Microalgal carotenoid recovery in a biorefinery approach

Introduction Microalgae culture to be effective as feedstock for bio-energy production needs to overcome constraining biotechnological, technological and economic factors [1]. In order to establish an economically viable process, the co-production of renewable fuels along with bioproducts (for pharmaceutical, food, feed, chemicals industry, etc.), in a biorefinery concept has been considered [2]. In this concern the deal of the SunCHem project is to produce methane from the catalytic hydrothermal gasification of microalgal biomass and to recover high-value products. In this sense the Laboratory for Environmental Biotechnology at EPFL is developing research to achieve higher biomass production and yield of bio-products such as PUFA-3 and carotenoid pigments. The present work investigated the effects of different conditions of pressurized liquid extraction for obtaining carotenoids from Scenedesmus vacuolatus and Chlorella vulgaris. Experimental Pigments were extracted from lyophilized biomass (0.3 g) of Scenedesmus vacuolatus (SAG 211 - 8B) and Chlorella vulgaris (CCAP 211/12) by pressurized liquid extraction using Dionex ASE200 (Sunnyvale, CA, USA) at 1500 PSI, 130oC, assessing the time of static phase (3 cycles of 7 min or 3 cycles of 13 min) and the solvent concentration (ethanol 70 or 96%), following a factorial plan 22. The samples, saponified and non-saponified, were analyzed by HPLC system consisting of a Spherisorb ODS-2 C18 5 m PEEK guard column connected to a Vydac 201TP54 (250 x 4.6 mm) reverse phase C18 column. The samples were eluted using isocratic mobile phase composed of acetonitrile/methanol/dichloromethane (75:20:5, v/v/v) containing 10 mmol/L ammonium acetate, 4.5 mmol/L butylated hydroxytoluene and 3.6 mmol/L triethylamine at a flow rate of 1.5 ml/min. All carotenoids were detected at 450 nm and compared with carotenoid standards. Results and Discussion As preliminary results, lutein appeared to be the principal pigment present among the carotenoids evaluated in both S. vacuolatus and C. vulgaris extracts. Lutein was recovered more efficiently at 70% ethanol and 3 cycles of 3 min conditions, achieving 8.5 mg g-1 and 29.5 mg g-1 for S. vacuolatus and C. vulgaris respectively. Between the species studied, C. vulgaris extract thus showed the highest lutein concentration. Lutein is the second in the ranking of the global carotenoids market and as antioxidant has a potential role in preventing or ameliorating age-related macular degeneration [3]. Pressurized liquid extraction can be considered as an environmental clean extraction method [4], and by using solvents allowed for the food and pharmacy industries, it may be a powerful tool for pigments recovery as a pre-step of the catalytic hydrothermal gasification proposed in the SunCHem project. Conclusions Pressurized liquid extraction was efficient for the extraction of pigments from microalgal biomass, and the best condition was 70% ethanol and 3 cycles of 3 min for both species. Lutein was the principal pigment recovered. More in deep investigation are being performed to evaluate the viability of the whole process and to go forward into the development of this biorefinery concept.