Tim Zeiner

Phase behaviour of hyperbranched polymers in demixed solvents

Hyperbranched polymers have attracted increased interest because of their tunable properties, which are affected by their architecture and a wide range of different functional groups. Many applications of hyperbranched polymers have been proposed based on their liquid–liquid phase behaviour. In recent years, the Lattice Cluster Theory (LCT) has been used to consider the impact of the architecture on the phase behaviour of hyperbranched polymers. In the theoretical framework of the LCT, the chain architecture is included in the Helmholtz energy, so all derived properties are influenced by polymer architecture. Until now, the application of the LCT in the field of hyperbranched polymers has been limited to ternary systems composed of one polymer with an arbitrary chain structure, one trimer and one solvent. This paper aims to extend the LCT to a ternary system that includes two polymers with an arbitrary chain structure and one solvent occupying one lattice site. In contrast to previous studies, the ternary system consists of Boltorn H20 + butan-1-ol + water, where all of the binary subsystems show demixing behaviour. Whereas experimental data are reported in the literature for the binary subsystems Boltorn H20 + water and butan-1-ol + water, no experimental information is available for the binary subsystem Boltorn H20 + butan-1-ol. Therefore, the phase behaviour of this subsystem was measured using the visual method. The paper discusses the possibility of predicting the ternary phase behaviour with the LCT in combination with the modified Wertheim theory based on knowledge of the phase behaviour of the corresponding binary subsystems. To verify the theoretical results, the ternary phase equilibria at constant temperature were also measured. In addition, the dependence of the thermodynamic properties on the special production lot of the commercially available Boltorn H20 is discussed.

Multistage aqueous two-phase extraction of a monoclonal antibody from cell supernatant

This article presents results of continuous multistage aqueous two‐phase extraction of an immunoglobulin G1 from cell supernatant in a mixer‐settler unit. An aqueous two‐phase system consisting of polyethylene glycol 2000, phosphate salt, and water was applied without and with sodium chloride (NaCl). Influences of different parameters such as throughput, phase ratio, and stage number on the extraction performance were analyzed. For systems without NaCl, the extraction was carried out as a washing step. An increase of stage number from one to five stages enabled to increase the immunoglobulin G1 purity from 11.8 to 32.6% at a yield of nearly 90%. Furthermore, a reduction of product phase volume due to a higher phase ratio led to an increase of purity from 20.8 to 29.6% in a three‐stage countercurrent extraction. For experiments with NaCl moderate partitioning conditions were adjusted by adding 8 wt% NaCl. In that case, the extraction was carried out as a stripping step.

Experimental Investigation of Laccase Purification Using Aqueous Two-Phase Extraction

In this paper the partitioning behavior of laccase from a culture supernatant of a Pleurotus sapidus fermentation in an aqueous two-phase system (ATPS) of polyethylene glycol with a molecular weight of 3000 g/mol (PEG 3000), potassium and sodium phosphate and sodium chloride is experimentally investigated. Results show that enzyme activity is retained during aqueous two-phase extraction. In addition the enzyme activity partitioning strongly depends on the sodium chloride concentration. The partitioning of impurities is not influenced with varying amounts of sodium chloride.

Solubility calculations of branched and linear amino acids using lattice cluster theory

In this work, the activity coefficients and the solubility of amino acids in water were calculated using the lattice cluster theory (LCT) combined with the extended chemical association lattice model allowing self-association as well as cross-association. This permits the study of the influence of the amino acids structure on the thermodynamic properties for the first time. By the used model, the activity coefficient and solubilities of the investigated fourteen amino acids (glycine, alanine, γ-aminobutyric acid, dl-valine, dl-threonine, dl-methionine, l-leucine, l-glutamic acid, l-proline, hydroxyproline, histidine, l-arginine, α-amino valeric acid) could be described in good accordance with experimental data. In the case of different α-amino acids, but different hydrocarbon chains, the same interaction energy parameter can be used within the LCT. All studied amino acids could be modelled using the same parameter for the description of the amino acid association properties. The formed cross-associates contain more amino acids than expressed by the overall mole fraction of the solution. Moreover, the composition of the cross-associates depends on temperature, where the amount of amino acids increases with increasing temperature.

Development of a generic process model for membrane adsorption

Abstract In this work, a generic model describing the dynamic adsorption behaviour of proteins on membrane adsorbers over complete purification cycles under consideration of module geometry and of the interaction between multiple transport mechanisms is developed. A general rate model for membrane adsorption, in which the interaction between multiple phenomena, like mass transfer and adsorption kinetics are considered, is formulated. Hereby, the implemented isotherms describe the influence of eluting agents on the adsorption behaviour, so that complete purification cycle (loading, washing and elution operation) can be simulated. Using the developed model the theoretical influence of relevant transport phenomena, operating conditions and process scale on affinity and ion exchange membrane adsorption of proteins are investigated. An example on ion exchange membrane adsorption illustrates the possibility to predict scale up effects occurring in configurations of multiple membrane adsorber modules. The obtained simulation results are in accordance with experimental observations reported in literature.

Integrated process development of a reactive extraction concept for itaconic acid and application to a real fermentation broth

Itaconic acid (IA) has a high potential to be used as a bio‐based platform chemical and its biocatalytic production via fermentation has significantly improved within the last decade. Additionally downstream processing using reactive extraction (RE) was described, potentially enabling a more efficient sustainable bioprocess producing IA. The bottleneck to overcome is the connection of up‐ and downstream processing, caused by lack of biocompatibility of the RE systems and direct application to fermentation broth. Within this study, a biocompatible RE system for IA is defined (pH dependency, extraction mechanism) and used for direct application to a fermentation broth. By optimizing the biocatalyst, the production medium, and the extraction system in an integrated approach, it was possible to define critical parameters that enabled a tuning of the overall bioprocess. With an extraction yield of YIA = 0.80 ± 0.03, IA could be produced as sole carboxylic acid ( b IA ,0 aq = 0.490 mol/kgaq) using a RE system consisting of ethyl oleate as organic solvent and tri‐n‐octylamine as extractant ( bT-C8 org = 0.6 mol/kgorg). This work is a proof of concept and demonstrates that by joint consideration of up‐ and downstream processing, optimized bioprocesses can be developed.

CHAPTER 16:Intensification of Aqueous Two-phase Extraction for Protein Purification

Within todays downstream processing of therapeutic proteins, there is an imminent need for alternatives to chromatographic separations, such as aqueous two-phase extraction. Challenges in the development and performance of aqueous two-phase extraction include a number of experiments to define appropriate process windows as well as enable multistage extraction. To reduce experimental effort, a hybrid thermodynamic model is presented in this contribution which allows the extraction system to be optimized with a smaller number of experiments. Moreover, multistage applications of aqueous two-phase extraction are presented to purify enzymes. To purify the investigated enzymes, two different apparatuses were used: namely, a mixer–settler unit and a centrifugal partition chromatograph.