Hierarchical bimodal porous silicas and organosilicas for enzyme immobilization

This work shows the ability of a hierarchical porous silica-based network with pore systems at two different length scales for enzyme immobilization. Two different enzymes have been selected, lysozyme, a relatively small globular enzyme, and α-L-arabinofuranosidase, a large enzyme of interest in the winemaking industry. The lysozyme immobilization on several silica supports (bimodal porous silicas denoted UVM-7 materials and conventional silica xerogels) has been studied and the loading amounts can be correlated to the open nature and accessibility of the internal surface area. Bimodal UVM-7 silicas present a very quick adsorption rate and high enzyme loading. α-L-Arabinofuranosidase has been immobilized on nanoparticulated bimodal organosilicas with UVM-7 architecture. In this case we compare the results of electrostatic and covalent immobilization. The covalent immobilization allow us to shift the optimum enzymatic working conditions towards lower pH values and higher temperatures than the free enzyme, together with an increased resistance to high glucose and ethanol concentrations.