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978-3-8439-2930-1, Reihe Verfahrenstechnik
Andres Kulaguin Chicaroux
Phasengleichgewichte und Stofftransport in polymerbasierten wässrigen Zwei-Phasen Systemen
169 Seiten, Dissertation Technische Universität Dortmund (2016), Softcover, A5
The downstream processing step is one of the most important process steps in the biotechnological production. Extraction in aqueous two-phase systems (ATPS) represents a promising technology for the downstream processing step as by the use of ATPS macro-biomolecules can be separated and purified under mild conditions. An ATPS can form when two hydrophilic incompatible components are mixed in water in sufficiently high concentration. Commonly used components of the ATPS are two hydrophilic polymers or a salt and a polymer. However, conventional ATPS have many drawbacks such as a high viscosity of phases in the ATPS based on linear polymers and the aggregation of macro-biomolecules in the ATPS containing salts. There exists therefore a demand for the ATPS with improved features. In this context hyperbranched polymers can be used to form the ATPS. Compared to linear polymers hyperbranched polymers show a lower solution viscosity and carry a higher amount of functional end groups.
In the present work the ATPS based on hyperbranched polyesteramide and dextran was characterized and compared with the conventional ATPS composed of dextran and polyethylene glycol. For this purpose, the phase behavior and the partitioning of an amino acid, L-serine, were studied in both the systems. Furthermore, the phase equilibria in the ATPS were modeled. The impact of polymer architecture was incorporated into thermodynamic model by Lattice Cluster Theory (LCT), whereas influence of functional groups on the phase behavior was considered by the use of Wertheim association model. This combination of the LCT und Wertheim association model was applied for the first time to quaternary mixtures in order to predict partitioning coefficient of amino acid in the ATPS. Besides the phase equilibria the knowledge of viscosity of phases, interfacial tension and mass transfer properties is crucial to design an efficient extraction process. For this reason, viscosity and interfacial tension of the ATPS were experimentally studied and additionally mass transfer experiments were carried out in the Nitsch stirred sell. Moreover, interfacial tension and mass transfer were theoretically studied. Interfacial tension in the ATPS was calculated with good accuracy using density gradient theory (DGT) and mass transfer in multicomponent mixtures could be successfully modeled by instationary version of DGT.