(617bv) Centrifugal Partition Chromatograph: A Novel Continuous Multiphase Reaction System

Enzymatic reactions are of main interest due to their substrate specificity and gentle reaction conditions. However, substrates, which are poorly soluble in aqueous media, can be hardly catalyzed by enzymes due to the fact that most enzymes are active and soluble in aqueous media only. With the use of aqueous-organic two-phase reaction systems it is possible to continuously feed hydrophobic substrate, solved in the organic phase, and simultaneously remove product from the aqueous, catalytically active phase. Hence, product inhibition can be avoided and the reaction equilibrium shifted towards the product side.

To enhance the catalytic efficiency and long term stability as well as to enable continuous processing the biocatalysts are commonly immobilized. Unfortunately, most of the immobilization techniques reduce the initial catalytic activity of the system as steric and/or mass transport hindrances are present or the conformation of the enzymes changed after immobilization. Besides, multiphase reaction systems lead to different design aspects compared to monophasic aqueous systems. Efficient mixing to ensure the mass transport of substrate to the biocatalyst (reaction) and the product to the organic phase (product removal) is needed. For continuous processing a clear and continuous separation of the phases is mandatory to remove the product from the system without losing biocatalyst or product.

In recent years the Centrifugal Partition Chromatograph (CPC) as an alternative multiphase reaction device is investigated. Commonly the CPC is used for liquid-liquid chromatography, where one phase of a two-phase-system is immobilized in a chamber system that is arranged around a rotary axis. By rotating the system a centrifugal field is generated which keeps one phase of any two-phase system in the chamber cascade. The second phase is pumped through the stationary one and separation is commonly achieved via the partitioning of the components in the phase system. Due to the CPC set-up, the immobilization of biocatalysts in their natural environment, namely an aqueous solution, is easily feasible. The intense mixing of the two phases and the efficient phase separation for in situ product removal is ensured simultaneously. Hence, the CPC combines all design aspects for an efficient continuous multiphase reactor, namely immobilization of the biocatalyst, intense mixing, complete phase separation and in situ product removal in one compact device. additionally, as no solid phase is used to immobilize the biocatalyst structure changes due to covalent binding, loss of the hydrate shell or steric hindrances may not occur.

The present study will address the process design procedure to systematically select the phase system to achieve stable and efficient reaction rates and the CPC operation conditions to enable efficient mixing and separation of the phases. The procedure is applied to several biocatalysts ranging from enzyme to whole cell systems to produce pharmaceutical building blocks. The applicability of the CPC as a multiphase reactor is evaluated by comparing and discussing classical stirred tank reactor experiments.