Equilibrium study of immobilized lysozyme on the extrudate-shaped NaY zeolite

Studies of adsorption isotherms were used as a method of characterizing the adsorption behavior of the extrudate-shaped NaY zeolite for lysozyme in a reciprocal shaking water bath system. In equilibrium isotherm studies, the experimental data obtained either at different pH or with different ionic strength of buffer were fitted reasonably well by the Langmuir model. In parallel experiments, the influences of changes in temperature on the equilibrium isotherms were further investigated. With increasing temperature, different patterns of isothermal adsorption behavior for lysozyme were observed. When the temperature was lower than 310K, equilibrium isotherms were well correlated by the Langmuir model. However, at temperature higher than 323 K, equilibrium isotherms were well correlated by the Freundlich model. In addition, thermodynamic parameters (Delta G(ads)degrees, Delta H(ads)degrees, and Delta S(ads)degrees) for the adsorption process were also determined by using equilibrium association constant and van't Hoff relationship to analyze the experimental data. The results revealed that the use of extrudate-shaped NaY zeolite may be an ideal and promising support for the adsorption of lysozyme because of its low cost and simplicity of its preparation method. (c) 2005 Elsevier B.V. All rights reserved.