Complexes of glucose oxidase with chitosan and dextran possessing enhanced stability

Abstract

In this study, the different mole ratios of glucose oxidase/chitosan/dextran–aldehyde and glucose oxidase/chitosan/dextran–sulfate complexes were synthesized. The modification of glucose oxidase by non-covalent complexation with dextran and chitosan in different molar ratios was studied in order to increase the enzyme activity. The enzyme/polymer complexes obtained were investigated by UV spectrophotometer and dynamic light scattering. Activity determination of synthesized complexes and free enzyme were performed at a temperature range. The best results were obtained by C_chitosan/C_{dextran–aldehyde} = 10/1 ratio and C_chitosan/C_{dextran–sulfate} = 1/5 ratio that were used in thermal stability, shelf life, salt stress, and ethanol effect experiments. The results demonstrated that both complexes were thermally stable at 60 °C and had superior storage stability compared to the free glucose oxidase. Complexes showed higher enzymatic activity than free enzyme in the organic solvent environment using 10% ethanol. The complexes were resistant to salt stress containing 0.1 M NaCl or CaCl₂. The particle size distribution results of the triple complex evaluated the complexation of the chitosan, dextran derivative, and glucose oxidase. The average size of the triple complex in diameter was found to be 325.8 ± 9.3 nm. Overall findings suggest that the complexes of glucose oxidase, chitosan, and dextran showed significant enhancement in the enzyme activity.

Keywords:

• Chitosan
• dextran
• enzyme modification
• enzyme polymer complexes
• glucose oxidase