EFFECTS OF NITROGEN-SOURCE AND GROWTH-PHASE ON PROXIMATE BIOCHEMICAL-COMPOSITION, LIPID CLASSES AND FATTY-ACID PROFILE OF THE MARINE MICROALGA ISOCHRYSIS-GALBANA

The marine microalga Isochrysis galbana was cultured in nitrate, nitri te or urea media to examine changes in the gross biochemical compositi on, with special emphasis on the growth phase associated changes in th e compositions of the lipid classes and fatty acids. The gross biochem ical composition was affected more by the growth phase than by the nit rogen source. Protein was higher during exponential growth (about 37-4 5% AFDW) but the pattern changed as the cultures aged, and lipids were the main algal constituents on all nitrogen sources in the late stati onary phase. In all cultures, the relative abundance of neutral lipid increased in the late stationary phase concomitant with a proportional reduction in phospholipids, whereas galactolipids only slightly chang ed during the growth of the cultures. Total fatty acid content was aff ected by nitrogen source and growth phase. Maximal PUFA values were ob tained at the early stationary phase and decreased throughout the stat ionary phase. The highest fatty acid contents in the early stationary phase were produced in urea cultures; these cultures also had higher P UFA content, with EPA and DHA contents of 27.66% and 14.13% of total f atty acids, respectively. (C) 1998 Elsevier Science B.V. All rights re served.