| Abstract |
Cutinase from Fusarium solani pisi was encapsulated in sol-gel matrixes prepared using combinations of tetramethoxysilane and monoalkyl-methoxysilane precursors with different chain lengths (from methyltrimethoxysilane to n-octyltrimethoxysilane), in molar proportion of 1 to 5. The specific activity of the encapsulated cutinase in a model transesterification reaction in n-hexane has been correlated with the structure of the organically modified silica (ORMOSIL) support. The matrixes were characterized by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and by solid-state Si-29 and H-1 nuclear magnetic resonance (NMR). The enhancement of the bioactivity with increasing alkyl chain lengths UP to C-4 was correlated with the nature of the ORMOSIL surface groups, namely, with a decrease in the hydrophilic-lipophilic balance (HLB) of the matrix. Such trend suggests that the kinetics of the catalyzed transesterification in n-hexane is a diffusion-controlled process. For coprecursors with longer alkyl chains (C-6 and C-8), the activity of encapsulated cutinase suddenly falls, despite the continuous decrease in the matrix HLB. For the ORMOSIL with n-hexyltrimethoxysilane, in particular, the enzyme activity is zero, due to the alkyl chain acting as a pore blocker. This effect is more moderate for n-octyltrimethoxysilane, because the alkyl chain has a higher mobility within the inorganic matrix. |
