Heteroprotein complex coacervates of ovalbumin and lysozyme: Formation and thermodynamic characterization

The formation of heteroprotein coacervates obtained by the interaction of ovalbumin (Ova) and lysozyme (Lys) was investigated using turbidimetric analysis and the zeta potential at different protein ratios, pH values and concentrations of NaCl. The complexes were formed over a wide pH range with a 1:1 (Ova:Lys) ratio and the highest turbidity was observed at pH 7.5, which optimal biopolymer interactions occurring. The addition of NaCl disfavored formation, even at low concentrations, and suppressed it at 300 mM. The complex coacervate formation occurred in the region between the isoelectric points (pI) of the proteins, predominantly by electrostatic interactions but with participation of hydrogen bonds. The structures formed had an average size of ∼2 μm, which was well above the isolated proteins, and microscopic analysis revealed that the complexes had a globular structure. The interaction was exothermic and spontaneous with a favorable entropic and unfavorable entropic contribution during interaction.