CHEMISTRY: Enantioselective Emulsions

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Science  10 Mar 2006:
Vol. 311, Issue 5766, pp. 1347c
DOI: 10.1126/science.311.5766.1347c

Although enzymes achieve extraordinary selectivity in catalyzing biochemical reactions, they operate in relatively dilute environments. To adapt enzymatic catalysis for cost-effective industrial-scale synthesis, it would be desirable to increase the reagent concentrations substantially. One approach has been to solubilize reagents by adding an organic co-solvent to aqueous solutions of the enzyme; however, the reaction rates in such biphasic systems are hindered by slow mixing kinetics.

Gröger et al. have used mini-emulsions to improve mixing efficiency by increasing the interface area between dissolved enzymes and substrates. They focused specifically on lipase-catalyzed kinetic resolutions of racemic α— and β— amino acid esters to the respective homochiral free acids. Through ultrasound sonication of aqueous solutions containing 1% surfactant and 1% hydrophobic hexadecane, the authors generated stable emulsions of 100-nm-diameter droplets containing the ester. The exceptionally high ester concentration under these conditions cut the reaction time to less than half that for a traditional biphasic system, while maintaining >99% enantioselectivity. — MSL

Angew. Chem. Int. Ed. 45, 1645 (2006).

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