- Polysaccharides from algae are a highly diverse group of natural biopolymers that serve as essential structural and storage components in algal cell walls and play critical roles in marine ecosystems.
- These polysaccharides are structurally complex, often containing unique monosaccharides such as fucose, rhamnose, galactose, mannose, xylose, and uronic acids, and are frequently modified by sulfation, acetylation, or methylation. Their structural variety gives rise to distinctive physicochemical properties, making them valuable not only for algal physiology but also for food, pharmaceutical, cosmetic, and biotechnological applications.
- In red algae (Rhodophyta), the predominant polysaccharides are agar, carrageenan, and porphyran. These are sulfated galactans with gelling and thickening properties, widely used as hydrocolloids in food processing, microbiology, and biotechnology. Agar, for instance, has been central to microbial culture techniques, while carrageenans are widely employed as stabilizers and emulsifiers in dairy and processed foods. Beyond industrial uses, these polysaccharides exhibit bioactive properties such as antiviral, immunomodulatory, and antitumor activities.
- In brown algae (Phaeophyceae), key polysaccharides include alginate, fucoidan, and laminarin. Alginate, a linear copolymer of guluronic and mannuronic acids, is extensively used as a gelling, thickening, and stabilizing agent in food, textiles, and pharmaceuticals. Fucoidans are sulfated fucose-rich polysaccharides with significant biological activities, including anticoagulant, antioxidant, antiviral, and anti-inflammatory effects, making them subjects of intense biomedical research. Laminarin, a β-(1→3)-glucan with β-(1→6) branching, serves as a storage polysaccharide and has applications as a dietary fiber and immunomodulatory compound.
- In green algae (Chlorophyta), polysaccharides are more variable and include ulvans, sulfated heteropolysaccharides mainly from Ulva (sea lettuce). Ulvans are rich in rhamnose, xylose, glucuronic acid, and iduronic acid, and are studied for their antioxidant, anticoagulant, and immunomodulatory properties, as well as their potential as biomaterials for drug delivery, wound healing, and biodegradable packaging.
- Ecologically, algal polysaccharides play crucial roles in marine carbon cycling and ecosystem functioning. They contribute to the formation of dissolved organic matter, marine snow, and biofilms, serving as carbon sources for marine microbes and influencing global biogeochemical cycles. Sulfated polysaccharides in particular are adapted to the saline marine environment, helping algae withstand osmotic stress, desiccation, and pathogen attack.
- From an industrial and biomedical perspective, algal polysaccharides are considered sustainable, renewable, and multifunctional biomaterials. Their gelling, emulsifying, and stabilizing abilities make them indispensable in food and cosmetic industries, while their bioactivities position them as promising agents in pharmaceuticals, nutraceuticals, and regenerative medicine. Advances in biotechnology are now enabling extraction, modification, and structural analysis of these complex molecules, paving the way for tailored applications such as drug delivery systems, tissue scaffolds, and functional foods.
