title: Water plays a different role on activation thermodynamic parameters of alcoholysis reaction catalyzed by lipase in gaseous and organic media.
abstract: The effect of water on the alcoholysis of methyl propionate and n-propanol catalyzed by immobilized Candida antarctica lipase B (CALB) has been compared in a continuous solid-gas reactor and in an organic liquid medium. The enthalpic and entropic contributions of water to the Gibbs free energy of activation in the gas phase were different from the ones in the organic phase, the inverse trends being observed for the variation of both DeltaH* and DeltaS* with water activity. Different phenomena were identified for their influence on the thermodynamic parameters. When increasing a(w), the enhanced flexibility of the enzyme was predominant in the gas phase whereas substrate-solvent interactions due to an increased polarity of the solvent affected mainly the thermodynamic parameters in the organic phase. The observed variations of DeltaG* with water activity were in accordance with kinetics results previously obtained in both reaction media.
authors.affiliation: Laboratoire de Génie Protéique et Cellulaire, Bâtiment Marie Curie, Pôle Sciences et Technologies, Université de la Rochelle, Avenue Michel Crépeau, 17042, Cedex 1, La Rochelle, France. mgraber@univ-lr.fr
authors.forename: Marianne
authors.initials: M
authors.lastname: Graber
authors.forename: Marie Pierre
authors.initials: MP
authors.lastname: Bousquet-Dubouch
authors.forename: Nadine
authors.initials: N
authors.lastname: Sousa
authors.forename: Sylvain
authors.initials: S
authors.lastname: Lamare
authors.forename: Marie Dominique
authors.initials: MD
authors.lastname: Legoy
mesh_terms: D002175:Candida; D002384:Catalysis; D019277:Entropy; D005656:Fungal Proteins; D005740:Gases; D008049:Lipase / Q000737:chemistry* / Q000378:metabolism; D012997:Solvents; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
chemical_list: D005656:Fungal Proteins; D005740:Gases; D012997:Solvents; D014867:Water; D008049:Lipase; C431349:lipase B, Candida antarctica