Liquid–Liquid Equilibrium Data of Aqueous Two-Phase Systems Formed by PEG + Potassium Phosphate + Water: Thermodynamic Modeling and Partition Study of <i>Canavalia bonariensis</i> Lectin

Aqueous two-phase systems (ATPS) are an effective alternative method for partial or total purification of biomolecules. Using thermodynamic models to determine the liquid–liquid equilibrium activity coefficient in ATPS facilitates the process of obtaining new liquid–liquid equilibrium (LLE) data. Moreover, understanding the interactions that occur during protein transfer is crucial to optimize the application of ATPS in recovering valuable compounds. In this work, UNIFAC modeling of PEG and potassium phosphate-based ATPS was performed. The energy interaction parameters calculated from the interaction between the contribution groups present in the systems allowed a comprehensive study of the forces driving phase separation. Additionally, partition experiments were carried out to evaluate the ability of these ATPS to purify the rCabo lectin. The lectin showed a low interaction with the polymeric top phase and remained most concentrated at the interface. The thermodynamic partition parameters showed that the transference process becomes enthalpically driven as the temperature increases. Therefore, the present results allow for the estimation of new LLE data for ATPS formed by the same contribution groups, which can reduce the number of experiments and optimize the use of ATPS in the partitioning process.