Abstract

Hierarchical porous silica, particles or monoliths, were synthesized by polycondensation of sodium silicate in the presence of cetyltrimethylammonium bromide and ethyl acetate at different concentrations under hydrothermal conditions. They were used as the support for the immobilization of beta-galactosidase from Kluyveromyces lactis by adsorption. The enzyme loading capacity (higher than 50 mg?g-1 support) and the retention ability (lixiviation less than 20?% after 72 h of catalysis) of these supports were explained as a function of the hierarchical porosity, mesopore sizes of 1040 nm, and macropore sizes of 0.0720 mu m and the presence of ionized silanol groups on the surface. The optimum pH value and temperature for the maximum activity of the obtained hybrid biocatalyst were evaluated, indicating that the three-dimensional structure of the lactase was not significantly affected during the immobilization process. The stability under extreme conditions was improved in comparison with soluble lactase. The porous supports exhibited morphological and porous stability under the immobilization and catalytic processes. These results show that the obtained materials are good candidates for the immobilization of large enzymes, such as beta-galactosidase.