Enzymatic degradation of aqueous dextrans as affected by initial molecular weight and concentration

Dextrans with different initial molecular weights (IMW) ranging from 3.86 × 104 Da to 2.15 × 106 Da were enzymatically degraded by dextranase enzyme. The changes in weight-average molecular weight (Mw), polydispersity index (D value) and the percentage of 104–105 Da fragment of aqueous dextran were examined during 0–120 min enzymatic degradation. Results showed that the Mw of all dextran samples decreased with increasing enzymatic time. A significant molecular weight degradation occurred in dextran samples that had a higher IMW and at an early degradation stage. With increasing the degradation time, the percentage of the 104–105 Da in four dextran samples (Dex-270, Dex-1000, Dex-2000 and Dex-F) showed a remarkable growth at the beginning of the treatment (0–50 min). Experimental data indicated that all dextran samples (with different IMW and at different concentration) followed a second-order degradation kinetics. This study demonstrated a great potential for further production of low molecular weight dextrans with a more homologous molecular weight.