Selective coacervation between lactoferrin and the two isoforms of β-lactoglobulin

Abstract

This work reports on the impact of subtle change of protein charge on coacervation and subsequent liquid–liquid phase separation between two oppositely charged globular proteins. For this purpose, a comparative study was conducted on the coacervation of lactoferrin (LF) with the two β-lactoglobulin (β-LG) isoforms. Upon mixing LF with an excess of β-LG, microspheres were formed throughout coacervation under narrow pH range (5.4–6.0). At the optimal pH of coacervation, LF being the limiting partner under tested concentration ranges. The β-LG/LF molar ratio recovered in the formed coacervates varied from 4 to 8 depending on the total protein concentration. Remarkably, LF showed a selective coacervation with isoform A of β-LG as judged by a larger concentration domain for coacervation and a high yield of LF recovered once mixed with β-LG A i.e. 80% against a maximum of 42% with β-LG B. At thermodynamic level, the interaction of LF with both β-LG isoforms exhibited complex exothermic binding isotherms with both enthalpic and entropic contributions.