Bioproduction of Docosahexaenoic Acid by the Marine protist Schizochytrium

Abstract

The heterotrophic protist Schizochytrium sp. was batch cultivated in media containing glucose, yeast extract, peptone, dihydrogen potassium phosphate and sea salt prepared in distilled water. The increasing amounts of yeast ex-tract stimulated growth however, influenced lipid accumulation negatively. It has been observed that the sea salt concentrations above half the average seawater salinity were required for good growth and lipid accumulation. Schizochytrium sp. was able to grow on a glucose concentration as high as 60 g/l, which resulted in reduced biomass and lipid yield. Although, the culture in study, effectively utilized certain simple and complex nitrogen sources lipid yield was more in complex nitrogen source, i.e. yeast extract and pep-tone, than in simple nitrogen source. Comparison of growth at 20 and 28 ºC showed that the higher incubation temperature was more favorable for the growth. The optimum pH was optimized as 7 with a rotation speed of 220 rpm. Incubation for 120 h was required for the maximum production of bio-mass, lipid and DHA. In this period, the percentage of docosahexaenoic acid (20.0 %) was produced in the lipid (4.0 g/l).