Long-chain n-3 polyunsaturated fatty acid production by members of the marine protistan group the thraustochytrids: screening of isolates and optimisation of docosahexaenoic acid production

Following an isolation programme for thraustochytrids (marine fungoid proti sts) from three different locations, 57 isolates were screened for biomass, oil and docosahexaenoic acid production (DHA). Although a common fatty aci d profile for the thraustochytrid isolates emerged, there was considerable variation in the DHA content of the oil. In some isolates from a cold tempe rate environment, DHA represented almost 50% of the total fatty acids prese nt. Although isolates from a sub-tropical environment produced higher level s of biomass, with up to 37% (w/w) oil, the DHA fraction of the fatty acids was low. Cool temperate isolates gave intermediate values. Studies to opti mise biomass and DHA production by manipulation of growth medium compositio n were carried but on a tropical strain. Results indicated that medium with a high C:N ratio stimulated DHA production. The use of such media in biore actor cultivations gave maximum biomass, lipid and DHA content of 14 g l(-1 ), 78 and 25% (w/w), respectively. Optimum DHA production was 2.17 g l(-1) after 107 h cultivation. (C) 1999 Elsevier Science B.V. All rights reserved .