Supercritical fluid extraction and pressurized liquid extraction processes applied to eicosapentaenoic acid-rich polar lipid recovery from the microalga Nannochloropsis sp

Abstract

This work studies the simultaneous extraction and fractionation of saponifiable lipids into neutral saponifiable lipids and polar lipids (phospholipids and glycolipids) from the microalga Nannochloropsis sp. (41.9% neutral saponifiable lipids, 58.1% polar lipids, 32.5% eicosapentaenoic acid, EPA) to obtain EPA-rich polar lipid fractions, using green techniques. Several two-step extraction processes were studied, combining CO2 supercritical fluid extraction, pressurized lipid extraction, and ethanol-gas (CO2) expanded extraction. Extraction at atmospheric pressure, including the Soxhlet extraction method, was used as the reference. Firstly, a lipidic fraction rich in neutral saponifiable lipids (80.4% of total saponifiable lipids), was obtained using hexane and the Soxhlet extraction method; this extract contained 85.8% of the biomass neutral saponifiable lipids. Subsequently, in the second extraction step using ethanol, an EPA-rich polar lipid extract with 89.2% polar lipids and up to 39.6% EPA was obtained. This SL extract contained 80.1% of the glycolipids, 96% of the phospholipids and 67.8% of the EPA from the Nannochloropsis sp. biomass. Good results were obtained combining the CO2 supercritical fluid extraction and pressurized lipid extraction techniques as alternative green processes. Firstly, a lipidic fraction rich in neutral saponifiable lipids (70.3% of the total extracted saponifiable lipids) was obtained using supercritical CO2 with 10 wt% ethanol as the co-solvent, at 35 MPa, 50 °C, 8 g CO2/min for 8 h; this extract contained 81.7% of the biomass neutral saponifiable lipids. Then, in the second extraction step with pressurized ethanol, at 10 MPa, 125 °C and three extraction cycles of 5 min, an EPA-rich polar lipid extract with 85.1% polar lipids and up to 39.2% EPA was obtained. This saponifiable lipid extract contained 76.9% of the glycolipids, 71.1% of the phospholipids and 61.9% of the EPA from the Nannochloropsis sp. biomass.