(105d) Elucidating the Extraction of Fucoxanthin from Algae with Supercritical Carbon Dioxide and Ethanol as a Cosolvent for the Valorization of the Integrated Biorefinery

Integrated biorefineries that produce a variety of chemicals, fuels, and products from renewable biomass sources are key in the move towards a sustainable future not dependent on fossil fuels. The integrated biorefinery’s success is tied to its economic viability, creating high-value products along with lower-value biofuels. This work examines the extraction of high-value nutraceuticals from algae biomass as a way to economically enable the integrated biorefinery using green chemistry approaches. Green solvents, such as supercritical carbon dioxide and pressurized carbon dioxide with ethanol as a cosolvent, are deployed to extract high-value nutraceuticals such as fucoxanthin from the algae biomass, Phaeodactylum tricornutum. There has been growing interest in fucoxanthin as a nutraceutical from algae sources, but experimental studies do not agree on an optimized condition for maximum fucoxanthin recovery in extractions with supercritical carbon dioxide or pressurized carbon dioxide with ethanol as a cosolvent. This work analyzes the proposed optimal conditions for fucoxanthin extraction in current literature and statistical trends are examined for variables that increase fucoxanthin yield. Statistical analysis indicates that higher polarity achieved by either higher operating pressures in supercritical carbon dioxide or the addition of ethanol as a co-solvent correlates with higher yields of fucoxanthin, but it is difficult to untangle the effect of the algae (as many different species of algae are used, both macro- and microalgae) and other variables from these studies. Here, the solubility of fucoxanthin in supercritical carbon dioxide and the role of ethanol as a co-solvent in extracting fucoxanthin is fully investigated through extractions on pure fucoxanthin standard, which are fit using the Chrastil model of solubility in supercritical carbon dioxide. These experiments are then compared with extractions on the microalgae, Phaeodactylum tricornutum, to elucidate the effect of the algae matrix on fucoxanthin recovery. In microalgae extractions, a significant finding was that in mildly-polar high pressure (50 MPa) supercritical carbon dioxide extractions, there was evidence of selectivity of the desired product, fucoxanthin, over the undesired polar pigment co-product, chlorophyll. This selectivity was not seen in more polar extractions with ethanol, indicating an additional benefit of using supercritical carbon dioxide solvent. This study aims to impart a greater understanding of the extraction of the high-value nutraceutical, fucoxanthin, in order to enable the integrated biorefinery.