Microalgae as green factories of lipids: insights from lipidomic analysis and bioactivity testing

Abstract: The demand for sustainable and eco-friendly food ingredients has experienced an outstanding increase in recent years. Microalgae are crucial sources for meeting population needs in terms of valuable lipids, including omega-3 and omega-6 long chain-polyunsaturated fatty acids (n-3 and n-6 LC-PUFA) and more complex lipids such as glycolipids and phospholipids. However, the environmentally-friendly extraction of these bioactive remains unexplored. In this work, the use of enzyme-based methods in combination with ultrasounds was evaluated as green approaches to produce high-quality lipid extracts. Moreover, the effect of eco-friendly approaches on the lipidome profiles and the bioactivity of microalgal lipids were also investigated to evaluate the potential of these valuable lipids in health and food applications. A novel lipidomics workflow was applied for the analysis of the microalgae lipidome based on liquid chromatography high-resolution mass spectrometry (LC-HRMS). Different lipids containing n-3 and n-6 LC-PUFA of nutritional importance were identified, including neutral and polar lipids, such as phosphatidylcholines (PC), triglycerides (TG), as well as galactolipids including monogalactosyldiacylglycerols (MGDG), and digalactosyldiacylglycerols (DGDG). The lipid composition differed from the extraction methods applied depending on the enzymatic solution used, leading to enriching the extracts with different lipid classes. In terms of bioactivity, the cytotoxicity of the produced lipids was assessed by comparing human colon cancer cells (HCT116) and epithelial nontumorigenic immortalized cells (HCEC-1CT). Results suggest that the lipid extracts have a selective cytotoxic effect, reducing the viability of the colon carcinoma cells but not the nontumorigenic cells. Thus, this multidisciplinary approach sheds light on the microalgae lipidome, and at the same time, provides new eco-innovative methods for extracting valuable lipids enriched in n-3 and n-6 LC-PUFA from microalgae with promising biological properties.