Extraction of astaxantine and phycocyanine from microalgae with supercritical carbon dioxide

Astaxantine from the microalga Haematococcus pluvialis and phycocyanine from the microalga Spirulina maxima have been obtained by supercritical extraction using carbon dioxide. Prior to extraction, the samples of microalgae were crushed by cutting mills (coffee mill) and then manually ground with dry ice (solid carbon dioxide). The Haematococcus extracts were analyzed by liquid chromatography, using astaxantin (purity of 98%) as a standard. Phycocyanine, being insoluble in carbon dioxide, was indirectly separated. Thus, lipid-soluble substances from spirulina were extracted and analyzed by liquid chromatography, using as a standard a solution prepared on the base of reagent (purity of 40%). For the astaxantine extraction, the results show that cellular wall breaking has an important effect on extraction efficiency. The addition of a cosolvent (9.4 mass % of ethanol) has little effect, reaching an extraction yield of about 1.7 mass %. The extraction yield is much below the expected lipid content in dry Haematococcus alga samples, which is known to be close to 30 mass %. The maximum total recovery of astaxantin, calculated from its initial and residual content in the alga (0.0147 and 0.0004, respectively), exceeds 97%. For phycocyanine extraction, the addition of cosolvent (10 mass % of ethanol) has a strong effect on the extraction yield of lipidic substances. This value goes from about 1.1% for extraction without cosolvent to about 1.7 mass % when the cosolvent is used. The total extraction yield of about 3 mass % corresponds well to the average lipid content of 3.27% in alga Spirulina maxima reported in the literature.