Microalgae grow in diverse environments and possess a great biotechnological potential as
they contain useful bioactive compounds. These bioactive compounds can be obtained by selective
and energy-efficient extraction methods. Various industries are using the supercritical fluid extraction
(SFE) method to extract these valuable bioactive compounds. Hence, for the first time, we evaluated
the effects of SFE on the recovery of bioactive and antioxidant compounds using Coccomyxa onubensis,
a eukaryotic acidophilic microalga of potential relevance which can be used in the field of nutraceutical
and functional foods. It was isolated from the Tinto River (Pyritic Belt, Huelva, Spain), a mining
region in Spain. Variables such as extraction yield, lutein purity (LP) and recovery (LR), total phenols,
and antioxidant capacity (Trolox equivalents antioxidant capacity method) were studied using a
Box–Behnken design based on a response surface methodology along with the overall extraction
curve fitted to a spline linear model. The effects of temperature (30, 50, and 70 C), pressure (25, 40,
and 55 MPa), and the percentage of co-solvent (0, 25%, and 50% v/v ethanol) on SFE were analyzed,
resulting in the co-solvent and temperature as the most significant factors followed by the pressure.
Under 70 C, 40 MPa, and 50% v/v ethanol, C. onubensis reached a maximum of 66.98% of LR.
The extracts were richest in total phenols and showed the maximum antioxidant activity (36.08 mg
GAEs/g extracts and 2.237 mmol TE/g extracts, respectively) under similar pressure and co-solvent
percentage values and different temperatures (30 and 70 C, respectively). The extracts obtained in
this study may have potential applications in the food, nutraceutical, and cosmetic industries. SFE is
a highly efficient method to valorize microorganisms living in extreme environments, which are so
far unexplored using green extraction methods
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