Process development for the extraction of biomolecules – Application for downstream processing of proteins in aqueous two-phase systems
The separation of complex mixtures consisting of multiple, partly characterized components is an industrial reality in downstream processing. Process development for protein purification therefore has to deal with this fact in an efficient manner. The best applicable pathway employs a combination of experimention and modelling of separation unit operations. Laboratory experiments are used to determine the separation feasibility with the fermentation broth as well as model parameters. For the application of liquid-liquid extraction to biotechnology processes, a process development concept and equipment comprising small scale mini-plant experiments as well as equilibrium stage and distributed-plug-flow modelling was developed. Exemplary results of this process development for a multi-stage integrated antibody capture with aqueous two-phase systems are presented.
Liquid-liquid extraction (LLE) has become an established unit operation in various chemical and also pharmaceutical processes. Biotechnology applications are mostly limited to classical white biotechnology products such as alcohols, acids and amino acids. Red biotechnology uses LLE e.g. for antibiotics (1). So far, large, complex, high value biomolecules, such as monoclonal antibodies, have not been purified by LLE as they irreversibly denature/precipitate when exposed to common organic solvents (2) (Figure 1).
Optimisations in upstream processing are constantly leading to rising titer concentrations as well as in some cases larger batch volumes and side component concentrations. On top of that the share of biologically derived products is rising. This leads to the so called downstream bottleneck (3-5). The available purification technologies are faced with capacity limitations, which currently are commonly overcome by increased equipment sizing (i.e. column volumes, membrane area etc.), which increases downstream costs. The costs of downstream processing are dominated by chromatography adsorbents, especially protein A (3). For this ...