Simulation of the breakthrough curves for the adsorption of α-lactalbumin and β-lactoglobulin to SP Sepharose FF cation-exchanger

A simple lumped kinetic model was used to simulate the single- and two-component breakthrough curves for the cation-exchange adsorption of pure α-lactalbumin (ALA) and β-lactoglobulin (BLG) onto a 5-ml SP Sepharose FF column at pH 3.7 and flow rate of 2 ml min−1. When compared to equivalent experimental results, the model accurately predicted the single-component BLG adsorption profiles using Langmuir isotherm parameters (qm, maximum binding capacity of the adsorbent; Kd, dissociation constant for the protein–adsorbent interaction) obtained in batch experiments. The breakthrough curve for ALA, however, was well predicted only after increasing qm which indicates the occurrence of additional adsorption processes in the packed-bed relative to the batch system. An overshoot of the concentration of BLG in the bed exit stream observed experimentally in the two-component system, was only predicted after correcting the two isotherm parameters in order to account for the unexpected finding that the weakly bound ALA was able to displace the strongly bound BLG. A fitting mechanism was proposed for this situation. The correction factors employed for the pure binary mixture were used to simulate the breakthrough curves of the two proteins in experiments conducted with whey concentrate in each of the two stages of a novel separation process, and there was agreement between the experimental and theoretical results. These considerations should be helpful in developing a model compatible with the proposed mechanisms of adsorption for these two proteins.