Green extraction processing of lutein from Chlorella saccharophila in water-based ionic liquids as a sustainable innovation in algal biorefineries

Abstract

A billion tonnes of waste are generated every year in the food industry. Green extraction of natural antioxidants and therapeutics like carotenoids from microalgae using ionic liquids may help in improving the process efficiency and reducing the dependency on petroleum-based chemicals in the food industry. The extraction of carotenoids is solvent specific, and extraction efficiency varies greatly. The effect of 4 different ILs on carotenoid profiles of C. saccharophila was assessed and compared to a conventional solvent, methanol, to check their extractability. We found 40 % (w/v) Tetrabutyl phosphonium hydroxide as the best IL to extract the carotenoids. Tetrabutyl phosphonium hydroxide selectively extracts 2.26 mg g−1 dry cell weight (DCW) of lutein from wet biomass of C. saccharophila, whereas methanol extracts 0.10 mg g−1 DCW of lutein at room temperature-based extraction. Also, the combinatorial effect of temperature, extraction time, solvent: biomass ratio and ionic liquid concentration was investigated using a statistical modelling technique, Response Surface Modelling (RSM). It was found that lutein extraction is further improved by 10 % to 2.49 mg g−1 under the optimal extraction conditions [40 % (w/v) Ionic liquid concentration, 5 min extraction time, 0.5 (mL mg−1) Solvent: Biomass Ratio and 25 °C temperature]. Lutein remains 3 times more stable in IL than in conventional solvent methanol at 60 and 90 °C. Hence, Tetrabutyl phosphonium hydroxide can prospectively substitute conventional organic solvents in the downstream processing of bioactive compounds from microalgae.