Docosahexaenoic acid ethyl esters from Isochrysis galbana

In order to produce docosahexaenoic acid (DHA), a culture of the microalgal strain Isochrysis galbana was implemented. In Erlenmeyer flasks, a natural seawater medium, the Provasoli 1/3 medium, was compared to the classical J ones medium for DHA production. The Provasoli 1/3 medium stimulated growth (0.44 d(-1)), but influenced DHA accumulation negatively (0.240 pg cell(-1) ). However, DHA production per liter of culture medium were of the same ord er of magnitude with both media (0.961 mg l(-1)). In a 2-l bioreactor, DHA production per liter of culture medium did not increase significantly betwe en 4 and 8 days of culture. With a view to optimize DHA productivity, cells should be harvested at the end of exponential phase i.e. after 4 days of c ulture. Two strategies were then attempted to produce DHA ethyl esters. Fir st, lipids from I. galbana were submitted to lipase-catalyzed transesterifi cation with ethanol. Secondly, fatty acids from I. galbana were submitted t o lipase catalyzed esterification with ethanol. In both cases, lipase from Candida antarctica was shown to be the best candidate, among the five teste d, with conversion yields of 20 and 60% after 24 h of transesterification a nd esterification respectively. (C) 2001 Elsevier Science B.V. All rights r eserved.