STEROL COMPOSITION OF PHAEODACTYLUM-TRICORNUTUM AS INFLUENCED BY GROWTH TEMPERATURE AND LIGHT SPECTRAL QUALITY

In a detailed sterol analysis of the marine diatom Phaeodactylum trico rnutum, 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 g lycosides. In all sterol classes, except steryl esters, (24S)-24-methy lcholesta-5,22E-dien-3 beta-ol (epibrassicasterol) was the major (80 t o 99%) sterol component. Eight other sterols were identified. Growth u nder different light spectral quality (red, blue, yellow, and green) a t 13 and 23 degrees C was examined. At 23 degrees C, a dramatic decrea se 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.