Nature and hydrocarbon content of blooms of the alga Botryococcus braunii occuring in Australian freshwater lakes

Abstract

Under Australian conditions blooms of B. braunii were found to have hydrocarbon oil contents between 27 and 40% of the dry mass. The highest oil content was observed in a red bloom and the lowest in a green bloom of the organism. A number of branched-chain hydrocarbons of the general formula Cm H2n-10. where n equals 30. 34. 35. 36 and 37, have been found in both red and green blooms of the alga. Twelve of these hydrocarbons are novel to the present study and analysis by gas chromatography-mass spectrometry indicates that these compounds are closely related to or isomeric with botryococcene. Straight-chain hydrocarbons were present only in the green stage of the organism. Evidence for the simultaneous occurrence of branched- and linear-chain hydrocarbons in the same plant is inconclusive as blooms which revealed both types of hydrocarbons were known to contain both stages of the alga. The chemical parameters measured, both of the cell material and of the waters in which they grow, have thus far failed to explain why conditions are sometimes more favourable to the formation of B. braunii blooms than at other times. B. braunii has been observed to form shoreline deposits which undergo a change in pigmentation during desiccation to produce a black rubbery material bearing a strong resemblance to Coorongite. A detailed comparison has yet to be undertaken.