Effects of twenty standard amino acids on biochemical constituents, docosahexaenoic acid production and metabolic activity changes of Crypthecodinium cohnii.

The influence of 20 standard amino acids was investigated on growth, lipid accumulation, docosahexaenoic acid (DHA) production and cell biochemical composition of Crypthecodinium cohnii. C. cohnii efficiently utilize organic nitrogen (predominantly threonine and to a lesser extent tyrosine and serine) as compared to inorganic nitrogen (NH4 )2 SO4 . However, No significant effect was observed on major biochemical composition of C. cohnii (lipids, carbohydrates and proteins) under N limitation or supplementation with different N-sources. Key lipogenic enzymes glucose-6-phosphate dehydrogenase, ATP-citrate lyase, fatty acid synthase, malic enzyme, citrate synthase (CS), NAD+ and NADP+ dependent isocitrate dehydrogenase were shown to be vital in lipogenesis of C. cohnii. Our results indicated that the process of lipid accumulation in C. cohnii is growth-associated and does not depend upon the trigger of nitrogen depletion. This unusual behavior would suggest that the metabolism of the cells may not be entirely the same as in other lipid-accumulating microorganisms.