Integrated biorefinery approach to valorise Saccharina latissima biomass: Combined sustainable processing to produce biologically active fucoxanthin, mannitol, fucoidans and alginates

The feasibility of European seaweed farming depends on the valorisation of algal biomass harvested. In the present work we have combined sequential extraction processes from Saccharina latissima to produce a range of products, focusing on the extraction of fucoxanthin using supercritical CO₂ followed by different valorisation routes. We optimised the conditions the for extraction of fucoxanthin (40 MPa, temperature has little impact on extraction) and the extracts obtained were tested on cancer cell cultures to determine the antiproliferative effects of this pigment. We established that the supercritical CO₂ extracts have an antiproliferative effect similar to that of commercial fucoxanthin (concentrations 0.1–0.4 mg/mL) and showed that the active compound in the extracts is fucoxanthin. In order to integrate this process with a holistic valorisation of the algal biomass, we explored the extraction of mannitol using a microwave-assisted protocol (4.15 wt % yield). We also evaluated the potential extraction of fucoidans and alginates from the solids remaining after supercritical CO₂ extraction (67.27 to 69.38 % of alginates). A life cycle analysis of the supercritical CO₂ extraction proposed shows that the drying process of algal biomass and the energy used to compress the CO₂ are the elements with the highest environmental impact (over 90% of CO₂ eq/g of extract) in this the process, indicating routes for reducing the environmental footprint. Combining supercritical CO₂ extraction and microwave-assisted extraction methods would enable European seaweed producers to obtain multiple marketable products from algal biomass.