Valorization of pelagic Sargassum as a source of alginate and sugars for subsequent biofuel production

Abstract

Over the last decade, massive tides of Sargassum, a genus of brown algae, have arrived at Caribbean shores deriving in a myriad of environmental and economic problems. Aiming to lessen the impacts, governments from the affected countries have opted to remove the seaweed from marine ecosystems. However, its collection is expensive, posing another economic challenge for the already affected countries. Biomass valorization has been proposed as a suitable alternative to funding cleaning activities, triggering numerous investigations in recent years. Albeit different pathways have been suggested, Sargassum biomass has failed to find effective uses in the industry. This study aims to maximize the value of Sargassum as a potential raw material into a biorefinery scheme to produce alginate and sugars, considering this last product for subsequent biofuels production. Findings indicate that alginate extraction and sugar production can be effectively coupled within the same valorization scheme and that their integration also results in sugar maximization after biological pretreatment. The alginate extraction and purification process resulted in high polymer yields (38.75% ± 0.93 dry weight). The final product was found to be free of toxic elements opening the doors for its application in different fields. Lastly, Sargassum sugars extracts did not inhibit the growth of Yarrowia lipolytica, an oleaginous yeast, suggesting that they can be subsequently converted into biofuels.