Microalgal lipids and carotenoids: can we extract them in an eco-friendly way?

Microalgae are crucial for meeting the global population's needs regarding more sustainable food supplies, explicitly concerning the demand for lipids and other lipophilic compounds, like carotenoids. However, the extraction process to recover them faces environmental concerns associated with conventional petrochemical-based extraction methods. In this talk, I will introduce our novel advancements in eco-friendly approaches using enzyme-based methods and ultrasound systems in combination with green solvents to extract lipids and carotenoids from different microalgal species of interest (Microchloropsis gaditana, Tisochrysis lutea, Porphyridium cruentum, and Phaeodactylum tricornutum), followed by advanced identification methods. For microalgal lipids, promising approaches using ultrasonic-assisted enzymatic extraction methods were developed, achieving yields comparable to the conventional Folch method. Similar n-3 content was found by GC-MS regardless of the method used (55%, 42%, 31%, and 21% for T. lutea, M. gaditana, P. tricornutum, and P. cruentum, respectively), showing that the green approaches did not affect the fatty acid profile. In terms of carotenoids, an innovative ultrasonic probe system was developed to significantly enhance their recovery, concurrently reducing the extraction time (5 min vs. 24 h of the conventional method) and employing a sustainable solvent, such as ethanol. This advancement improves yield and contributes to the extraction process's overall sustainability, as evaluated by AGREEprep™ software. Additionally, the study demonstrated the potential for biomass valorization through a cascading approach to microalgal residues obtained after lipid extraction. Carotenoid recovery rates were notably high (41%, 60%, 61%, and 100% for M. gaditana, P. tricornutum, T. lutea, and P. cruentum, respectively) compared to the original biomass. Furthermore, this research provided new insights into carotenoid profiles using HPLC‑DAD and HRMS. In conclusion, this multidisciplinary approach sheds light on the green production of lipids and carotenoids from microalgae, presenting novel eco-friendly approaches for producing high-value compounds with significant potential as ingredients for functional foods and nutraceuticals.