Extraction of oil and carotenoids from pelletized microalgae using supercritical carbon dioxide

• The experiments were designed with response surface methodology.
• High temperature and CO2 density allow high recovery of oil and carotenoids.
• The highest recovery of oil and carotenoids was achieved at 64 °C and 956 kg/m3.
• The lipids extraction yield from pelletized microalga was higher than from non-pelletized microalga.
• Microalgal supercritical extract showed important antioxidant and anti-inflammatory properties.

Nannochloropsis gaditana is a microalga characterized by its high content of lipids and as an important source of carotenoids, which are recognized to be potent natural antioxidants. A central composite design using response surface methodology was used to study the effects of temperature (36–64 °C) and CO2 density (914–956 kg/m3, in a pressure range between 31.7 and 54.3 MPa) on the recovery of oil and carotenoids from pelletized N. gaditana by supercritical CO2. Extraction yields of oil and carotenoids varied between 110.1 and 152.9 g/kg dry substrate and between 393.0 and 773.7 mg/kg.d.s., respectively. The recovery of oil and carotenoids increased with the temperature and CO2 density, reaching the highest recovery at 64 °C and 956 kg/m3 (59.3 MPa). Temperature had a greater effect on response variables than CO2 density. Antioxidant activity (DPPH assay and bleaching β-carotene assay) and anti-inflammatory activity (lipoxygenase inhibition) were measured in selected supercritical extract, and important antioxidant properties were demonstrated.

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