Supercritical CO2 extraction of γ-linolenic acid (GLA) from the cyanobacterium Arthrospira (Spirulina)maxima:: experiments and modeling

The freeze-dried biomass of Arthrospira was submitted to supercritical CO2 extraction, in a flow apparatus, at temperatures of 50 and 60 degreesC, pressures of 250 and 300 bar and flow-rates of 12.8, 19.6 and 29.5 9 CO2/min. The achieved extraction yields, using pure CO2, were low and increased slightly with pressure and temperature and decreased with the flow rate. In order to increase the extraction yield of the lipids, namely GLA, which is mostly contained in glycolipid fractions, a polar compound (ethanol) was mixed with the freeze-dried biomass. The presence of ethanol increased both lipid and GLA yields relatively to the extraction with pure CO2. A comparison between supercritical extraction and organic solvent extraction was also carried out, in what concerns lipid yields and fatty acid composition of total lipids. Furthermore, a plug flow model, in which the resistance to internal mass transfer is considered to be the controlling step, was applied to the supercritical CO2 extraction of lipids from the Arthrospira maxima. (C) 2004 Elsevier B.V. All rights reserved.