Refining marine polysaccharides and their immunomodulatory effects

Abstract

Brown seaweed is a rich source of structurally diverse polysaccharides with promising bioactive properties. This study investigated in four ways how enzymatic refining can modify marine polysaccharides and influence their immunomodulatory effects. 1) A novel sulfatase, SulA1, cloned from a marine Arthrobacter strain, was characterized, and shown to selectively act on the chondroitin sulfate monosaccharide N-Acetyl-D-galactosamine-4-sulfate. This introduced the possibilities for the use of SulA1 in targeted desulfation strategies to alter bioactivity of targeted molecules. 2) Laminarin from three brown seaweed species (Laminaria digitata, L. hyperborea, and Saccharina latissima) was extracted and enzymatically modified. The laminarin derivatives were structurally analysed and found to distinctly regulate dendritic cell activity depending on their molecular size and branching pattern. These data suggest that different laminarin derivatives may have different therapeutic applications within the immune system. 3) Fucoidan from S. latissima was enzymatically refined into defined molecular weight fractions. The low molecular weight fucoidan fraction significantly suppressed the secretion of the pro-inflammatory cytokine by dendritic cells, indicating potential therapeutic applications against inflammatory diseases. 4) Two enzymatically generated alginate oligosaccharide fractions, enhanced cytokines secretion by dendritic cells and promoted Th1 responses in co-cultures with T cells. These findings highlight distinct immunomodulatory properties of alginate oligosaccharides with potential therapeutic relevance in inducing inflammatory responses, e.g. as adjuvants or in cancer treatment. Collectively, these results demonstrate that targeted enzymatic modifications can reshape the immunomodulatory activity of marine-derived polysaccharides, positioning them as promising candidates for therapeutic development. At the same time, this strategy enhances the efficient use of seaweed biomass and supports the creation of sustainable, high-value products with potential applications in pharmaceuticals and nutraceuticals.