Extraction of fucoidan and alginate from Sargassum thunbergii using dimethylamine solution: Insights into the process and mechanism

The utilization of algal ingredients for producing functional products has garnered significant attention. Furthermore, increasing the yield of polysaccharides has become a crucial point. In this work, the efficiencies of two-step extraction and co-extraction were compared, and dimethylamine solution was selected as the optimal extractant. Under the optimum extraction conditions (temperature of 75.00 °C, time of 3.15 h, liquid-solid ratio of 35.00 mL/g) determined by response surface methodology, the yield of alginate was 16.05 ± 0.37 % and the yield of fucoidan was 2.85 ± 0.08 %. Kinetic analysis of the extraction process was conducted using the shrinking core model, elucidating the rate and mechanism of product release. Additionally, it was demonstrated that the dimethylamine solution could be recycled for five times with stable extraction performance. The extraction mechanism was further analyzed by quantum chemical calculations, providing theoretical support for the extraction process of the products. The above results demonstrated that the higher yield of products extracted with dimethylamine was confirmed through experimental and quantum chemical analysis. Overall, this study provides a new perspective on the extraction of alginate and fucoidan from seaweed.