Comprehensive Study of Cultivation Conditions and Methods on Lipid Accumulation of a Marine Protist, Thraustochytrium striatum

This research studied the influences of cultivation conditions (carbon/nitrogen source concentration, initial pH, salinity, and rotation speed) on cell growth and fatty acid (FA) production/composition of a marine protist, Thraustochytrium striatum. Fed-batch was also studied to improve cell growth and FA production. The optimum cell growth (∼5 g/L dry cell mass, DCM) occurred under the cultivation conditions of T = 25 °C, glucose = 30 g/L, yeast extract/peptone (YEP) = 4 g/L, salinity = 100% of seawater, pH = 6-7, and rotation speed = 120 rpm. Starch/glycerol and yeast extract were the best carbon and nitrogen sources, respectively for achieving the maximum cell growth. Low carbon/nitrogen (C/N) ratio benefited cell growth while high C/N ratio was conducive to FA accumulation. The maximum lipid content of 25% (g/g DCM) was obtained at glucose/YEP of 30/1 (w/w). Starch and ammonia chloride were suggested to be used as carbon and nitrogen sources. Compared to batch, fed-batch increased FA content significantly from 27 to 38%, primarily including 35% of C16:0, 42% of C18:1, 9% of C18:2 and 5% of EPA/DHA. The major FAs of T. striatum were palmitic, stearic, oleic, and linoleic acids along with a small amount of docosahexaenoic and eicosapentaenoic acids, which suggests lipid from T. striatum be suitable for biodiesel production.