ORIGINAL RESEARCH: An avidin-biotin immobilization approach for horseradish peroxidase and glucose oxidase on layered silicates with high catalytic activity retention and improved thermal behavior

Immobilization of horseradish peroxidase and glucose oxidase on biotinylated layered silicates resulted in high catalytic activity and improved thermal behavior. The immobilization approach involves a simple step, taking advantage of the high affinity of the biotinylated support to avidinylated enzymes. The K_m of immobilized horseradish peroxidase-avidin conjugate was different from the K_m of the native conjugate. Assuming Arrhenius behavior for the K_m, the activation energy, E_a, of the immobilized enzyme was 33.3 KJ/mol with a pre-exponential factor, A, 23 M. The values for the native enzyme-avidin conjugate were 16.8 KJ/mol and 0.04 M. The immobilization resulted in higher activity for the immobilized conjugate at higher temperatures compared to the native. Also, glucose oxidase-avidin conjugate immobilized on layered silicates exhibited improved thermal behavior. The immobilized enzyme conjugate retained 65% of its initial activity at 58°C, while the native conjugate retained 20% under the same conditions.