Fuquan Chen

Alginate lyases are critical enzymes in hydrolyzing alginate into alginate oligosaccharides (AOS), which are bioactive compounds known for their antioxidant properties and ability to lower serum glucose and lipid concentrations. However, elucidating catalytic mechanisms and discovering enzymes with enhanced catalytic efficiency remain long-term challenges. Here, we report AlgL2491, a novel bifunctional and cold-adapted alginate lyase from Pseudoalteromonas carrageenovora ASY5, belonging to the polysaccharide lyase family 18. This enzyme uniquely cleaves both polyguluronic (polyG) and polymannuronic (polyM), predominantly releasing disaccharides, trisaccharides, and tetrasaccharides after 12 h of hydrolysis. The enzyme achieves peak catalytic efficiency at 35 °C and pH 7.5, with activity increasing 5.5-fold in 0.5 M of NaCl. Molecular dynamics simulations demonstrate that salt ions enhance structural stability by minimizing conformational fluctuations and strengthening interdomain interactions, providing mechanistic insights into its salt-activated behavior. The alginate oligosaccharides (AOS) exhibit excellent free radical-scavenging activities of 86.79 ± 0.31%, 83.42 ± 0.18%, and 71.28 ± 2.27% toward hydroxyl, ABTS, and DPPH radicals, with IC50 values of 8.8, 6.74, and 9.71 mg/mL, respectively. These findings not only reveal the salt-activation mechanism of AlgL2491 and highlight the potential value of its hydrolysate in antioxidant activity but also provide a sustainable industrial solution in industrial-scale AOS production directly from marine biomass, eliminating the need for energy-intensive desalination of alginate, which may inform future biocatalyst design for marine polysaccharide valorization.

Numerous compounds present in the ocean are contributing to the development of the biomedical field. Agarose, a polysaccharide derived from marine red algae, plays a vital role in biomedical applications because of its reversible temperature-sensitive gelling behavior, excellent mechanical properties, and high biological activity. Natural agarose hydrogel has a single structural composition that prevents it from adapting to complex biological environments. Therefore, agarose can be developed into different forms through physical, biological, and chemical modifications, enabling it to perform optimally in different environments. Agarose biomaterials are being increasingly used for isolation, purification, drug delivery, and tissue engineering, but most are still far from clinical approval. This review classifies and discusses the preparation, modification, and biomedical applications of agarose, focusing on its applications in isolation and purification, wound dressings, drug delivery, tissue engineering, and 3D printing. In addition, it attempts to address the opportunities and challenges associated with the future development of agarose-based biomaterials in the biomedical field. It should help to rationalize the selection of the most suitable functionalized agarose hydrogels for specific applications in the biomedical industry.