Abstract
The enzymatically catalyzed esterification reaction of propionic acid + 1-butanol ⇄ propionic-acid-butyl-ester + water inside an immobilizing hydrogel environment has been investigated by means of spectroscopically resolved nuclear magnetic resonance (NMR) imaging. The alginate hydrogel was in the shape of a 3-4 mm diameter bead, with both the gel-forming water and the solvent (cyclohexane) being fully deuterated to simplify the identification of small amounts of reactants. In the absence of enzymes, the self-diffusion process of the separate reactants (propionic acid and butanol) proved to be severely slowed down compared to pure Fickian self-diffusion, and the concentration buildup inside the gel bead was shown to depend strongly on the properties of the reactants. Two-dimensional, non-chemically resolved images revealed that the diffusion process is not radially symmetric as expected, thus complicating the modelling of the diffusion and reaction kinetics. The reaction itself has been observed with chemical resolution in a time series of up to 40 h, clearly demonstrating the reduction of 1-butanol and production of water inside the gel bead.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 235-246 |
| Number of pages | 12 |
| Journal | Applied Magnetic Resonance |
| Volume | 22 |
| Issue number | 2 |
| DOIs | |
| State | Published - 2002 |
Funding
We are grateful to B. Doumeche and M. Ansorge-Schumacher, Lehrstuhl fª Bio-technologie, RWTH Aachen, for preparing the gel samples and for continuing discussions. Financial support by the Deutsche Forschungsgemeinschaft within the scope of the Sonderforschungsbereich 540 ("Modellgestª experimentelle Analyse kinetischer Ph~inomene in mehrphasigen fluiden Reaktionssystemen") is gratefully acknowledged.
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics