title: Enzymatic esterification in aqueous miniemulsions.
abstract: Monoesters of various linear carboxylic acids (C7-C12) with omega-phenyl-labeled primary alcohols (C1-C5) were synthesized in aqueous miniemulsions with various lipases as biocatalysts. The reactants were dispersed in an aqueous solution of a nonionic surfactant to form long-term stable miniemulsions. The esterification of all of the systems could be catalyzed by the applied enzyme and yielded significant conversions of about 90%. The hydrophilicity of the reactants and the specificity of the enzyme toward the substrates determine the reaction velocity and the final conversion. As a model system the reaction of nonanoic acid and 3-phenylpropanol was extensively studied. Among various lipases, Lipase PS was determined to be the most effective, and for this reaction the parameters were optimized. A maximum conversion of 80% could be obtained in less than one hour of reaction time. In comparison with an acid-catalyzed esterification performed in miniemulsion with the same reaction parameters, the enzyme-catalyzed reaction showed a significantly faster conversion. The reactions proved that the application of the miniemulsion technique enables efficient direct enzyme-catalyzed esterification reactions from carboxylic acids and alcohols in the presence of large amounts of water.
authors.affiliation: Max-Planck-Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
authors.forename: Eugen M
authors.initials: EM
authors.lastname: Aschenbrenner
authors.forename: Clemens K
authors.initials: CK
authors.lastname: Weiss
authors.forename: Katharina
authors.initials: K
authors.lastname: Landfester
mesh_terms: D002384:Catalysis; D004655:Emulsions; D004952:Esters / Q000138:chemical synthesis*; D057927:Hydrophobic and Hydrophilic Interactions; D007700:Kinetics; D008049:Lipase / Q000737:chemistry*; D013329:Structure-Activity Relationship; D014867:Water / Q000737:chemistry
chemical_list: D004655:Emulsions; D004952:Esters; D014867:Water; D008049:Lipase