Development and optimization of a metabolite extraction process for the high throughput screening of microalgal chimiodiversity

Since a decade, using microalgae for biofuel has become a major challenge worldwide. Several studies have evidenced that potent bioactive molecules can be purified from microalgae for cosmetic or health applications (e.g. antioxidants, immunostimulants, anticancer and antiviral compounds) in order to upgrade biomass. In some species, extraction of bioactive metabolites is tricky for the presence of highly resistant cell walls (Phaeodactylum tricornutum) or exopolysaccharidic barriers surrounding the cell membrane (Porphyridium purpureum). It was therefore essential to develop a process that preserves sensitive molecules. We optimized an extraction grinding process, the Mix Mill process, based on the use of vibrating microbeads. The process efficiency was assessed in pigments extraction experiments. It gave excellent extraction yields, and combined fidelity (no modification of analytes), compatibility with HPLC and LC-MS analysis, accuracy, simplicity, rapidity and safety. Moreover, it allowed to simultaneously extract all pigments, whatever their polarity or the strength that linked them to the cell structures. As a conclusion, the Mix Mill process is a general process for the total extraction of microalgal metabolites thought for high throughput screening of the microalgal chimiodiversity.