Stability and repeatability improvement of horseradish peroxidase by immobilization on amino-functionalized bacterial cellulose

Bacterial cellulose (BC) is a biodegradable material with many excellent properties for enzyme immobilization. However, hydroxyl groups of low reactivity in glucose units cannot directly react with the amines of enzymatic proteins. In this work, amino-functionalized bacterial cellulose was firstly used as carrier to immobilize horseradish peroxidase (HRP) via glutaraldehyde coupling. SEM, FT-IR, XPS, BET, and TGA were used to characterize the properties of modified BC and showed that it is more suitable for enzyme immobilization. The optimum pH range for immobilized HRP (pH 5.5-8.5) was wider than that of free enzyme (pH 6-8), and the immobilized HRP exhibited good adaptability to environmental alkalinity. The relative activity of immobilized HRP at 25-40 degrees C was greater than 90%, significantly surpassing that of free HRP. Furthermore, the obtained kinetic constant values showed that modified BC had decreased affinity for the substrate. Additionally, modified BC-immobilized HRP was reused efficiently for 10 cycles with greater than 70% of its original activity retained. Under optimal conditions, coupling ratio and specific activity could reach 86.7% and 41.7 Ug(-1) min(-1), respectively. These results show that the immobilization of HRP on amino-functionalized BC enhanced its appropriateness for a future use in various biotechnological and environmental applications.