title: The role of microemulsions in lipase-catalyzed hydrolysis reactions.
abstract: The kinetics of the p-nitrophenyl butyrate hydrolysis reaction, catalyzed by Candida rugosa lipase in the water-in-oil microemulsion cetyltrimethylammonium bromide/water/pentanol/hexane, was investigated. The results described in the present manuscript reveal two peculiar characteristics of the reaction: (i) the initial rate of hydrolysis is very fast and (ii) by decreasing the water content of the microemulsion, the reaction rate approaches the typical behavior of reactions performed in aqueous solution. In particular, for microemulsion systems with a high water content, the end points of the reactions are dictated by the shape stability of the microemulsion. For these systems, our methodological approach shows that the process follows a second-order kinetics equation, indicative of the dual role played by water, which is involved both as a component of the microemulsion, i.e., relevant for the microemulsion stability and as a reagent of the hydrolysis reaction. In contrast, for microemulsions containing a small amount of water, after the hydrolysis reaction the system seems to fall in the no existence range of the microemulsion. Accordingly, the kinetics results are more complex: in the initial stage, the reaction follows a zero-order kinetics equation, while for longer reaction times a first-order kinetics equation fits the experimental data, as would be expected for an enzymatic reaction in a homogeneous system.
authors.affiliation: Dipartimento di Agricoltura, Ambiente Alimenti (DIAAA) and Consorzio Interuniversitario per lo Sviluppo dei Sistemi a Grande Interfase (CSGI), Università degli studi del Molise, Via De Sanctis, 86100, Campobasso, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Lopez
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Cinelli
authors.forename: Matilde
authors.initials: M
authors.lastname: Colella
authors.forename: Antonella
authors.initials: A
authors.lastname: De Leonardis
authors.forename: Gerardo
authors.initials: G
authors.lastname: Palazzo
authors.forename: Luigi
authors.initials: L
authors.lastname: Ambrosone
mesh_terms: D002087:Butyrates / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D000077286:Cetrimonium; D002593:Cetrimonium Compounds; D004655:Emulsions / Q000737:chemistry* / Q000378:metabolism*; D006868:Hydrolysis; D007700:Kinetics; D008049:Lipase / Q000737:chemistry* / Q000378:metabolism*; D008823:Micelles
chemical_list: D002087:Butyrates; D002593:Cetrimonium Compounds; D004655:Emulsions; D008823:Micelles; C033592:4-nitrophenyl butyrate; D008049:Lipase; D000077286:Cetrimonium
keywords: CTAB; kinetics; lipase; microemulsion