Ultrasound-assisted extraction of carotenoids from phytoene-accumulating Chlorella sorokiniana microalgae: Effect of milling and performance of the green biosolvents 2-methyltetrahydrofuran and ethyl lactate

This study aimed at optimizing the accumulation of phytoene in Chlorella sorokiniana by using norflurazon and investigating the capacity of green and traditional solvents to extract carotenoids by ultrasound-assisted extraction with and without previous milling. Phytoene-rich first described C. sorokiniana biomass was used, both fresh, freeze-dried, and encapsulated. The ideal dose of norflurazon (1 µg/mL) was selected to block the carotenoid pathway at the level of phytoene desaturase and induce the accumulation of phytoene in C. sorokiniana. A mill pre-treatment allowed a higher recovery of carotenoids compared to non-milled samples, in both the freeze-dried and encapsulated matrices. 2-Methyloxolane provided a higher total carotenoid content (4.75-5546.96 µg/g) compared to the other solvents tested in all the matrices, proving a promising bio-based solvent to replace traditional organic ones for the extraction of microalgal carotenoids.