Supercritical CO2 extraction of Aurantiochytrium sp. biomass for the enhanced recovery of omega-3 fatty acids and phenolic compounds

Acknowledgements : This work was funded by the project “Valorização dos subprodutos do processo biotecnológico de produção de esqualeno e DHA pela microalga Aurantiochytrium sp.” (AlgaValue) (ref. 17680), and within the scope of the project CICECO Aveiro Institute of Materials, UIDB/50011/2020 & UIDP/50011/2020, and strategic program of MARE (MARE-UID/MAR/04292/2013), financed by national funds through the FCT/MCTES. Authors also thank the funding from Project AgroForWealth (CENTRO-01-0145-FEDER- 000001), funded by Centro2020, through FEDER and PT2020 and University of Aveiro and FCT/MCT for the financial support for the QOPNA research Unit (FCT UID/QUI/00062/2019) through national founds and, where applicable, co-financed by the FEDER, within the PT2020 Partnership Agreement. The project was also partially funded by the Integrated Programme of SR&TD “SmartBioR” (reference Centro-01-0145-FEDER-000018) cofunded by Centro 2020 program, Portugal2020, European Union, through the European Regional Development Fund.

The microalgae Aurantiochytrium sp. is a strong alternative source of ω-3 fatty acids, including ocosahexaenoic acid (DHA). This work encompasses the optimization of SFE conditions to maximize the total extraction yield (ηTotal), DHA content (CDHA), total phenolics content (TPC), and antioxidant capacity (AOC) of the extracts produced from Aurantiochytrium sp. biomass. A full factorial experimental plan was performed, comprising three factors (pressure, temperature, and flow rate) and two levels (200−300 bar, 40−80 °C, and 6–12 gmin−1, respectively). The maximum and minimum experimental results were ηTotal = 2.1 and 13.4 wt.%, CDHA= 27.3 and 39.3 wt.%, TPC =1.19 and 2.24 mgGAE g−extract 1 , and AOC = 0.3 and 1.4 mg g− TEAC extract 1. Under the studied experimental conditions, increasing pressure up to 300 bar is the optimum to rise both ηTotal and CDHA. Temperature increase from 40 to 80 °C leads to opposing effects: it favors the concentration of phenolics in the supercritical extracts at the expenses of decreasing DHA content and total yield. Surface models were adjusted to ηTotal, CDHA and TPC data, and the goodness of the fits ranged from coefficients of determination of 0.752-0.711 (TPC) to 0.997-0.994 (CDHA). Under optimized conditions, supercritical extracts exhibited a DHA content more than 3.5-fold richer than fish oil, and 7.9-fold richer than the best alternative microalgae species (Pavlova lutheri) found in the literature.

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