Driving forces for chymosin partitioning on the macromolecule-salt aqueous two phase system

Abstract

Aqueous two-phase systems (ATPSs) are strategic liquid–liquid systems for extraction and purification of compounds. However, only a few studies have evaluated the thermodynamic parameters that allow comprehension of the partition process of different molecules. Here, we investigated the chymosin (Chy) partitioning behavior in macromolecule + salt + water ATPSs by obtaining the partition coefficient (), Gibbs free energy change of transference (), enthalpy change of transference (), and entropy change of transference (), at infinite dilution, and their dependence on the ATPS properties. Chy transfer from the bottom to the top phase of the ATPS was enthalpically driven, with −4.84 kJ mol−1 < < −170.34 kJ mol−1 and −11.69 J mol−1 K−1 < < −558.95 J mol−1 K−1 characterizing an enthalpy–entropy compensation process; −1.36 kJ mol−1 < < −3.77 kJ mol−1. became more negative as the tie-line length increased, showing that specific macromolecule–Chy interactions determine the enzyme concentration in the top phase. The nature of the cation/anion, hydrophobic/hydrophilic balance of the top phase, and macromolecule molar mass influence the intermolecular interaction between Chy and top phase components, changing the enzyme partition behavior. Negative parameters were attributed to the Chy transfer from a higher (bottom phase) to the lower (top phase) configurational entropy region.