Enhanced extraction of proteins using cholinium-based ionic liquids as phase-forming components of aqueous biphasic systems

Aqueous biphasic systems (ABS) composed of ionic
liquids (ILs) are promising platforms for the extraction and purification of
proteins. In this work, a series of alternative and biocompatible ABS composed
of cholinium-based ILs and polypropylene glycol were investigated. The
respective ternary phase diagrams, tie-lines, tie-line lengths and critical
points were determined at 25°C. The extraction performance of these systems for
commercial bovine serum albumin (BSA) was then evaluated. The stability of BSA
at the IL-rich phase was ascertained by size exclusion high-performance liquid
chromatography and Fourier transform infrared spectroscopy. Appropriate ILs
lead to the complete extraction of BSA for the IL-rich phase, in a single step,
while maintaining the protein's native conformation. Furthermore, to evaluate
the performance of these systems when applied to real matrices, the extraction
of BSA from bovine serum was additionally carried out, revealing that the
complete extraction of BSA was maintained and achieved in a single step. The
remarkable extraction efficiencies obtained are far superior to those observed
with typical polymer-based ABS. Therefore, the proposed ABS may be envisaged as
a more effective and biocompatible approach for the separation and purification
of other value-added proteins.