Study on Formation of Phosvitin-Fructooligosaccharide Complex and Stability Improvement Mechanisms

Phosvitin (PV) is a highly phosphorylated protein with strong metal-chelating capacity and bioactivity, but its application is hindered by poor environmental stability. In this study, fructooligosaccharides (FOS) were introduced to form a PV-FOS composite system. The interaction mechanism and structural-functional changes were assessed via thermal and pH stability tests, molecular docking, FTIR, circular dichroism (CD), particle size, zeta potential and changes in turbidity. SDS-PAGE and changes in solubility confirmed the coexistence of PV and FOS in the composite system. Molecular docking revealed that FOS with varying degrees of polymerization can bind to PV through non-covalent interactions to form a complex. FTIR showed characteristic peaks of both components, with shifts and intensity changes at 3200-3500 cm^-1, ~1650 cm^-1, and 1200-900 cm^-1, indicating that non-covalent interactions, intermolecular forces that may be hydrogen bonds, occur between amide, carbonyl, and phosphate groups of PV and hydroxyl groups of FOS. CD demonstrated slight secondary structure rearrangement of PV without significant denaturation. Compared with PV alone, the PV-FOS complex showed an increased particle size and a weakly negative surface charge, which could be attributed to the presence of FOS. These changes may enhance the anti-aggregation capacity of the complex. Consistently, turbidity measurements further demonstrated that the PV-FOS complex exhibited better turbidity stability. Functionally, FOS incorporation significantly improved PV's solubility, metal-chelating capacity, and lipid antioxidant activity under various temperature and pH conditions. In summary, FOS effectively complexes with PV via non-covalent interactions, thereby enhancing structural stability and functionality.