Supercritical CO2 extraction of γ-linolenic acid (GLA) from Spirulina platensis ARM 740 using response surface methodology

Spirulina platensis, a blue-green algae, is a potential source of the nutraceutical, γ-linolenic acid (GLA). The present work reports on recovery of GLA from S. platensis ARM 740 by supercritical carbon dioxide extraction (SCE) in comparison with conventional solvent extraction. Response Surface Methodology (RSM) was applied to optimize the operating conditions for high recovery of GLA by SCE. The levels studied were a pressure range between 100 and 500 bars, a time period between 26 min and 94 min and an ethanol level of 9.64–16.4 ml ethanol/16 g of freeze-dried biomass. The use of ethanol as a co-solvent with CO2 considerably increased the GLA yields compared to SCE. A recovery of 102% GLA in the supercritical extract (as compared to Bligh and Dyer extraction) was obtained in 1 h using a minimum of 13.7 ml of ethanol as co-solvent per 16 g of biomass, a temperature of 40 °C and a pressure of 400 bars. Supercritical CO2 with a co-solvent is therefore recommended as a better option to the conventional solvents for the complete recovery of GLA from S. platensis.