Effects of lowering temperature during culture on the production of polyunsaturated fatty acids in the marine diatom Phaeodactylum tricornutum (Bacillariophyceae)

The composition of fatty acids and contents of eicosapentaenoic acid (EPA) and polyunsaturated fatty acids (PUFAs) of the economically important marine diatom, Phaeodactylum tricornutum (Bohlin), were investigated to see whether reducing the culture temperature enhances the production of EPA and PUFAs. The contents of EPA and PUFAs of P. tricornutum were found to he higher at lower temperature when cultured at 10, 15, 20, or 25degrees C. When the cells grown at 25degrees C were shifted to 20, 15, or 10degrees C, the contents per dry mass of PUFAs and EPA increased to the maximal values in 48, 24, and 12 h, respectively. The highest yields of PUFAs and EPA per unit dry mass (per unit volume of culture) were 4.9% and 2.6% (12.4 and 6.6 mg (.) L-1), respectively, when temperature was shifted from 2 5 to 10degrees C for 12 h, both being raised by 120% compared with the control. The representative fatty acids in the total fatty acids, when temperature was lowered from 25 to 10degrees C, decreased proportionally by about 30% in C-16:0 and 20% in C16:1(n-7) but increased about 85% in EPA. It was concluded that lowering culture temperature of P tricornutum could significantly raise the yields of EPA and PUFAs.