Measuring and Predicting Thermodynamic Limitation of an Alcohol Dehydrogenase Reaction

• Published in: Industrial & engineering chemistry research 2017-05, Vol.56 (19), p.5535-5546
• Main Authors: Voges, Matthias, Fischer, Florian, Neuhaus, Melanie, Sadowski, Gabriele, Held, Christoph
• Format: Article
• Language: English
• ISSN: 0888-5885; 1520-5045
• DOI: 10.1021/acs.iecr.7b01228

The knowledge of thermodynamic limitations on enzymatic reactions and of influencing factors thereon is essential for process optimization to increase space–time yields and to reduce the amount of solvent or energy consumption. In this work, the alcohol dehydrogenase (ADH) catalyzed reaction from acetophenone and 2-propanol to 1-phenylethanol and acetone in aqueous solution was investigated in a temperature range of 293.15–303.15 K at pH 7. It serves as a model reaction to demonstrate the use of biothermodynamics in order to investigate and predict limitations of enzymatic reactions. Experimental molalities of the reacting agents at equilibrium were measured yielding the position of reaction equilibrium (K m) at different reaction conditions (temperature, initial reactant molalities). The maximum initial acetophenone molality under investigation was 0.02 mol·kg–1 due to solubility limitations with a 1- to 50-fold excess of 2-propanol. It was shown that K m strongly depends on the initial reactant molalities as well as on reaction temperature. Experimental K m values were in the range of 0.20 to 0.49. Thermodynamic key properties (thermodynamic equilibrium constant, standard Gibbs energy and standard enthalpy of reaction) were determined by measured K m values and activity coefficients of the reacting agents predicted with the thermodynamic model ePC-SAFT. In addition, ePC-SAFT was used to predict K m at different initial molalities. Experimental and predicted results were in quantitative agreement (root-mean-square error of experimental versus predicted K m was 0.053), showing that ePC-SAFT is a promising tool to identify process conditions that might increase/decrease K m values and, thus, shift the position of reactions for industrial applications.