Optimised extraction and bioactivity of polysaccharides from Ascophyllum nodosum for industrial and agricultural applications

The growing demand for sustainable bioactive compounds has intensified research on macroalgal-derived polysaccharides for biomedical, food, and agricultural applications. Brown seaweeds are rich in polysaccharides such as laminarin, fucoidan, and alginate, which hold promise for diverse industrial applications. However, current industrial techniques of polysaccharide extraction produce up to 80% waste, highlighting the importance of adopting sequential extraction techniques. Ascophyllum nodosum, a seaweed native to Ireland with a long history of use in horticulture, was selected for the sequential polysaccharide extraction in this study. Conventional, solid-liquid extraction, microwave-assisted extraction and pressurised-liquid extraction were utilised to produce alginate and fucoidan + laminarin extracts. The yield efficiency, colour, cost, and biochemical content (polysaccharides and co-extracted phenolics and proteins) of each obtained extract were evaluated. Solid-liquid extraction showed 61.5% of biomass utilisation, highlighting the relevance of a sequential approach in polysaccharide extraction. Furthermore, the alginate composition was determined using a monoclonal antibody-based assay, showing potential to be a rapid, cost-efficient tool for alginate quality control. These findings provide preliminary guidelines for industrial-scale polysaccharide extraction optimisation. The extracts were subsequently tested for their effects on the model plant, Arabidopsis thaliana, subjected to no-stress, heat-, and fungal-stress. Compared to the control group, some extracts improved photosynthetic efficiency, growth, and modulated reactive oxygen species production. The latter of these effects suggests stimulation of the plant immune system, priming for protection against the many fungal pathogens that are increasing in prevalence in response to the changing climate, i.e. warmer and wetter conditions. This research underscores the commercial relevance of brown seaweed polysaccharides while highlighting their potential in sustainable agriculture in the face of increased temperatures leading to heat stress in the global climate change scenario.

Funder

European Union
Marine Institute
Cybercolloids Ltd.

Publisher

University of Galway

Rights

CC BY-NC-ND

cbn

Collections

University of Galway Theses (PhD Theses)