Measuring and Predicting Thermodynamic Limitation of an Alcohol Dehydrogenase Reaction

Abstract

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 (Km) 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 Km strongly depends on the initial reactant molalities...