Comparative adsorption of amylase, protease and lipase on ZnFe2O4: kinetics, isothermal and thermodynamics studies

Abstract

The role of enzyme engineering in biotechnology, biological and pharmaceutical process cannot be over emphasized. This study compared the adsorption of digestives enzymes; amylase, protease and lipase on to Zn-ferrite (ZnFeO). The metal ferrite was synthesized via a sol-gel technique and characterized with scanning electron microscopy (SEM), X-ray diffraction (XRD), Electron paramagnetic resonance (EPR) and Fourier transform infrared spectroscopy (FTIR). The adsorption was studied in a batch process and the data were subjected to kinetics and isotherm models. Characterization shows that the particle has a nanoporous structure, with pore sizes of about 5.4 nm and good magnetic properties. The FTIR data showed the presence of M-O bond, which is a characteristic of metal ferrites. The adsorption of the amylase, lipase and protease on ZnFeO follow first-order kinetic model with rate constants increasing with concentration. The maximum adsorption capacities as revealed by the generalized adsorption isotherms are 7.20, 42.90 and 22.24 mg g for amylase, lipase and protease, respectively, with cooperative binding. The Dubinin-Radushkevich model gave the maximum adsorption energies, E of 3.74 kJ mol for amylase, 2.01 kJ mol for lipase and 1.51 kJ mol for the protease adsorption, showing that the process is physisorption dominated. The isotherms fit the adsorption data in the order of Freundlinch > Generalized > Guggenheim-Anderson-de Boer > Tempkin isotherm > Dubinin-Radushkevich. Thermodynamic study revealed a spontaneous adsorption process with increased entropy. ZnFeO therefore, is a very good adsorbent for the purification of enzymes and can be used as a supporter for enzymatic process that required immobilization of the enzymes.