Sterol composition of phaeodactylum tricornutum as influenced by growth temperature and light spectral quality.

In a detailed sterol analysis of the marine diatom Phaeodactylum tricornutum, free sterols as well as esterified and glycosylated conjugates were found. When the alga was grown under standard conditions (i.e., at 13 degrees C under white light), 64% of total sterols were steryl glycosides. In all sterol classes, except steryl esters, (24S)-24-methylcholesta-5,22E-dien-3 beta-ol (epibrassicasterol) was the major (80 to 99%) sterol component. Eight other sterols were identified. Growth under different light spectral quality (red, blue, yellow, and green) at 13 and 23 degrees C was examined. At 23 degrees C, a dramatic decrease in total sterol content was observed, especially under blue light. The distribution of sterols between free and conjugated forms as well as sterol profile inside each class was found to be strongly dependent on the light spectral quality at both temperatures.