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

Abstract The role of enzyme engineering in biotechnol-

ogy, biological and pharmaceutical process cannot be over

emphasized. This study compared the adsorption of

digestives enzymes; amylase, protease and lipase on to Zn-

ferrite (ZnFe2O4). 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 character-

istic of metal ferrites. The adsorption of the amylase, lipase

and protease on ZnFe2O4 follow first-order kinetic model

with rate constants increasing with concentration. The

maximum adsorption capacities as revealed by the gener-

alized adsorption isotherms are 7.20, 42.90 and

22.24 mg g-1 for amylase, lipase and protease, respec-

tively, with cooperative binding. The Dubinin–Radushke-

vich model gave the maximum adsorption energies, E of

3.74 kJ mol-1 for amylase, 2.01 kJ mol-1 for lipase and

1.51 kJ mol-1 for the protease adsorption, showing that the

process is physisorption dominated. The isotherms fit the

adsorption data in the order of Freundlinch[General-

ized [Guggenheim–Anderson–de Boer[Tempkin

isotherm[Dubinin–Radushkevich. Thermodynamic study

revealed a spontaneous adsorption process with increased

entropy. ZnFe2O4, 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.

Keywords Adsorption -

 Enzymes -

 Zn-ferrite -

 Kinetic and

isotherm

Introduction

Adsorption of proteins on solid surfaces