A successful biorefinery approach of macroalgal biomass as a promising sustainable source to produce bioactive nutraceutical and biodiesel

This study aimed to utilize four types of macroalgal biomass with a zero-waste biorefining concept for co-production of bioactive polysaccharide and biodiesel. The polysaccharide of macroalgal biomass obtained from Ulva spp., Sargassum spp., Cladophora spp., and Spirogyra spp. was extracted and partially purified by water-alcohol precipitation. The partially purified polysaccharide showed high antioxidant activity by scavenging DPPH and ABTS with IC₅₀ values of 3.50–37.31 mg/mL and 0.86–8.91 mg/mL, respectively, and high antiproliferative activity on human colon cancer cell line Caco-2 with IC₅₀ values of 0.66–12.20 mg/mL, while the antityrosinase activity was observed only Sargassum spp. and Cladophora spp. at 60.59% and 14.16%, respectively, at 10 mg/mL of tested polysaccharide extract. Interestingly, rare sugar including tagatose, psicose, and allose in polysaccharide were found to be 0.88–28.69 mg in 1 g of polysaccharide extract. After polysaccharide extraction, the macroalgal biomass residue was used to extract lipid prior to biodiesel production by acid-catalyzed transesterification. The extracted lipids of 3.09–10.05% were mainly composed of C16–C18 (>84%), and their biodiesel qualities were also satisfactory according to international requirements of biodiesel. It is expected that biorefinery approach will contribute greatly to zero-waste industrialization of macroalgal biomass-based bioactive nutraceuticals and biofuels.