Kinetic and thermodynamic parameters of immobilized glucoamylase on different mesoporous silica for starch hydrolysis: A comparative study

Large ordered mesoporous silica materials having different pore diameters were synthesized by hydrothermal method functionalized with 3-APTES and bifuctional agent glutaraldehyde. Aspergillus niger glucoamylase was immobilized onto mesosilica via simple adsorption technique and covalent binding. The bare and enzyme immobilized supports were characterized by low angle XRD, nitrogen adsorption studies, FT-IR spectroscopy, thermogravimetric analysis (TG) and scanning electron microscopy (SEM). Kinetic and thermodynamic parameters were evaluated for soluble starch hydrolysis. Kinetic parameters were calculated according to Lineweaver–Burk plot and Km value was found to increase and Vmax was found to decrease after immobilization. Activation energy for free enzyme was found to 20.43 kJ mol−1. The enthalpy of activation (ΔH), Gibbs free energy (ΔG substrate binding) and entropy of activation (ΔS) for soluble starch hydrolysis by glucoamylase are reported.