Influence of ionic liquids on enzyme-catalyzed reactions

• Applicant: Privatdozent Dr.-Ing. Christoph Held
• Subject Area: Biological Process Engineering ; Chemical and Thermal Process Engineering
• Term: from 2015 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 282610332

Enzyme-catalyzed reactions become more and more important for the development of new alternative synthetic routes in biotechnological processes. However, the reaction equilibrium of many enzyme-catalyzed reactions is often far on the side of the substrates, since the conversion is thermodynamically limited. In such equilibrium-limited reactions, the substrate concentrations are typically increased in order to maximize yields. However, this method is often not or only partially applicable due to low solubility of hydrophobic substrates in aqueous reaction media. The conversion of equilibrium limited enzymatic reactions can be optimized by the presence of ionic liquids (ILs) in the reaction medium. In this proposal ILs will be used as additives to aqueous reaction media in order to shift the reaction equilibrium to the product side. In addition, substrate solubilities can significantly be increased upon addition of ILs in the reaction medium, thus conversion and selectivity of enzyme-catalyzed reactions can be systematically improved. Furthermore, the ILs can affect the catalytic enzyme activity. For investigations of the reaction equilibrium the enzyme activity has to be ensured under the respective reaction conditions (temperature, pH, IL-concentration). Individual studies of all three effects already exist in the literature, however so far they have only been considered separately for a low number of reactions and not systematically. This research project will contribute by a systematic thermodynamic study of these phenomena (reaction equilibrium, substrate solubility, enzyme activity) to a better understanding of the influence of ILs on enzyme-catalyzed reactions. These properties will be determined experimentally; reaction equilibria and substrate solubilities will also be predicted with a thermodynamic model. The enzyme activity is tested for the respective reaction conditions in order to verify the attainment of thermodynamic equilibrium. For a better understanding of the IL-effect on the enzyme activity the effect of ILs on the thermodynamic stability and on the secondary structure of the enzymes of the investigated reactions will be measured.In order to achieve general knowledge, two different enzyme-catalyzed reactions are considered, each having industrial relevance. In addition, four ILs are studied with respect to their influence on the equilibrium of enzyme-catalyzed reactions, substrate solubility and enzyme activity. These ILs differ in basicity / hydrophobicity / molar mass in order to investigate basically the influence of these properties on reaction equilibrium, substrate solubility and enzyme activity.This research project will contribute significantly to the understanding of the influence of additives of different chemical natures on the thermodynamics of enzyme-catalyzed reactions. In addition, there will be specific quantitative results on the use of ILs as additives for biological reactions.

• DFG Programme: Research Grants