50 percent and 16 mg atom N/l. In P. cruentum EPA was substituted by arachidonic acid at low dilution rates, reaching a productivity of 7 mg/l/day with a renewal rate of 20 percent. DHA content in I. galbana and P. tricornutum was not so strongly affected by renewal rate and nutrient concentration as EPA content, reaching productivities of 1.4 and 0.35 mg l day respectively. Results indicate that different culture strategies should be adopted for the production of a particular polyunsaturated fatty acid depending on the microalgal species being used.
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