Partitioning of model proteins in aqueous two-phase systems containing polyethylene glycol and ammonium carbamate

The phase equilibrium and the partitioning of bovine serum albumin, trypsin and lysozyme in aqueous two-phase systems containing ammonium carbamate and polyethylene glycol 1500, 4000 and 6000 are presented in this communication. Partition coefficients, defined as the ratio of protein concentration in the polymer phase to that in the salt phase, vary in the range of 0.1–0.8 for bovine serum albumin, 1.0–2.4 for trypsin and from 2.3 to 9.0 for lysozyme, depending on the polymer chain size and on the tie-line length. The analysis of the separation factor, defined as the ratio of partition coefficients of two proteins, shows that high degrees of separation can be achieved. These results indicate that aqueous two-phase systems containing ammonium carbamate and polyethylene glycol can be an alternative to be considered for protein downstream processing.