Effects of temperature and growth phase on lipid and biochemical composition of Isochrysis galbana TK1

The lipid and biochemical composition of the haptophyte Isochrysis galbana TK1 was examined. Cultures were grown at 15 degrees C and 30 degrees C, and harvested in the exponential and early stationary growth phases. Carbohydrate and protein content varied at the two culture temperatures and growth phases. The highest protein content was found at the exponential growth phase at 15 degrees C, and the highest carbohydrate content was found at the stationary phase at the same culture temperature. Lipid accumulated in the stationary growth phase and its content was higher at 30 degrees C than at 15 degrees C regardless of the growth phase. The neutral lipids were the major class of lipid found in all the cultures. The stationary phase culture had a higher proportion of neutral lipids than the exponential phase culture and the proportion decreased slightly when culture temperature was increased from 15 degrees C to 30 degrees C. Phospholipid levels remained constant at the two temperatures, but slightly decreased in the stationary phase. Glycolipids in the exponentially growing cells were higher than those from stationary growth phase and increased with temperature. Polyunsaturated fatty acids (PUFAs) predominated in glycolipids and phospholipids. Cells grown at 15 degrees C contained higher proportion of 18:3 (n-3) and 22:6 (n-3) with a corresponding decrease in 18:2 (n-6), monounsaturated and saturated fatty acids.