Modelling of Liquid-liquid Equilibrium Behaviour of Aqueous Two-Phase Polymer Mixture System for Protein Extraction

Aqueous Two-Phase Extraction System (ATPES) has the potential to be an efficient yet inexpensive, large-scale separation techniques with short process development times for high-value protein because ATPES offers high yield and eliminates a large portion of the contaminating lysate. However, the realization of ATPES as a new protein separation technology at industrial scales is rather limited. Among the reasons are the fact that the selection of phase-forming agents can be exhaustive as there are many tuneable parameters, efforts are mostly empirical and intuitive with many possibilities and there are limited design approaches capable of accurate prediction of system and product behaviour that offer large scope of application with operation assessment and performance sensitivity. Hence, we propose a computational approach to represent and calculate the equilibrium behaviour of a common type of ATPES, i.e. aqueous polymer-mixture systems, to allow further study on its extraction potential. We present a Gibbs energy of mixing minimization approach to calculate the liquid-liquid equilibrium behaviour in the ATPES that is based on Flory-Huggins polymer theory [1,2]. We demonstrate the applicability of our approach by simulating the thermodynamic behaviour of water-PEG6000-DxT500 system. We briefly discuss some issues involved in solving for the LLE compositions and present methods and steps taken to achieve robust, accurate and reliable simulations. We solve the minimization problem using the modified Shor's R-algorithm for non-smooth optimization [3,4]. We compare our results with the calculations of Johansson et al. [5] and the experimental data of Albertsson et al. [6].