Green biorefinery of Laminaria hyperborea industrial side-streams: Subcritical water extraction optimization via response surface methodology

Journal article, 2026

An integrated response surface methodology (RSM) approach for optimizing subcritical water extraction (SWE) of biopolymers and bioactive compounds from Laminaria hyperborea side-streams has been comprehensively developed. Temperature (110–140 °C), solid-to-liquid ratio (1:20–1:35 g:mL), and time (10–20 min) were evaluated on four key responses: yield, soluble protein, phenolic content, and molar mass. Temperature emerged as the most influential factor followed by extraction time and quadratic temperature effects. Building upon these findings, a multi-response optimization identified the targeted optimal conditions, achieving a desirability score of 0.802 under 130.2 °C, 1:28.5 g:ml, and 15.9 min. These conditions recovered up to 22% of the original biomass as an extract rich in fucose and uronic acids, indicative of fucoidan and alginate enrichment. Complementary downstream strategies demonstrated non-cytotoxicity, antioxidant and anti-inflammatory capacities in HaCaT keratinocytes. Findings encourage SWE adoption as a green technology in sustainable algal biorefinery and circular bioeconomy implementation.