Component analysis and utilization strategy of brown macroalgae as promising feedstock for sugar platform-based marine biorefinery

Brown algae have gained attention as a sustainable feedstock for biorefineries due to their ability to sequester carbon dioxide, rapid growth, and high carbohydrate content. The carbohydrate content in brown algae has only been analyzed for a few species, and in most cases, access to fundamental data such as sugar composition is limited, which hinders the assessment of brown algal biomass-based biorefining potential. In this study, the carbohydrate composition of brown algae (Undaria pinnatifida, Saccharina japonica, Ecklonia cava, and Ecklonia stolonifera) was analyzed in detail and application directions were proposed. As a result, alginate and glucan were detected in all resources, and the contents (alginate and glucan wt%) were as follows: U. pinnatifida (39.6 and 4.9 wt%), S. japonica (34.0 and 6.3 wt%), E. cava (24.3 and 7.7 wt%), and E. stolonifera (39.1 and 9.7 wt%). All feedstocks contain trace amounts (2.9–4.9 wt%) or no xylan-mannan-galactan. Mannitol was detected only in S. japonica (26.7 wt%) in rich, showing high potential as a biorefinery feedstock. We highlight that the carbohydrate composition of E. cava and E. stolonifera was analyzed for the first time and the potential use of brown algal biomass in a biorefinery approach.