(214d) Integration of Enzymatic Reactions into Continuous Countercurrent Extraction Processes with Mixed Surfactant Solutions

Recently, the interest in aqueous surfactant two-phase systems for extraction purposes has grown. The fields of application lie thereby in the extraction and purification of metal ions, proteins, biomaterials, organic compounds and toxic aromatics from wastewater. Aqueous surfactant systems provide mild conditions for biomolecules sensitive to organic solvents or high temperatures. Thus, surfactant-basedsystems with an in-situ product removal to increase conversion are especially interesting for biocatalytic and biotransformation processes with regard to environmental friendliness. Reactive micellar processes are only rarely described in literature so far. Thereby, the utilization of aqueous surfactant two-phase systems for biocatalytic and biotransformation processes requires an operating temperature below the deactivation temperature of the biocatalyst and thus can be beneficial.

In this work, the feasibility of the continuous extractive biocatalysis with cloud-point extraction using mixed surfactant solutions is demonstrated for the first time. Thereby an enzymatic reaction (one step out of penicillin production) was integrated into a continuous extraction process. Since the reaction product was continuously removed, higher yields in comparison to batch experiments were reached. The flexibility of the mixed surfactant systems allows to tune the extraction systems to get the highest separation efficiency. Therefore basic studies regarding the phase behavior, phase separation kinetics and temperature-dependency of the mixed surfactant systems in regards of the continuous (reactive) extraction processes were performed. Further, the interaction between the surfactant and the enzyme in the reactive separation unit were studied.

The general applicability of the heterogeneous enzymatic catalysts in extraction columns, thus preventing the enzyme loss (a disadvantage of the homogeneous enzymatic catalysis) was demonstrated in this work. Thereby different concepts of integration of a heterogeneous biocatalysis in the extraction processes with surfactant-based systems and in continuous extraction columns in general were suggested. The concept of continuous heterogeneous extractive bioactalysis was extended to different types of columns and internals, whereas the usage of structured packings coated with the enzyme-containing gels seemed to be the most promising. Here the key influences of physical and structural properties in mixed surfactant systems were investigated. Additionally, the integration of micellar extraction with the whole cell biocatalysis was examined, using microalgae as a model system.

Summarizing, in this work the potential of the integration of biocatalytic reactions with enzymatic catalysis as well as whole cell biotransformations into continuous extraction with mixed surfactant solutions is revealed.