Extraction of β-carotene and lipids from wet biomass of the oleaginous yeast Rhodosporidium toruloides with supercritical CO2

The present study investigated supercritical CO₂ extraction (SCE) of β-carotene and lipids from wet biomass of the oleaginous yeast Rhodosporidium toruloides to assess its potential as a green and energy-effective extraction process. The influence of the water content of the biomass on the extraction kinetics was investigated by performing SCE with biomass with different water contents (80.3 wt%, 40 wt%, and 3 wt%). The CO₂ flowrate was set to 0.240 g s⁻¹. Despite an initial delay in the extraction process, the extraction yields from wet and dried biomass after 195 min (50 °C and 250 bar) showed no significant difference, confirming that an energy-intensive drying step before extraction can be avoided. The effects of temperature (40 °C - 70 °C) and pressure (200 bar - 400 bar) on extraction kinetics were systematically studied. Ethanol as a co-solvent significantly improved extraction efficiency, increasing β-carotene yield (up to 77 %) and lipid yield (up to 49 %). Yeast intracellular lipids were proven to act as an effective natural co-solvent for β-carotene extraction, as evidenced by the significant improvement in β-carotene recovery by 63 % when 10 wt% sunflower oil was added to the wet biomass as a co-solvent. The fatty acid methyl esters (FAME) analyses showed that the extraction conditions did not influence the FAME composition. The obtained extracts exhibited notable antioxidant activity, with an IC₅₀ of approximately 2 mg mL⁻¹, highlighting the potential of the oleaginous yeast Rhodosporidium toruloides as a valuable source for applications in functional foods and pharmaceutical products.