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

• Highly stable mesoporous silica support were synthesized by hydrothermal route and tuned to desire pore diameter with n-decane and without auxiliary chemical.
• Glucoamylase immobilized onto different mesoporous silica via adsorption and covalent binding was employed for the synthesis of industrially important glucose by the hydrolysis of starch.
• Kinetic and thermodynamic parameters of free and immobilized samples were estimated.
• The feasibility of the reaction was determined by different thermodynamic parameters.

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.

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