Microalgae are a promising alternative source of several bioactive compounds useful for human applications. However, lipids are traditionally extracted with toxic organic solvents (e.g. mixture of chloroform and methanol or hexane). In this work, we developed a new lipid extraction protocol to obtain a fatty acids rich extract from the diatom Phaeodactylum tricornutum. Deep Eutectic Solvents (DES) and microwaves (MW) were investigated as pre-treatments for environmentally friendly solvent extractions using dimethyl carbonate (DMC) and supercritical CO2 (scCO2). Pre-treatments with various DES formed by choline chloride (ChCl) and different hydrogen bond donors (oxalic acid, levulinic acid, urea, ethylene glycol and sorbitol) were tested in combination with DMC extraction. DES formed by ChCl and carboxylic acids gave best results, increasing both selectivity and total fatty acids (TFA) extraction yield of DMC (respectively by 16% and 80%). DES combined with MW heating followed by DMC extraction allows to reach comparable TFA yield and fatty acid profile to traditional Bligh & Dyer extraction method and much better selectivity (88% vs. 35%). This pre-treatment was also demonstrated to improve significantly extraction efficiency of scCO2, increasing by 20 times TFA yield and providing highly purified triglycerides extracts.

No abstract