Supercritical CO2 Extraction of High-Added Value Compounds from Chlorella vulgaris: Experimental Design, Modelling and Optimization

Microalgae are well-known for their high-added value compounds and their recovery is currently of great interest. The aim of this work is the recovery of such components from Chlorella vulgaris through supercritical fluid extraction (SFE) with CO2. The effect of the extraction temperature (40-60 degrees C), pressure (110-250 bar), and solvent flow rate (20-40 g/min) was tested on yield, the extract's antioxidant activity, and the phenolic, chlorophyll and carotenoid content. Thus, data analysis indicated that the yield was mainly affected by temperature, carotenoids by pressure, while the extract's phenolics and antioxidant activity were affected by the synergy of temperature and pressure. Moreover, SFE's kinetic study was performed and experimental data were correlated using Sovova's mass transfer-based model. SFE optimization (60 degrees C, 250 bar, 40 g/min) led to 3.37% w/w yield, 44.35 mg(extr)/mg(DPPH) antioxidant activity (IC50), 18.29 mg(GA)/g(extr) total phenolic content, 35.55, 21.14 and 10.00 mg/g(extr) total chlorophyll, carotenoid and selected carotenoid content (astaxanthin, lutein and beta-carotene), respectively. A comparison of SFE with conventional aq. ethanol (90% v/v) extraction proved SFE's superiority regarding extraction duration, carotenoids, antioxidant activity and organoleptic characteristics of color and odor despite the lower yield. Finally, cosolvent addition (ethanol 10% w/w) at optimum SFE conditions improved the extract's antioxidant activity (19.46%) as well as yield (101.81%).

Automated summary

This study aimed to recover high-added value compounds from Chlorella vulgaris through supercritical fluid extraction (SFE) with CO2. The effects of extraction temperature, pressure, and solvent flow rate on yield, antioxidant activity, and content of phenolics, chlorophyll, and carotenoids were investigated. SFE optimization led to improved antioxidant activity and yield compared to conventional ethanol extraction, despite the lower yield. The addition of a co-solvent further enhanced both the antioxidant activity and yield of the extract.