Optimisation of docosahexaenoic acid production in batch cultivations by Crypthecodinium cohnii

The heterotrophic micro alga Crypthecodinium cohnii was cultivated in media containing glucose, yeast extract and sea salt. Increasing amounts of yeast extract stimulated growth but influenced lipid accumulation negatively. Sea salt concentrations above half the average seawater salinity were required for good growth and lipid accumulation. C. cohnii was able to grow on a glucose concentration as high as 84.3 g l-1, although concentrations above 25 g l-1 decreased the growth rate. Comparison of growth at 27 and 30°C showed that the higher incubation temperature was more favourable for growth. However, lipid accumulation was higher at the lower incubation temperature. In a bioreactor the biomass concentration increased from 1.5 to 27.7 g l-1 in 74 h. In the final 41 h of the process the lipid content of the biomass increased from 7.5 to 13.5%. In this period the percentage of docosahexaenoic acid of the lipid increased from 36.5 to 43.6%. The total amounts of lipid and docosahexaenoic acid after 91 h were 3.7 and 1.6 g l-1, respectively. Copyright (C) 1999 Elsevier Science B.V.