STRUCTURE AND CHEMISTRY OF A NEW CHEMICAL RACE OF BOTRYOCOCCUS-BRAUNII (CHLOROPHYCEAE) THAT PRODUCES LYCOPADIENE, A TETRATERPENOID HYDROCARBON

New strains of the hydrocarbon rich alga Botryococcus braunii Kützing were isolated from water samples collected in three tropical freshwater lakes. These strains synthesize lycopadiene, a tetraterpenoid metabolite, as their sole hydrocarbon. The morphological and ultrastructural characteristics of these algae are similar to those reported for previously described strains which produce either alkadienes or botryococcenes. The pyriform shaped cells are embedded in a colonial matrix formed by layers of closely appressed external walls: this dense matrix is impregnated by the hydrocarbon and some other lipids. We believe the new strains synthesizing lycopadiene form a third chemical race in B. braunii, besides the alkadiene and botryococcene races, rather than a different species. Like the other two types of hydrocarbons, lycopadiene was produced primarily during the exponential and linear growth phases. The major fatty acid in the three races was oleic acid. This fatty acid was predominant in the alkadiene race; palmitic and octacosenoic acid also were present in appreciable amounts in the three races. Cholest‐5‐en‐3β‐ol, 24‐methylcholest‐5‐en‐3β‐ol and 24‐ethylcho‐lest‐5‐en‐3β‐ol occurred in the three races; three unidentified sterols also were detected in the lycopadiene race. Moreover, the presence of very long chain alkenyl‐phenols in the lipids of algae of the alkadiene race was not observed in the botryococcene and lycopadiene races. Of the polysaccharides released in the medium, galactose appeared as a primary component: it predominated in the botryococcene race. The other major constituents were fucose for the alkadiene race and glucose and fucose for the lycopadiene race. Although morphologically similar, some important chemical differences exist among algae classified as B. braunii. Copyright © 1990, Wiley Blackwell. All rights reserved