High-yield cultivation of Botryococcus braunii for biomass and hydrocarbons

Abstract

Botryococcus braunii is one of the most promising energy microalgae with a high content of hydrocarbons. Photoautotrophic cultivation is essential while the productivity is lowered by the long period of preparation for seeds. Therefore, a new strategy of photoautotrophic culture with heterotrophic seeds was proposed. The pH-auxostat fed-batch heterotrophic cultivation was developed, by which the biomass reached 37.02 g L−1 at 28 day in the 5 L fermenter. The effects of inoculum with heterotrophic seeds into photoautotrophic cultivation were verified. By this strategy, the final content and productivity of hydrocarbon was 35.9% and 128.3 mg L−1 d−1 respectively in 1 L bubble column photo-bioreactors indoors, the highest ever reported. Furthermore, the heterotrophic seeds were successfully applied to photoautotrophic cultivation in 3 L flat panel photo-bioreactors and 120 L open circle ponds outdoors, in which the final content and productivity of hydrocarbon were 27.85% and 35.06 mg L−1 d−1, indicating an efficient and feasible approach for producing biofuel from B. braunii.