Sulfated Exopolysaccharides from Porphyridium purpureum: A Review of Extraction, Structural Characterization, and Chemical Properties for Advanced Applications

<ns3:p> Microalgae are increasingly recognized as sustainable green cell factories capable of producing a various high-value bioactive compounds. Among them, the red microalga <ns3:italic>Porphyridium purpureum</ns3:italic> stands out for its unique ability to secrete sulfated exopolysaccharides (sEPS)—complex macromolecules enriched with sulfate and uronic acid groups that exhibit potent biological activities. These compounds function as natural antioxidants, immunomodulators, and antimicrobial agents, attracting substantial interest from the pharmaceutical, cosmetics, and functional food industries. A targeted literature search was conducted across the Scopus, PubMed, Web of Science and ScienceDirect databases to identify studies focusing on the extraction, structural characterization, and applications of sulfated exopolysaccharides from <ns3:italic>Porphyridium purpureum</ns3:italic> between 2015 and 2025. Recent research has demonstrated rapid advancements in environmentally friendly extraction technologies, including membrane filtration, three-phase partitioning (TPP), ultrasound-assisted TPP (UATPP), and deep eutectic solvents (DES), which collectively enhance the yield, purity, and preserve the biological functionality of sEPS. Furthermore, significant progress has been made in structural and mechanistic elucidation through advanced analytical and imaging techniques such as two-dimensional NMR spectroscopy, FTIR, methylation analysis, and transcriptomic profiling. These approaches have clarified how cultivation parameters and environmental stressors influence EPS biosynthesis, sulfation patterns, and biological activity. Overall, this review provides an integrated and forward-looking perspective on the scientific advances and technological challenges surrounding <ns3:italic>P. purpureum</ns3:italic> sEPS, outlining future directions toward sustainable bioprocessing and industrial valorization of these high-value biomacromolecules. </ns3:p>