Insights into a novel exopolysaccharide from Mariana Trench-derived Aspergillus versicolor SCAU214: Structure and immune activity.

A novel exopolysaccharide AVP-214-1was isolated and purified from the metabolites of a Mariana Trench-derived fungus Aspergillus versicolor SCAU214. AVP-214-1 exhibited a heteropolysaccharide architecture composed of mannose, galactose, and glucose residues. The linear backbone adopted α-(1 → 4)-linked d-galactopyranose and d-glucopyranose units with the following sequence: →[4,6)-α-D-Glcp-(1 → 4)-α-D-Glcp-(1] → [4)-α-D-Glcp-(1 → 6)-α-D-Glcp-(1 → 3)-α-D-Glcp-(1] → [4,6)-α-D-Glcp-(1 → 4)-α-D-Glcp-(1] → [4)-α-D-Glcp-(1] → [4)-α-D-Glcp-(1 → 4)-α-D-Galp-(1]→. Structural complexity arose from two distinct branching motifs: single α-d-glucopyranosyl and an α-D-mannopyranosyl, both attached via C-6 positions of the backbone residues 1,4,6-α-D-Glcp. The molecular weight of AVP-214-1 was determined to be 8277 Da. In functional assays, AVP-214-1 was found to significantly enhance the proliferation of RAW 264.7 macrophage cells and promote the secretion of cytokines, such as IL-6, TNF-α and IL-1β. Metabolomic analysis revealed that AVP-214-1 primarily influences pyrimidine metabolism and amino acid-related metabolic pathways, these metabolic pathways were likely related to immune regulation. These results suggest that AVP-214-1 from a Mariana Trench-derived fungus was a novel immune-stimulating polysaccharide, opening up new avenues for the development of bioactive polysaccharides from deep-sea organisms for potential biotechnological applications.