Enzymatic Degradation Behavior and Molecular Weight Regulation of Dextran: Empirical Modeling and Multi-Scale Structural Characterization

To meet the demand for controlled production of low-molecular-weight (Mw < 10 kDa) dextran with potential pharmaceutical applications, this study developed an efficient enzymatic preparation process using PC-Edex, a dextranase derived from Penicillium cyclopium CICC-4022. The effects of enzyme concentration, substrate concentration, temperature, and pH on the degradation of high-molecular-weight dextran were systematically investigated, and the optimal process conditions were established. A staged empirical control strategy based on the Malhotra model was developed to investigate and predict the behavior of dextran molecular weight changes during enzymatic hydrolysis. Under the optimized conditions, dextran with an Mw below 10 kDa was produced within 60 min, with the mass fraction of fragments smaller than 10 kDa reaching 94.56 ± 0.32% and the degradation rate exceeding 98.96 ± 0.15%. The resulting product exhibited a narrow molecular weight distribution (Mw/Mn = 1.528 ± 0.03) and adopted a compact random-coil conformation in aqueous solution. Multi-scale characterization results indicated that enzymatic degradation altered only the molecular weight of dextran, while the backbone structure, amorphous nature, and thermal stability were preserved. These findings present a robust and reproducible laboratory-scale process, which provides a reference for the industrial production of low-molecular-weight dextran for pharmaceutical purposes.