Application of memberane dispersion for enhanced lipid milking from Botryococcus braunii FACHB 357

To improve the mixing efficiency in an aqueous–tetradecane system and thus to increase the lipid milking efficiency, poly (ether sulfones) hollow fiber membrane was applied as dispersion medium to establish an in situ lipid extraction process from Botryococcus braunii FACHB 357. The lipid location of this microalga was characterized by fluorescence microscope and transmission electron microscopy, respectively. The results showed that B. braunii excreted lipids into the outer matrix, which allowed it possible to extract algal lipids in situ by organic solvent. Within an aqueous–organic biphasic system, the lipid extraction ratio of tetradecane increased from 38.05% to 50.15% by introducing a microporous membrane as the dispersion medium, mainly because smaller solvent droplets were produced. Under this experimental condition (the volume ratio of tetradecane: 10%, the flow rate: 10 ml min−1), solvent toxicity and shearing stress had not shown significant impact on algal cells viability in 96 h. Within the same time period, the lipid amount extracted by solvent was enhanced with the increase of the solvent flow rate and the initial biomass concentration. These results suggested membrane dispersion was a good choice to improve mixing effect in the algal lipid milking process or other similar cell products extracted processes.

► An in situ algal lipid extraction process was established for lipids recovery from Botryococcus braunii FACHB 357 by the biocompatible tetradecane solvent.
► Hollow fiber micro-filtration membrane was used as dispersion medium to enhance the mixing efficiency and the algal lipid extractability in a biphasic system.
► 92% of algal cells were found still viable within the aqueous–tetradecane system after 96 h treatment.