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Molecular thermodynamics of aqueous two‐phase systems for bioseparations
Author(s) -
King Robert S.,
Blanch Harvey W.,
Prausnitz John M.
Publication year - 1988
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690341002
Subject(s) - virial coefficient , chemistry , aqueous solution , polymer , thermodynamics , biomolecule , dilution , activity coefficient , phase (matter) , partition coefficient , extraction (chemistry) , aqueous two phase system , chromatography , organic chemistry , biochemistry , physics
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 molecular‐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 α‐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 (KCl, KH 2 PO 4 and K 2 SO 4 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.