Effects of temperature and temperature shift on docosahexaenoic acid production by the marine microalga Crypthecodinium cohnii

The effects of temperature and temperature shift on the fatty acid composition and docosahexaenoic acid (DHA, C22:6n-3) content and productivity of the marine microalga Crypthecodinium cohnii ATCC 30556 were investigated. The microalga grew well over the entire range of temperatures (15-30 degrees C) studied. High temperature favored the growth of the microalga with the highest specific growth rate of 0.092 h(-1) at 30 degrees C. In contrast, low temperature favored the formation of polyunsaturated fatty acids. The highest DHA content was obtained at 15 degrees C in the early stationary phase (i.e., 72 h). In order to achieve high DHA productivity, a shift from high temperature to tow temperature at a later stage of cultivation (i.e., 48 h) was also attempted. A temperature shift from 25 degrees C (for 48 h) to 15 degrees C (for 24 h) resulted in an increase in cellular DHA content by 19.9% and productivity by 6.5% as compared to that maintained at 25 degrees C (for 72 h).