BIOMASS AND ICOSAPENTAENOIC ACID PRODUCTIVITIES FROM AN OUTDOOR BATCHCULTURE OF PHAEODACTYLUM-TRICORNUTUM UTEX-640 IN AN AIRLIFT TUBULAR PHOTOBIOREACTOR

An outdoor tubular photobioreactor, based on an external-loop airlift, has been used to cultivate the diatom Phaeodactylum tricornutum UTEX 640, rich in icosapentaenoic acid (EPA). The system was operated in ba tch mode. The specific growth rate in the exponential phase, averaged over the whole day, was 0.254 day(-1). A 25 gl(-1) maximum biomass con centration was obtained by the end of the culture period. The dissolve d oxygen generated never rose over 210% of air saturation nor was ther e impediment to biomass generation or inhibition of photosynthesis. Fu rthermore, around 2 x 10(17) quanta cm(-2) s(-1) light intensity seeme d to saturate the photosynthetic activity. Biomass losses during the n ight could be reduced to less than 5% by maintaining the culture at 16 degrees C at night. The maximum concentration and productivity of EPA were 423 mgl(-1) and 13 mgl(-1)day(-1), respectively, at the end of t he culture, although a 21-mgl(-1)day(-1) net EPA generation rate was o btained at the linear growth phase.