Structure, rheology, and antifreeze property of the exopolysaccharide from Naematelia aurantialba through basidiospore fermentation

The quality of frozen food can be maintained with antifreeze. Commercial antifreezes like sucrose and glycerol are ineffective and may pose health hazards, making them inappropriate for use in food applications. A novel exopolysaccharide, xylomannan (NAPS-A), was purified from the fermentation broth of Naematelia aurantialba NX-20 in Tofu wastewater medium using anion exchange chromatography and Sephadex column chromatography. The analysis revealed that NAPS-A had a molecular weight of 2.924 × 10⁶ Da and was composed of mannose and xylose with trace amounts of glucuronic acid, glucose, and galactose. Its core structure contained 1,3-linked α-D-Manp residues as the backbone and branches at O-2 and O-4 of the β-D-Xylp residues. Furthermore, NAPS-A displayed remarkable thermal stability and shear-thinning phenomena, which are characteristic of non-Newtonian fluids. NAPS-A also exhibited significant antioxidant and antifreeze property. The findings in this study provide a chemical and biological basis for the potential development of NAPS-A as an antifreeze compound and functional food.