Titania/lignin hybrid materials as a novel support for α-amylase immobilization: A comprehensive study

α-Amylase from Aspergillus oryzae was immobilized via covalent bonds and by physical interactions on a synthesized titania/lignin novel hybrid support. A temperature of 5°C, a pH of 7.0, an initial enzyme solution concentration of 3.0mg/mL and a 3h process duration were found to be optimal for the highest activity of the immobilized enzyme. Moreover, the effect of temperature, pH, storage time and repeated catalytic cycles on the activity of free and immobilized enzyme was examined. Bound α-amylase showed enhanced thermal and chemical stability, and its reusability was also improved. Immobilized α-amylase retained over 80% of its initial activity when stored for 30days at 4°C. Kinetic parameters of the free and immobilized biocatalyst were calculated and compared. The maximum reaction rate (V_max) and turnover number (k_cat) were slightly lower for the immobilized enzyme than for the free enzyme. It should be clearly stated that this work presents a useful protocol to produce stable and active immobilized α-amylase onto titania/lignin hybrid which may also be applied to immobilization of other enzymes.