(283e) Rapid Selection of Optimal Systems for Aqueous Two-Phase Extraction - Using Excipients to Increase Solubility and Stability of High-Value Biomolecules -

Aqueous Two-Phase Extraction (ATPE) using an Aqueous Two-Phase System (ATPS) has long been shown to be a promising alternative in the purification of high-value biomolecules (e.g., biopharmaceuticals or industrial enzymes) from fermentation broth. Although offering a high biocompatibility, a gentle separation profile due to low interfacial tension, good scalability and high efficiencies, ATPE has not yet made it into an industrial application. This is due to several challenges typically arising from state-of-the-art ATPS selection: (1) The high experimental effort required to identify an ATPS by trial-and-error screenings. (2) The lack of knowledge gained upon using this approach regarding the influence of the ATPS composition on the conformational and colloidal stability and activity of the high-value biomolecule. Both facts most likely lead to the identification of a process window for the ATPE that performs below the requirements (e.g., precipitation / aggregation of the high value biomolecule).

Within this work we thus developed a physical sound approach addressing these challenges in ATPS selection. The approach is based on the knowledge of: (1) The molecular interactions in solution by defining potentially suitable ATPS components based on a predictive modeling approach using ePC-SAFT, a state-of-the-art equation of state. (2) The conformational stability of the biomolecule (by measuring the temperature of unfolding) in the presence of the ATPS solutes. (3) The colloidal stability of the biomolecule in the ATPS by investigating biomolecule-biomolecule (B₂₂) and biomolecule-solute (B₂₃) interactions. This allows for (1) an initial rapid identification of a suitable ATPS that shows high yield and selectivity during extraction, and (2) simultaneously optimizing this ATPS using suitable excipients to tune biomolecule solubility and stability within the ATPS.

Applying the approach for selection of a suitable ATPS for a monoclonal antibody (IgG) and an industrial dehydrogenase (cFL1, supplied by Georgia Tech, Bommarius Lab) demonstrates, that the time for ATPS selection can be reduced from several months to less than two weeks (including modeling and experiments). By additionally selecting appropriate excipients for the ATPE of both biomolecules, we were able to achieve a drastical improvement of the ATPE of IgG and cFL1. The amount of precipitated cFL1 (loss of functionality) was decreased from 60 to 7.5 wt% simultaneously increasing the yield from 20 to 87.7 wt% in comparison to a previous (by trial-and-error selected) ATPS.

The results demonstrate that the application of the approach will prospectively not only support the establishment of ATPE as purification technology, but also offers the opportunity to select optimized solutes for the whole industrial production process of high-value biomolecules.