Comparison of alternative solvents for in situ extraction of hydrocarbons from the colonial green alga Botryococcus braunii race B (Showa)

The colony-forming, green microalga Botryococcus braunii secretes petroleum-like hydrocarbons, which enables the non-destructive continuous in situ extraction, ‘milking’, of these extracellular products during culture growth without cell lysis. This work compares the suitability of 15 different solvents, including alkanes, halogenated solvents, and green solvents, for in situ extraction of B. braunii race B (Showa strain) hydrocarbons after acclimation to moderate salinity stress. After 24 h of extraction, bio-based terpene ‘green’ solvents such as ɣ-terpinene showed the highest hydrocarbon recovery, around 10-fold greater than with conventional alkane solvents. Brominated alkanes and liquid perfluorocarbons (FCs) formed a lower phase to algal cultures rather than an upper phase as with other solvents, but only bromodecane effectively captured extracellular hydrocarbons similar to conventional alkane solvents. However, bromodecane and all green solvents were too toxic for two-phase continuous culture contact hydrocarbon milking, leading to 33–100% chlorophyll content loss. To overcome the biologically adverse effects of these solvents with suitable hydrocarbon recovery, future research should focus on their application in short-term extraction period ‘milking’ systems to minimize algal-solvent contact and enable continuous extraction. ![Graphical Abstract][1] Graphical Abstract ### Competing Interest Statement The authors have declared no competing interest. [1]: pending:yes