Particulate and dissolved lipid classes in cultures of Phaeodactylum tricornutum grown in cage culture turbidostats with a range of nitrogen supply rates

Abstract

Production of intracellular and extracellular algal lipid classes wasexa mined over a range of rates of supply of inorganic nitrogen. The marine diatom Phaeodactylum tricornutum was studied using 2 new techniques. Cage culture turbidostats were used for growing the phytoplankton. These are continuous culturing systems which provide a highly controlled algal environment. The Chromarod-Iatroscan TLC/FID system was used for lipid class separation and quantification. This permitted the resolution and detection of as many as 10 algal lipid classes plus an internal standard for accurate quantification. Up to 3 culturing units were supplied with medium of known nutrient content simultaneously, and particulate intracellular lipids together with dissolved lipids in the effluent media were monitored. Intracellular synthesis of a storage class, triglyceride, was clearly triggered by nitrogen stress, while synthesis of membrane-associated polar lipid classes was reduced under these conditions. Particulate triglyceride yield was higher at lower levels of nitrogen supply despite lower growth rates. Different amounts and different types of dissolved extracellular lipid classes were produced under nitrogen-stressed and nitrogen-replete conditions.