La catalyse enzymatique en milieu organique Enzymatic Catalysis in Organic Media

• Main Author: Monot F.
• Format: Article
• Language: English
• Published: EDP Sciences 2006-11-01
• Series: Oil & Gas Science and Technology
• Online Access: http://dx.doi.org/10.2516/ogst:1994011
• ISSN: 1294-4475; 1953-8189

L'environnement naturel des enzymes étant de nature aqueuse, leurs applications industrielles se sont en général limitées à des réactions mettant en jeu des substrats solubles dans l'eau. Depuis quelques années, la possibilité de faire fonctionner des enzymes dans des milieux hydrophobes (hydrocarbures, solvants organiques) a été mise en évidence, engendrant ainsi de nombreux travaux visant, d'une part à mieux comprendre les mécanismes permettant aux enzymes de rester actives dans un tel environnement et, d'autre part à explorer les nouvelles applications envisageables. Les produits pétroliers constituant par excellence le domaine des molécules hydrophobes, le présent article se propose de faire le point sur ces deux aspects, compréhension et intérêt de la catalyse enzymatique en milieu organique. Nous détaillerons ainsi les vues actuelles sur le fonctionnement des enzymes dans des solvants organiques, les différents modes de mise en oeuvre possibles et, à travers une revue de leurs applications potentielles, les principaux systèmes enzymatiques utilisés. <br> The extension of enzymatic catalysis, classically carried out in aqueous media, to organic media can be first ascribed to the possibility of using substrates that are poorly soluble or insoluble in water. In biphasic media consisting of an aqueous phase containing the enzyme in solution and of a non water-miscible organic solvent, the enzyme is kept in a suitable aqueous environment. A variant biphasic system consists in creating reverse micelles by the addition of a surfactant in order to increase the interfacial area and thus to improve the transfers between the aqueous phase where the enzyme is located and the organic phase. In these two cases, the partition coefficient of the different reactants plays a crucial role by governing the rates and yields of reaction. Microaqueous media constitute a new system for biocatalysis in organic media. In this case, a solid enzyme is incorporated into an organic solvent, preferably a hydrophobic one, wherein it exhibits new properties, especially a higher stability and a modified selectivity. The enzymes the most studied in this type of medium are hydrolytic ones, such as lipases or proteases which can then catalyze synthesis reactions. Yet, other classes of enzymes have also been used in this way. As oil products are typical hydrophobic compounds, it was of interest in view of possible applications in the petroleum and petrochemical industries to report the present knowledge about the functioning of enzymes in organic media. The present and potential applications of the most studied enzymatic systems will be reviewed in order to point out the major points of interest of biocatalysis in organic media either for organic synthesis or for less investigated fields, such as, for instance, biodegradation of pollutants by whole cells.