IMPROVEMENT OF DOCOSAHEXAENOIC ACID PRODUCTION IN A CULTURE OF THRAUSTOCHYTRIUM-AUREUM BY MEDIUM OPTIMIZATION

Growth optimization of a docosahexaeneic acid (DHA) producing marine f ungus, Thraustochytrium aureum (ATCC 34304), resulted in cell producti vity of 5.7 g/l and 460 mg/l of total lipid in 69 h flask culture, alm ost twice the level of cell productivity obtained for the strain repor ted previously. The lipid extracted from the cells was primarily compo sed of triacylglycerol and contained about 40% DHA. The fermenter cult ure showed a lower growth rate than the flask culture indicating growt h inhibition due to mechanical stirring. Cells grown in the fermenter showed a coagulant tendency. ATCC 34304, in culture, seems to reproduc e asexually and the life cycle of the cells consists of a zoospore sta ge, trophic cell stage and sporangium stage. Zoospore release was obse rved once during the early growth phase throughout growth period both in flask and fermenter culture.