Lipid extraction from microalgae covered with biomineralized cell walls using liquefied dimethyl ether

Cell disruption is regarded as an indispensable pretreatment step before the extraction of microalgae with biomineralized cell walls. Here, two typical microalgae-diatom Chaetoceros gracilis (C. gracilis) and coccolithophore Pleurochrysis carterae (P. carterae)-covered by hard biomineralized cell walls were used as starting materials for lipid extraction using liquefied dimethyl ether (DME) without any pretreatment such as drying or cell disruption. The liquefied DME extraction experiments were performed at 25 degrees C and 0.59 MPa using a semi-continuous, flow-type system. The results of the yield, elemental composition, molecular weight distribution, fatty acid composition, and trace element composition indicated that the performance of liquefied DME extraction was similar to that of Bligh-Dyer extraction and better than that of hexane Soxhlet extraction, despite the latter two methods requiring pre-drying and cell disruption processes. It was also proven that the cell wall of microalgae would not affect lipid extraction of liquefied DME, thereby the liquefied DME extraction method is suitable for extracting lipids from microalgae with biomineralized cell walls. Besides, the lipids extracted by liquefied DME can be further used for biodiesel production.