Molecular thermodynamics of aqueous two‐phase systems for bioseparations

Abstract

Aqueous polymer-polymer two-phase systems provide a powerful method for separating biomolecules by extraction. When a complex mixture of biomolecules (e.g., a fermentation broth or a solution of lysed cells) is added to such a system, biomolecules partition uniquely between the two phases, achieving separation.A thermodynamic framework is presented for optimizing extraction performance in biological separations. First, a rnolecular-thermodynamic model, based on the osmotic virial equation, is proposed to describe phase equilibria for dilute aqueous mixtures containing polymers and protein. Second, experimental phase-equilibrium data (protein partition coefficients) are reported for a number of model proteins including albumin, lysozyme, and a-chymotrypsin. To interpret and correlate the experimental data, Low-Angle Laser-Light Scattering (LALLS) measurements were made to determine osmotic second virial coefficients for aqueous mixtures containing polymers, proteins, salts (KCI, KH,PO, and K,S04 at concentrations of 50 and 100 mM) and several combinations of polymer-polymer and polymer-protein pairs. Combined with electrochemical measurements (differences in potential between the two phases and protein net charge), these data provide parameters for the model to calculate the desired phase equilibria. A comparison of calculated and experimental results indicates that the virial-equation model provides good prediction of binodals and a reliable basis for estimating infinite-dilution protein partition coefficients for biotechnical process design.

The influence of thermodynamic activity on the solute rejection in multicomponent systems

“…The polymer-polymer interaction parameters have been fitted to experimental demixing data from the literature for the PEG3400/dextranTT0/water system [38]. Since the interaction parameters in the UNIQUAC model are based on a unit area of interacting surface, these parameters should apply for all poly(ethylene glycol)s and dextrans, independent of the molecular weight, provided that the molecules are linear and their conformations are equal to those for the PEG3400/dextranT70/water system.…”

Prediction of liquid-liquid equilibria for polyethylene glycol based aqueous two-phase system by ASOG and UNIFAC method

“…Edmond and Ogston (1968) proposed a virial expansion to predict phase diagrams of aqueous mixtures of Polyethylene glycol and Dextran . King et al extended this model and used for the prediction of biomolecule partitioning whereas Haynes et al (1989) included a higher order virial coefficient in the above model to obtain a phase diagram [King et al, (1988), Haynes et al, (1989), Wu et al, (1996)]. …”

Solubility of Amino Acids, Sugars, and Proteins

“…This methodology was adopted by King et al [82] and Haynes et al [76] to predict some protein partitioning in polymer-polymer mixtures in the presence or absence of salts. Wu et al [83] and Gaube et al [84], among other authors, performed similar studies.…”