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The microalga Phaeodactylum tricomutum was cultured under various conditions in an external tubular photobioreactor and in a bubble column. The proximate composition (moisture, ash, crude protein, available carbohydrates, fiber, lipids and energy), nitrate, nucleic acids, mineral elements (Na, K, Ca, Mg, Fe, Cu, Zn, Mn, P, S, As, Pb, Cd), C/N ratio, fatty acids and pigments (total carotenoids, carotenoid class and chlorophylls) were analyzed. On average, the biomass contained 36.4% crude protein, 26.1 % available carbohydrates, 18.0% lipids, 15.9% ash and 0.25% neutral detergentfiber, on a diy wt basis. The mineral element contents in 100 g diy biomass were: Ca (1 91 0 mg), K (I 720 mg), Na (1430 mg), S (1050 mg), Mg (555 mg), Zn (373 mg), (Mn 31.4 mg), Cu (8.4 ma), and P (269 mg). Toxic heavy metal contents were negligible. The fat@ acid content was (onpercent diy wt): 0.65% in 14:0;1.28% in 16:O; 1.48% in 1 6 : 1~7 ; 0.34% in 16:2&; 0.75% in 16:3& and 2.50% in 2 0 : 5~3 . Nutrient composition of biomass was highly influenced by means of the residence time in the culture bioreactor and the external irradiance. The biomass produced at low external irradiance was richer in protein and eicosapentaenoic acid. Journal of Food Biochemisby 25 (2001) 57-76. AN Rights Reserved. "Copyright by Food & Nutrition Press, Inc.. Trumbull, Connecticut 0661 1. 57 58 M.M. REBOLLOSO-FUENTES ETAL.

The polyunsaturated fatty acids (PUFA) eicosapentaenoic and arachidonic acids (EPA and AA), which have several pharmaceutical properties, have been purified from the red microalga Porphyridium cruentum. The process consists of only four main steps: (i) simultaneous extraction and saponification of the microalgal biomass; (ii) urea inclusion method (iii) PUFA esterification (iv) argentated silica gel column chromatography of the urea concentrate. Total AA and EPA recoveries reached 39.5% and 50.8% respectively for a purity approximately 97% for both fatty acids. Therefore, recovery of highly pure PUFA could be improved in organisms that are rich in two or more fatty acids of interest. The results of several procedures for AA and EPA recovery from several authors by using this microalga were compared.