Antioxidant extracellular polysaccharide EPSLAN4 from marine-derived Limosilactobacillus fermentum LAN4 potential to against inflammation by inhibiting MAPK/NF-κB signaling pathway

Marine microorganisms have unique metabolic pathways due to their unique living environment, which enables them to produce many structurally special and highly active active substances. They are considered the most promising treasure trove of active substances for development. In this study, EPS_LAN4 was the extracellular polysaccharide (EPS) extracted from LAN4 which was identified as Limosilactobacillus fermentum isolated from seawater, sea mud, mangrove leaves, and soil. The yield of EPS_LAN4 was increased to 208 mg/L by optimizing fermentation conditions for LAN4 and purifying from the extracellular polysaccharides. Investigation for characterization of EPS_LAN4 revealed that the high content of glucose, mannose and glucuronic acid, and its helical structure contributed to its antioxidant activity. Furthermore, EPS_LAN4 effectively reduced the LPS-induced increase in NO, IL-6 and TNF-α expression in RAW264.7 macrophages by inhibiting the MAPK/NF-κB signaling pathway, indicating a significant anti-inflammatory activity of EPS_LAN4. Meanwhile, EPS_LAN4 at a low concentration also able to enhance the expression of NO, IL-6 and TNF-α in RAW264.7 cells. In general, these results suggested that marine-derived antioxidant extracellular polysaccharide EPS_LAN4 with immunomodulatory and anti-inflammatory activities is a potential raw material for modulating the immune system and anti-inflammatory drugs.