Growth and hydrocarbon production of microalga Botryococcus braunii in bubble column photobioreactors.

Microalga Botryococcus braunii, which produces high levels of liquid hydrocarbons called botryococcenes, was cultivated in bubble column photobioreactors. Algal cells, adapted to low irradiance (3 klx) in the preculture, showed lower biomass and hydrocarbons productivity in the photobioreactor illuminated at high irradiance (10 klx) due to the effects of photoinhibition. The degree of photoinhibition was reduced by partial shading, the lighted volume ratio being varied from 25 to 100%. The algal cells adapted to high irradiance in the preculture showed a high biomass productivity at 10 klx: the cell concentration reached higher than 7 kg/m3 and the hydrocarbon content was 50% based on cell dry weight. Hydrocarbon production kinetics of this alga in the linear growth phase was found to be growth-associated irrespective of the experimental conditions of illumination and preculture.