Submitted to: Journal of Molecular Catalysis B: Enzymatic
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/22/2007
Publication Date: 8/8/2007
Citation: Laszlo, J.A., Evans, K.O. 2007. Influence of self-assembled monolayer surface chemistry on Candida antarctica lipase B adsorption and specific activity. Journal of Molecular Catalysis B: Enzymatic. 48:84-89. Interpretive Summary: The design of systems employing enzymes to transform vegetable oil to new products requires greater in-depth knowledge of the steps involved in the transformation, as some of these steps have a tremendous impact on the speed at which the transformation occurs. Enzymes used for modifying oils usually are placed on some kind of inert support material, which allows the enzyme to be used repeatedly. In the present work, we have examined the importance of support material surface properties on the activity and structure of an enzyme. Changing support chemical properties from water-liking (hydrophilic) to water-repellant (hydrophobic) dramatically improved enzyme activity. This information will help us and our industrial collaborators to cost-effectively produce vegetable oil derivatives.
Technical Abstract: Immobilization of Candida antarctica B lipase was examined on gold surfaces modified with either methyl- or hydroxyl-terminated self-assembled alkylthiol monolayers (SAMs), representing hydrophobic and hydrophilic surfaces, respectively. Lipase adsorption was monitored gravimetrically using a quartz crystal microbalance. Lipase activity was determinted colorimetrically by following p-nitrophenol propionate hydrolysis. Adsorbed lipase topography was examined by atomic force microscopy. The extent of lipase adsorption was nearly identical on either surface (approximately 240 ng cm-2, but its specific activity was six-fold higher on the methyl-terminated SAM, showing no activity loss upon immobilization. A uniform, 5.5-nm high, highly packed monolayer of CALB formed on the methyl-terminated SAM, while the adsorbed protein was disordered on the hydroxyl-terminated SAM. Hydrophobic surfaces, thus, may specifically orient the lipase in a highly active state.