Thermodynamic modelling of the partitioning of lysozyme in aqueous two-phase systems composed of polyethylene glycol and salt at different temperatures

Abstract

Knowledge about the interactions during the protein transfer is necessary to optimize the application of aqueous two-phase systems (ATPS) in purification processes. Theoretical knowledge combined with modelling and simulation can help to select the systems with the best partition values. Therefore, this study aimed to determine new interaction parameters through the contribution groups of lysozyme, using UNIFAC (Universal Functional Activity Coefficient) modelling. First, the partition of lysozyme was carried out, and the polymer molar mass (4000 or 6000), and the effects of the type of salt (Na2SO4 or Na3C6H5O7), the overall composition of the system (3 mooring lines), and temperature T = (293.15, 298.15, 303.15 and 308.15) K were evaluated. The results showed that lysozyme had a preference for the bottom phase of the ATPS system, the increase in the overall composition led to a tendency of increasing the partition coefficient (Kp), and the systems made up of higher molar mass polymers exhibited a bottom Kp value. The results of the thermodynamic parameters showed that the transfer of lysozyme in the phases was governed by entropy contribution. New interaction parameters of the contribution groups of lysozyme in the system phases were estimated. The UNIFAC model showed low deviation values. Therefore, the present results allow estimating new partitioning data for proteins presenting the same contribution groups, which can reduce the number of experiments and optimize the partitioning process.

Keywords

• Thermodynamic
• Partitioning
• Mass transfer
• UNIFAC