*3.2. Supercritical Fluid Extraction*

Supercritical CO2 with ethanol as a co-solvent can be used to extract MPLs effectively, yielding purities of 26.26% and 16.88% from WPPC and BMP extractions, respectively (Figure 3a). The SFE operation can be conducted at 50–60 ◦C [95] and 350–550 bar [49]. The SFE co-solvent (CO2 and 20% ethanol) allowed for complete extraction of PE, PC, and SM. However, neither PS (i.e., the vital compounds for cognitive function) nor PI were extracted [61,96]. Therefore, the co-solvent method may be an invalid industrial process due to the incompleteness of PS/PI recovery. In addition to co-solvents, dimethyl ether near the critical point (DME, 20%–30% solubility, 333 K, 40 bar) and supercritical CO2 are able to dissolve polar and neutral lipids, respectively [59].

Supercritical fluid DME has been used to extract polar lipids, resulting in a yield of 69.1–77.8%. The SFE process shown in Figure 3b can accept both liquid and powder inputs [59,97]. This unit can work with CO2 and DME in two-stages, extracting neutral and polar lipids, separately. In addition to a two-step operation, this unit can also operate a single extraction with DME. Near-critical DME dissolves both polar and non-polar lipids in the SFE chamber. Through a two-stage de-pressurization, lipids are separated from the protein fraction, whereas vaporized DME is compressed and condensed for reuse (Figure 3b). This method features properties such as non-toxicity, a compact skid, feeding

flexibility, and a high content of MPLs (65.7–75.5 g MPLs per 100 g DM). However, the MPL recovery rate (69.1–77.8%) needs further improvement.
