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

• Published in: Algal research (Amsterdam) 2022-01, Vol.61, p.102586, Article 102586
• Main Authors: Jiménez Callejón, María J., Robles Medina, Alfonso, Macías Sánchez, María D., González Moreno, Pedro A., Navarro López, Elvira, Esteban Cerdán, Luis, Molina Grima, Emilio
• Format: Article
• Language: English
• Subjects: Eicosapentaenoic acid (EPA); Microalga; Polar lipid; Pressurized liquid extraction (PLE); Supercritical fluid extraction (SFE)
• ISSN: 2211-9264; 2211-9264
• DOI: 10.1016/j.algal.2021.102586

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. •Microalgal saponifiable lipids (SLs) were extracted and fractionated by non-toxic solvents.•Polar lipids rich in EPA were obtained by supercritical and pressurized extraction.•SLs with 70% neutral lipids were extracted with supercritical CO2 in a first step.•85% polar lipids (39% EPA) were extracted with pressurized ethanol in a second step.•Up to 75% of the glycolipids and phospholipids were recovered in polar lipid extracts.