(359f) Sequential Extraction of Triglycerides and Fucoxanthin with Supercritical Carbon Dioxide for the Valorization of the Integrated Biorefinery

The costs associated with producing renewable biofuels from algae have been prohibitive to their successful realization. However, pursuing an integrated biorefinery model through the valorization of additional high value and high purity products from algae can favorably shift the economics of the system. Of importance to realizing renewable fuels and chemicals sustainably, our work aligns with the Principles of Green Chemistry by replacing organic solvents, typically used for extraction from biomass, with nontoxic, green solvents like carbon dioxide (CO₂) through supercritical fluid extraction (SFE). In the supercritical phase, the solvation properties of CO₂, such as solvent polarity, hydrogen donating and accepting capacity, can be tuned by adjusting the temperature and pressure to enable the selective extraction of different biomass fractions. In this work, carotenoids (“super-antioxidants” like fucoxanthin) are selectively extracted from the microalgae Phaeodactylum tricornutum in a supercritical CO₂ flow through system to yield a solvent-free, high value enriched extract with commercial applications in pharmaceutical and nutraceutical products. We then examine a series of sequential, selective extractions targeting triacylglycerides or fucoxanthin and other carotenoids by systematically changing the supercritical solvent properties as well as the order of extractions targeting the different high value products. Solvent polarity were tuned by modulating pressure and volumes of ethanol co-solvent to achieve desired solvent properties, and the optimal order of extractions is determined to maximize product yields and purity. This work advances a greater initiative towards a large scale, algae-based bioeconomy via an environmentally benign, integrated biorefinery approach.