Permeabilization of Chlorella sorokiniana and extraction of lutein by distillable CO₂-based alkyl carbamate ionic liquids

Chlorella sorokiniana is an alternative microalgal source of lutein, which is a type of phytonutrient with various health benefits. Different solvent extraction strategies have been explored for the recovery of carotenoids from microalgae. In particular, the conventional imidazolium- and pyridinium-based ionic liquids (ILs) are attractive due to their ability to permeabilize the microalgae. However, the challenges remain in separating the extracted carotenoid from ILs solvent. To overcome this shortcoming, CO₂-based alkyl carbamate ILs were proposed as an alternative solvent that can function as a cell permeabilizing agent and an extraction solvent for recovery of lutein from Chlorella sorokiniana. A complete separation of lutein from the ILs was achievable by distillation of ILs under mild conditions. In an optimized extraction system conducted at room temperature for 45 min, a co-solvent system made of dipropylammonium dipropylcarbamate (DPCARB, 80% v/v) and methanol yielded 971.18 ± 17.88 mg/g lutein. The recyclability of DPCARB was tested and the results showed that the extraction performance of the recycled IL was satisfactory after three cycles of extraction. CO₂-based alkyl carbamate ILs hold a good potential in the extraction of lutein due to their recyclability that mitigates environmental impact and reduces operating cost.