Liquid−liquid equilibrium data and phase diagrams of new aqueous two-phase systems (ATPS's), composed of water + sodium hydroxide + poly(ethylene glycol) (PEG) of molar masses (1450, 4000, or 10 000) g•mol −1 , were determined at (288.2, 298.2, and 308.2) K. The effects of temperature and PEG molar mass on the equilibrium data were studied. It was found that an increase in temperature caused the expansion of the two-phase region and increased the slope and the length of the tie line. It was also observed that binodal curves shifted toward the origin with the increase in PEG molar mass.

Bovine a-lactalbumin (a-La) and lysozyme (Lys), two globular proteins with highly homologous tertiary structures and opposite isoelectric points, were used to produce bio-based supramolecular structures under various pH values (3, 7 and 11), temperatures (25, 50 and 75 C) and times (15, 25 and 35 min) of heating. Isothermal titration calorimetry experiments showed protein interactions and demonstrated that structures were obtained from the mixture of a-La/Lys in molar ratio of 0.546. Structures were characterized in terms of morphology by transmission electron microscopy (TEM) and dynamic light scattering (DLS), conformational structure by circular dichroism and intrinsic fluorescence spectroscopy and stability by DLS. Results have shown that protein conformational structure and intermolecular interactions are controlled by the physicochemical conditions applied. The increase of heating temperature led to a significant decrease in size and polydispersity (PDI) of a-LaeLys supramolecular structures, while the increase of heating time, particularly at temperatures above 50 C, promoted a significant increase in size and PDI. At pH 7 supramolecular structures were obtained at microscale e confirmed by optical microscopy e displaying also a high PDI (i.e. > 0.4). The minimum size and PDI (61 ± 2.3 nm and 0.14 ± 0.03, respectively) were produced at pH 11 for a heating treatment of 75 C for 15 min, thus suggesting that these conditions could be considered as critical for supramolecular structure formation. Its size and morphology were confirmed by TEM showing a well-defined spherical form. Structures at these conditions showed to be stable at least for 30 or 90 days, when stored at 25 or 4 C, respectively. Hence, a-LaeLys supramolecular structures showed properties that indicate that they are a promising delivery system for food and pharmaceutical applications.

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ATPS Molar mass PEG pH Phase diagram Whey protein a b s t r a c tThe partitioning of the whey protein lactoferrin, which is an iron transporter glycoprotein, in an aqueous two-phase system composed of poly(ethylene glycol) (PEG) and sodium citrate was evaluated. Equilibrium data at 25 • C were determined for each system studied using PEG with a molar mass of 1000 and 4000 g mol −1 at pH values of 5.5, 6.5, and 7.5. An increase in the molar mass of the polymer promoted the expansion of the two-phase region and caused the migration of the lactoferrin to the salt-rich bottom phase. An increase in pH also led to the expansion of the biphasic region. However, changing the pH over the tested range slightly affected protein partitioning. Lactoferrin recovery percentages greater than 94% were observed for all of the systems evaluated. The results indicated that lactoferrin can be successfully partitioned in an aqueous two-phase system formed of 14% (w/w) PEG and 10% (w/w) sodium citrate at pH 5.5 and 25 • C. The protein was concentrated 1000-fold in the salt-rich bottom phase in this system. of purity and recovery; and (iii) be efficient, effective, and economical for large-scale processes. Aqueous two-phase systems (ATPS) are an alternative for separating, concentrating, and purifying biologically active molecules such as proteins in complex mixtures. ATPS are formed by mixing either two polymers (such as poly(ethylene glycol)/dextran) or one polymer http://dx.