BIOCHEMICAL-COMPOSITION OF MICROALGAE FROM THE GREEN ALGAL CLASSES CHLOROPHYCEAE AND PRASINOPHYCEAE .1. AMINO-ACIDS, SUGARS AND PIGMENTS

The biochemical composition of 10 species of green microalgae was determined. The species examined included 3 marine chlorophytes (Chlorella sp. (CS-247), Chlorella sp. (CS-195) and Stichococcus sp.), and 6 marine prasinophytes (Pyramimonas cordata, Tetraselmis chui, a temperate and a tropical strain of Micromonas pusilla, Pycnococcus provasolii, and one unidentified coccoid prasinophyte (CS-126)). Pigment composition (e.g. presence of the chlorophyll c-like pigment Mg 2,4 divinyl pheoporphyrin a5 monomethyl ester (Mg 2,4 D); and lutein, prasinoxanthin or siphonaxanthin-like carotenoids) assisted in the taxonomy of the new strains. One freshwater chlorophyte (Chlorella protothecoides) was included for comparison. The protein content of all species ranged from 15.2-25.6% of dry weight except for the tropical M. pusilla (5.5%), and carbohydrate ranged from 10.8-16.7% for all species except Chlorella sp. (CS-195) (5.9%). Total lipid varied from 8.5-18.4% of dry weight among the species; chlorophyll a from 0.23-1.54% of dry weight. Amino acid profiles showed only minor variations between species, with the exception of tryptophan and arginine. Two species, Chlorella protothecoides and Chlorella sp. (CS-195) had lower proportions of tryptophan (< 0.5% of total amino acids) compared to the other species (1.0-1.8%) while arginine showed large variations across all species ranging from 4.7% (tropical M. pusilla) to 15.0% (T. chui). Glucose was the dominant sugar in the polysaccharide fraction of eight of the species. Galactose was the major sugar in the unidentified prasinophyte (CS-126) accounting for 54% of sugars. A wide range of sugars was found in Chlorella sp. (CS-195) with glucose making up only 19.3%. The possible use of the species in mariculture, based on their biochemical composition, is also discussed.