Silica nanowires with tunable hydrophobicity for lipase immobilization and biocatalytic membrane assembly

Silica nanowires (NWs) with tailored hydrophobicity are synthesized by capping different length of alkyl groups on surface via a one-pot anisotropic sol-gel growth approach. Lipase from Burkholderia Cepacia (BCL) is successfully immobilized onto the silica NWs via hydrophobic interaction. The specific activity of the immobilized BCL increases with the increasing length of the capping alkyl groups and surface hydrophobicity of the NWs. BCL immobilized onto the octadecyl groups-capped silica NWs displays the highest specific catalytic activity, which is also notably higher than that of BCL immobilized on octadecyl groups-modified mesoporous silicate. The superior performance can be ascribed to the combination of the interfacial activation of lipases induced by capped-octadecyl groups on the NWs and the improved mass transfer efficiency of reactants around the one-dimensional silica NWs. The BCL-loaded NWs are further used as "building blocks" to assemble filter paper-like biocatalytic membrane via vacuum-assisted filtration method. The free-standing biocatalytic membrane can be operated in a continuous mode to avoid the separation of catalyst from reaction products. This work provides new opportunity in enzyme immobilization and biocatalytic membrane preparation through using discrete silica NWs as supports and building blocks.