Simultaneous separation of egg white proteins using aqueous three-phase partitioning systems

Abstract

Egg white proteins (ovalbumin, ovotransferrin, lysozyme, ovoinhibitor and ovomucin) are used in a wide range of applications, thus requiring the development of cost-effective purification platforms for their isolation and recovery. In this work, aqueous biphasic systems (ABS) and three phase partitioning (TPP) were investigated as combined approaches to separate egg white proteins. ABS composed of poly(ethylene)glycol of different molecular weights and potassium phosphate buffer at pH 7 were first characterized and optimized to simultaneously separate ovalbumin and lysozyme. Within the ABS concept, there is the preferential partition of both proteins to the PEG-rich phase. However, by increasing the PEG molecular weight or phase-forming components content, there is the selective precipitation of lysozyme over ovalbumin at the ABS interface, falling within the TPP concept. The best TPP systems were then applied to separate proteins directly from egg white. With the best TPP identified, there is the fractionation of 3 main proteins from egg yolk, namely ovalbumin in the PEG-rich phase, lysozyme at the ABS interface and ovoinhibitor in the salt-rich phase. The obtained results reinforce the potential of ABS/TTP combined strategies to fractionate high-value proteins from complex matrices in a single-step.