Synthesis of thermo-responsive polymers recycling aqueous two-phase systems and phase formation mechanism with partition of ε-polylysine

Aqueous two-phase systems (ATPS) have the potential application in bioseparation and biocatalysis engineering. In this paper, a recyclable ATPS was developed by two thermo-responsive copolymers, P-VBAm and P-N. Copolymer P-VBAm was copolymerized using N-vinylcaprolactam, Butyl methacrylate and Acrylamide as monomers, and P-N was synthesized by N-isopropylacrylamide. The lower critical solution temperature (LCST) of P-VBAm and P-N were 45.0 degrees C and 33.5 degrees C, respectively. The recoveries of both polymers could achieve over 95.0%. The phase behavior and formation mechanism of P-VBAm/P-N ATPS was studied. Low-field nuclear magnetic resonance (LF-NMR) was applied in the phase-forming mechanism study in ATPS. In addition, combining the analysis results of surface tension, transmission electron microscopy and dynamic light scattering, the phase-forming of the P-VBAm/P-N ATPS was proved. The application was performed by partition of epsilon-polylysine in the 2% P-VBAm/2% P-N (w/w) ATPS. The results demonstrated that epsilon-polylysine was extracted into the P-N-rich phase, the maximal partition coefficient (1/K) and extraction recovery of pure epsilon-polylysine were 6.87 and 96.36%, respectively, and 7.41 partition coefficient and 97.85% extraction recovery for epsilon-polylysine fermentation broth were obtained in the presence of 50 mM (NH4)(2)SO4 at room temperature. And this method can effectively remove the most impurities from fermentation broth when (NH4)(2)SO4 exists in the ATPS. It is believed that the thermo-responsive recycling ATPS has a good application prospect in the field of bio-separation. (C) 2016 Elsevier B.V. All rights reserved.