Mechanical cell disruption of microalgae for investigating the effects of degree of disruption on hydrocarbon extraction

The colonial microalga, Botryococcus braunii, produces and stores hydrocarbons in membranes and in colonies. Although hydrocarbons in B. braunii could easily be extracted for biofuel production, yields are actually poor without energy-intensive pretreatment such as thermal drying. To develop extraction methods without drying, we applied the mechanical cell disruption to wet B. braunii using either a high-pressure homogenizer, a bead mill, or a circulating particle disruptor (Jet-Paster) and examined the relationships between the extent of cell and/or colony disruption and extracted hydrocarbon yields using n-hexane. When the number of particles over 20 μm classified as colonies, decreased after each treatment, the hydrocarbon yields of samples treated (over 20%) were much larger than those without treatments (under 5%). Thus, the colony disruption may increase hydrocarbon yields by enhancing n-hexane penetration to the colony. Although the degree of disruption on the Jet-Paster treatment was the lowest (2.2–9.3%) and that of sample treated by the homogenizer was the highest (27–55%), extracted hydrocarbon yields were improved in both treatments. The facts indicate that disrupting large colonies into small colonies improves hydrocarbon recovery, and the fractionation of cells is not needed for hydrocarbon extraction from B. braunii.