Effect of surface charge conditions of carriers on the immobilization of β-d-glucosidase.

In this study, a series of acidic or alkaline polypeptide chains were designed and grafted onto DEG-AM resin using Fmoc solid-phase synthesis to study the relationship between enzyme conformation and carrier surface charge. β-d-glucosidase (βGase) was then immobilized onto these modified carriers by adsorption. Each form of immobilized Gase showed decreasing specific activity compared to that of the free. It could be attributed to both the changes in the enzyme conformation and the decrease in mass transfer efficiency. The optimum temperature of free Gase, DEG@B3-Gase is 55 °C, which of DEG@A3-Gase is 65 °C and they all have the highest activity at pH 5. The values ​​of free Gase, DEG@A3-Gase, and DEG@B3-Gase are 0.546 kJ/mol, 0.224 kJ/mol, and 0.446 kJ/mol, and the values were 1.30 mmol/L, 1.44 mmol/L and 2.63 mmol/L, respectively. It shows that free Gase and DEG@A3-Gase are more similar. Meanwhile, the free Gase (1.0 g/L, pH 5.0) stored at 4 °C has a shorter half-life (t), which is only 9 days. However, the half-life of DEG@B3-Gase and DEG@A3-Gase is 20 days and over 60 days, indicating that the negative charged surface was conducive to maintenance of the structure and catalytic property of Gase.