Brown Seaweed Polysaccharide Extraction: Enzyme-Assisted Techniques and Magnetic Nanoparticle-Based Immobilization

Brown seaweeds are rich in bioactive polysaccharides such as laminarin, fucoidan, and alginate, which exhibit a wide range of biological activities and hold great potential for applications in the functional food and nutraceutical industries. In recent years, there has been a growing interest in developing advanced and sustainable extraction techniques to improve the recovery of these valuable compounds. While conventional methods – including Soxhlet extraction, hydrodistillation, and maceration – are still commonly used, they are often time-consuming, inefficient, and environmentally taxing. In contrast, innovative techniques such as enzyme-assisted extraction (EAE), microwave-assisted extraction, and ultrasound-assisted extraction offer faster, more selective, and eco-friendly alternatives. Among these, EAE has emerged as a particularly promising approach due to its efficiency, mild operating conditions, and ability to preserve the integrity of thermolabile compounds. However, challenges related to enzyme stability and reusability limit its industrial application. To address these issues, enzyme immobilisation has been explored, with magnetic nanoparticles (MNPs) gaining considerable attention as effective supports due to their large surface area, biocompatibility, and ease of magnetic separation. This review provides an overview of the biology of brown seaweeds and their major bioactive polysaccharides, followed by a critical evaluation of enzyme immobilisation methods. Particular emphasis is placed on the use of MNPs as supports for immobilised enzymes in the context of polysaccharide extraction. The integration of immobilised enzymes with green extraction technologies offers a promising route toward more efficient, sustainable, and scalable recovery of marine-derived bioactives.