Supercritical carbon dioxide treatment of the microalgae Nannochloropsis oculata for the production of fatty acid methyl esters

• Extraction of fatty acid methyl esters from Nannochloropsis oculata using supercritical fluids at low temperatures and pressures.
• Using methanol as a co-solvent, extraction and transesterification was achieved in a single step.
• Long chain FAMEs such as EPA and DHA were produced using methanol as a co-solvent.
• Using hexane as a co-solvent, higher amounts of fatty acid methyl esters were obtained using 5.9 MPa than at 7.6 MPa.

The aim of this work was to evaluate the potential of supercritical carbon dioxide (CO2) to extract fatty acid methyl esters (FAME) from the microalgae Nannochloropsis oculata (N. oculata) at low temperatures (37 and 55 °C) and pressures (5.9 and 7.6 megapascals (MPa)). A qualitative gas chromatography (GC) analysis showed that the individual FAMEs extracted varied depending on the co-solvent (methanol or hexane) used with supercritical CO2. Using hexane, FAME compounds produced were similar to those extracted with soxhlet extraction alone while longer chain FAME were produced when methanol was the co-solvent. The effects of pressure and temperature variations were shown to be of statistical significance. The chromatograms produced in this work demonstrate that altering one of these parameters (co-solvent, temperature, pressure) can produce different compounds owing to the tunability of the technique.

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