(272b) Polymeric Aqueous Two Phase System with an Immobilized Phase By Cross-Linking

In recent years, the production of biotechnological products has been increased steadily. Especially the production of proteins as enzymes and biopharmaceuticals has gained more and more relevance for our industrial production and our health system. Hereby, the upstream of the proteins in the fermentation process has improved, so that today a titer of several g/l target proteins in fermentation broths can be achieved. The bottleneck in the production process is the downstream process to purify the proteins. Today, the state of the art downstream process is a chromatographic platform process resulting in high protein purities, but showing some disadvantages concerning the scale-up and the high costs. For this reason, there is a need for alternative processes extraction processes. Hereby, it is essential, that the used solvents will maintain the biological activity of the proteins. Therefore, Aqueous Two-Phase Systems (ATPS) have been applied with the two phases consisting mainly of water. ATPS can be formed by the solution of two hydrophilic, but incompatible components in water as two polymers or a polymer and a salt, above a critical solution. Because of the different physical behaviour of the two corresponding phases, the target product and the impurities can be distributed differently on the two phases. But there are still some drawbacks like the phase separation in polymeric systems, the formation of emulsions or the lack of reliable models for prediction.

This work studies the modelling of polymeric ATPS with an immobilized phase. As model system, the ATPS composed of Polyethylene glycol (PEG) and Dextran was analysed, whereas the Dextran was immobilized. The model approach is based on the Koningsveldt-Kleintjens model forming the backbone of the swelling model. To model the ATPS with the immobilized phase a novel incompressible elastic term is introduced considering the elastic limit of the dextran chains. At first, the ATPS with free PEG and dextran chains were modelled with the Koningsveldt Kleintjens model and a good accordance to the experimental data was found. Afterwards, the Koningsveldt-Kleintjens model was combined with the developed elastic term. A sensitivity analysis of the model was conducted to identify the important model parameters. To verify the model, experiments were performed to analyse the swelling of the immobilized dextran and the sorption of the amino acid L-Serine in the immobilized phase. Thereby, the swelling and the sorption of L-Serine in the immobilized phase could be modelled in good accordance to the experimental data.

The results will be extensively discussed and a future outlook will be given.