Crystallization and Biocatalysis
Crystallization is a frequently used technique within downstream processing and has repeatedly proven its applicability and cost effectiveness, especially on industrial scale. With detailed information about the physical-chemical properties of the relevant substances, including their phase diagrams, optimized crystallization processes can be designed, which facilitate high purities of the desired substances.
We investigate the direct integration of crystallization concepts into biocatalytic processes to overcome limitations in biocatalytic (cascade) reactions. Our main research focus is the application of in situ-product crystallization (ISPC) to selectively remove a desired product from a biocatalytic reaction. This in situ-product removal (ISPR) ‘pushes’ the biocatalytic reaction to the product side and therefore overcomes the original thermodynamically unfavorable equilibrium. The product can eventually be recovered from the reaction mixture by filtration. This concept can also be similarly applied for the removal of unwanted side products, which may otherwise interfere with the biocatalyst or downstream processing.
Compartmentalization and Biocatalysis
Compartmentalization is a powerful concept to entrap biocatalysts into or behind (membrane) materials to generate contrary reaction conditions for chemical or chemo-/biocatalytic reactions. The reactants typically pass through the semi-permeable materials to connect complex multicatalytic reaction networks. Herein especially enzyme-catalyzed reactions with incompatible reaction requirements can be combined and used for synthetic purposes.
In this concept we investigate UV-curing compartmentalization for the encapsulation of biocatalytic reaction systems. UV-curing provides at ambient temperatures a very high dispersion of the encapsulated aqueous domains, which facilitates a fast exchange of reactants and thus high catalytic performance. Both (partly) purified enzyme preparations and whole cell biocatalysts are used in such compartments for the synthesis of valuable products and intermediates.
Thermomorphic Solvent Systems and Biocatalysis
Thermomorphic solvent systems are specific solvent mixtures that exhibit a temperature-dependent miscibility gap, which allows the utilization of a reversible macroscopic phase change between mono- and multiphasic conditions. For systems with upper critical solution temperature-type phase behavior (UCST), monophasic reaction conditions at higher temperatures and an easy recycling of the biocatalyst after phase separation at lower temperatures can be achieved.
We study the liquid liquid phase equilibria of such ionic liquid/buffer/organic solvent-mixtures with UCST-type behavior and evaluate their usability for biocatalytic reactions. This reaction concept provides, in comparison to classical solvent systems, an improved biocatalytic behavior in combination with a simplified downstream processing approach. Here especially imidazolium- and cholinium-based ionic liquids show good to excellent applicabilities in such reaction systems.