title: 1H-NMR on line monitoring of water activity during lipase catalysed esterification.
abstract: 1H-NMR spectroscopy is used to determine simultaneously the water activity (aw) and the time course of an esterification reaction catalysed by a lipase. Chemical shifts signals of hydroxylic hydrogens in fast exchange (i.e the average hydroxylic signal of acid, alcohol and water) varies with water activity and ester content. Calibration curves have been established from model media composed of the substrates and various ester contents, at different water activities, in order to mimic a reaction medium. One relationship is established between water activity, hydroxylic hydrogen signal chemical shift and ester content. In order to estimate the water activity evolution as a function of time, this last relationship is applied to the hydroxylic hydrogen chemical shift measured in a reaction medium where the Rhizomucor miehei lipase in a powder form is suspended in the liquid substrates. This alternative way of determining the water activity based on hydroxylic hydrogen chemical shift presents some advantages over more classical means, i.e. time saved and inaccuracies avoided by monitoring without handling the sample.
authors.affiliation: Laboratoire de Génie Cellulaire, UPRES-A CNRS 6022, Faculté des Sciences, Université de Picardie Jules Verne, 33 rue Saint-Leu, 80039 Amiens Cedex, France.
authors.forename: B
authors.initials: B
authors.lastname: Decagny
authors.forename: C
authors.initials: C
authors.lastname: Roblot
authors.forename: F
authors.initials: F
authors.lastname: Ergan
authors.forename: C
authors.initials: C
authors.lastname: Sarazin
authors.forename: J N
authors.initials: JN
authors.lastname: Barbotin
authors.forename: J P
authors.initials: JP
authors.lastname: Séguin
mesh_terms: D020001:1-Butanol / Q000378:metabolism; D000438:Alcohols / Q000737:chemistry; D002210:Caprylates / Q000378:metabolism; D002264:Carboxylic Acids / Q000737:chemistry; D004951:Esterification; D004952:Esters / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism; D006859:Hydrogen / Q000737:chemistry; D006878:Hydroxides / Q000737:chemistry; D007700:Kinetics; D008049:Lipase / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D009090:Mucorales / Q000201:enzymology*; D014867:Water / Q000737:chemistry*
chemical_list: D000438:Alcohols; D002210:Caprylates; D002264:Carboxylic Acids; D004952:Esters; D005656:Fungal Proteins; D006878:Hydroxides; D014867:Water; D006859:Hydrogen; D020001:1-Butanol; C031356:hydroxide ion; D008049:Lipase; C031492:octanoic acid