Tailoring the partitioning of proteins using ionic liquids as adjuvants in polymer-polymer aqueous biphasic systems

Aqueous biphasic systems(ABS)are promising for proteins purification;however,when dealing with samples comprising several proteins,the selectivity towards a target protein is difficult to achieve.In this work,the addition of ionic liquids(ILs)as adjuvants(5 wt%and 10 wt%)in ABS composed of polyethylene glycol(PEG)and dextran was investigated to tailor proteins partitioning between the coexisting phases.The liquid-liquid phase diagrams were determined at 298 K,followed by partition studies of three proteins(bovine serum albumin(BSA),immunoglobulin G(IgG),and cytochrome C(Cyt C)).Partition coefficients of IgG and BSA indicate the preference of both proteins to the dextran-rich phase,whereas Cyt C has no preferential partitioning between the phases.The addition of chloride-based ILs as adjuvants allows to increase or decrease the partition coefficients,thus tailoring the proteins partitioning between the phases.BSA partitioning essentially depends on the IL content in each phase,whereas Cyt C and IgG partitioning is ruled by the ILs chemical structure and established interactions.Molecular docking was carried out to address the ILs effect on the proteins partitioning,supporting experimental observations,while identifying the specific interactions occurring.The partition of each protein in polymer-salt ABS with ILs as adjuvants was determined,demonstrating the higher tailoring ability of polymer-polymer ABS when adding ILs.Finally,the partition of each protein in presence of the remaining ones was determined,as well as the selectivity of the studied systems to separate each pair of proteins,paving the way for their use in liquidliquid chromatography.

Aqueous Two-Phase Systems Applied to Partition Proteins from Goat Milk Whey In-Nature

The proteins coming from the milk whey have numerous functional properties. Among the proteins with high bioactivity, α-lactoalbumin (α-La) and β-lactoglobulin (β-Lg) are present in large quantities in the milk whey. In the separation process of proteins, it is important to choose techniques which besides ensuring purity and high yield will not affect the molecule biological activity. The aqueous two-phase systems (ATS) have been utilized with success in the partition of these proteins, however, the studies were performed using protein in its pure form. Studies using milk whey in-nature and goat milk whey have not been found yet. In this context, the objective of this study was to evaluate the liquid liquid equilibrium of aqueous two-phase systems (ATS) in the partition of α-La and β-Lg from goat milk whey in-nature. Equilibrium data were performed considering ATS comprised of polyethylene glycol, potassium phosphate and water at 25°C and pH 7.0. The influence of the polymer molecular weight and amount of goat milk whey in-nature on the partition coefficient of these proteins were assessed. The partition coefficient, selectivity, process yield and purity of α-lactoalbumin and β-lactoglobulin proteins were determined. The results showed that the separation technique by aqueous biphasic systems is applicable indicating high efficiency in the whey proteins separation process.