Optimization and evaluation of a simplified green biorefinery for alginate extraction from sugar kelp (Saccharina latissima)

A simplified two-stage ultrasound-assisted biorefinery process for sodium alginate extraction from sugar kelp (Saccharina latissima) was developed using green solvents. The process yielded three distinct fractions: fucoidan/laminarin (S1), sodium alginate (S2), and cellulose (P2). The results were analyzed with response surface methodology. Key parameters, including sonication amplitude, time, and pH, were evaluated, and sonication energy was introduced as a predictive factor to improve model accuracy. Mathematical optimization of the response surface model identified an optimal sodium alginate yield of 76.4 % at pH 2 and 432.2 kJ of sonication energy. Fourier-transform infrared spectroscopy (FTIR) confirmed effective sodium alginate fractionation, and molecular weight analysis correlated viscosity with alginate quality. Inductively coupled plasma mass spectrometry (ICP-MS) showed reduced heavy metal content in both fucoidan/laminarin and alginate, indicating an improved safety profile for potential food and nutritional applications. This scalable and eco-friendly biorefinery highlights an environmentally sustainable approach for sodium alginate production, maximizing biomass valorization and ensuring product safety.