Partitioning Behavior of Lysozyme and α-lactalbumin in Aqueous Two-Phase System Formed by Ionic Liquids and Potassium Phosphate

Abstract

Nowadays ionic liquids (ILs), because of their “green” characteristics, have been used for analytical and separation processes. Therefore the partitioning of lysozyme and α-lactalbumin using aqueous two-phase systems (ATPSs) composed of an ionic liquid (chloride 1-ethyl-3-methylimidazolium) and inorganic salts (K2HPO4, KH2PO4) was studied. Phase equilibrium diagrams were obtained to explore the effect of the different temperatures (293.15, 303.15, 313.15, and 323.15) K and pH (7.5, 8.0, and 8.5) used for the partitioning studies. For both proteins, partition coefficients decreased with increasing temperature. The pH influenced the partition coefficients of lysozyme and α-lactalbumin. The thermodynamic parameters (ΔH◦, ΔS◦, ΔG◦) indicate thermodynamic differences between the partitioning of lysozyme and α-lactalbumin in this system. The ΔH◦, ΔS◦, and ΔG◦values of the process studied showed that this process is spontaneous. This work demonstrates the possible use of ATPSs with ILs and inorganic salts as a methodology for the partitioning of lysozyme and α-lactalbumin.

Thermophysical Properties of 1-Ethyl-3-Methylimidazolium Chloride Solution From 293.15 to 323.15 K

“…Aqueous solutions of 1-ethyl-3-methylimidazolium chloride ([C 2 mim]Cl) were prepared using an analytical balance M254A (Bel Engineering) with an accuracy of ± 0.0001 g. Stock solutions of 1-ethyl-3methylimidazolium chloride (w = 0.50) were prepared for each pH value (7.5, 8.0 and 8.5) by addition of hydrochloric acid or potassium hydroxide when required. These pH values were chosen because they are commonly used in ATPS for separation of biomolecules (Sampaio et al, 2017). Appropriate quantities of the stock solution were diluted in tubes and shaken manually to obtain the desired mass fraction w = (0.05, 0.125, 0.2, 0.275 and 0.35).…”