Influence of the hydrophilic–hydrophobic contrast of porous surfaces on the enzymatic performance
Herein we report the dependency of the performance (uptake, activity, stability) of hydrophilic glucose-6-phosphate dehydrogenase (G6PDH) onto mesoporous cellular foams (MCF) grafted with aminosilanes of different chain length. The resulting hydrophobic–hydrophilic contrast was carefully evaluated by combined argon and water sorption and quantified with a newly developed hydrophilicity index suitable for the characterization of large-pore materials. The enzymatic behaviour was influenced by electrostatic and hydrophobic interactions between both reaction partners due to the creation of specific microenvironments inside the pore system. The microenvironment created by the materials with high hydrophobicity did not contribute to the beneficial electrostatic interactions of the charged amine groups by increased hydrophobic forces instead a competition of both forces was present. Thus an improved biocatalytic performance was not observed for materials with high hydrophobicity but short-chain functionalized MCFs led to highly stable and active biocatalysts.