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Thermodynamics of enzyme-catalyzed reactions in organic media


Dicarboxylic acid esters are interesting components and are widely synthesized for different applications. In the family of dicarboxylic acids, succinic acid is promising because it serves as a renewable resource. Dicarboxlyic acids can be produced biotechnologically in enzymatic reactions. Thus, the aim of this project is to investigate the thermodynamics of the Lipase-catalyzed esterification of dicarboxylic acids with alcohols. Reaction equilibria will be measured and modeled at different reaction conditions.



Dicarboxylic acids such as succinic acid are reported as promising components and renewable platform chemicals for several derivatives that are of industrial interest [1]. Their esters have very interesting thermo-physical properties and might be used as intermediates for the production of bio-based polymers [2]. In the specific case of esterification with ethanol, the reaction takes place sequentially with monoethyl carboxylate as intermediate product and diethyl carboxylate as the final product.

Mono- and diethyl carboxylates can be synthesized chemically and via an enzymatic pathway through Candida antarctica Lipase B (Novozym 435). The major goal of this project is to characterize thermodynamic properties of the enzymatic reaction route and reaction equilibria at different reaction conditions like temperature, pH, reactant and enzyme concentrations. Therefore it is necessary to determine the Gibbs energy of reaction which can be correlated to the measured apparent equilibrium constant. For this, It equilibrium concentrations of the reactants and products as well as their activity coefficients have to be known. Prior investigations on other enzyme-catalyzed reactions have shown that simplifications and assumptions of ideal behavior may cause high deviations of determined Gibbs energies of reaction to real Gibbs energies of reaction.

The outline of this project will be to determine thermodynamic characteristics like Standard Gibbs energies of reaction and the equilibrium constants of the enzymatic esterification. The experimental data will be compared with modeling by the PC-SAFT equation of state. This includes investigations on the esterifications at different reaction conditions (T, pH, initial reactant concentration). This will give further knowledge about Lipase-catalyzed reactions and the influences of reaction conditions on these kind of systems.



[1] Orjuela, Alvaro; Yanez, Abraham J.; Santhanakrishnan, Arati; Lira, Carl T.; Miller, Dennis J.:
"Kinetics of mixed succinic acid/acetic acid esterification with Amberlyst 70 ion exchange resin as catalyst"
Chemical Engineering Journal vol. 188, pp. 98–107, 2012
[2] Kolah, Aspi K.; Asthana, Navinchandra S.; Vu, Dung T.; Lira, Carl T.; Miller, Dennis J. (2008):
"Reaction Kinetics for the Heterogeneously Catalyzed Esterification of Succinic Acid with Ethanol"
Industrial & Engineering Chemistry Research, vol. 47, pp. 5313–5317, 2008



Foto von PD Dr.-Ing. Christoph Held

PD Dr.-Ing. Christoph Held


TU Dortmund
Fakultät Bio- und Chemieingenieurwesen
Emil-Figge-Str. 70
44227 Dortmund

Raum G2-513