Biochemical Engineering Journal 49 (2010) 221–228 Contents lists available at ScienceDirect Biochemical Engineering Journal journal homepage: www.elsevier.com/locate/bej Simulation of the breakthrough curves for the adsorption of -lactalbumin and -lactoglobulin to SP Sepharose FF cation-exchanger Mayyada M.H. El-Sayed ∗,1 , Howard A. Chase Department of Chemical Engineering & Biotechnology, University of Cambridge, Cambridge, UK article info Article history: Received 19 August 2009 Received in revised form 10 December 2009 Accepted 29 December 2009 Keywords: Simulation Simple kinetic model -Lactalbumin -Lactoglobulin Whey concentrate Packed-bed adsorption abstract A simple lumped kinetic model was used to simulate the single- and two-component breakthrough curves for the cation-exchange adsorption of pure -lactalbumin (ALA) and -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 (q m , maximum binding capacity of the adsorbent; K d , dissociation constant for the protein–adsorbent interaction) obtained in batch experiments. The breakthrough curve for ALA, however, was well predicted only after increasing q m which indicates the occurrence of additional adsorption pro- cesses 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. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Adsorption models for porous particles are based mostly on rate theories which consider only one rate limiting step, i.e. either the rate of adsorbate–adsorbent interaction or the rate of adsor- bate diffusion (pore or film) as controlling the overall adsorption mechanism [1–5]. Arve and Liapis [6] developed a sophisticated model for biospecific affinity chromatography considering three rate controlling mechanisms simultaneously, two for film and pore- diffusion mass transfer mechanisms and one for the interaction between adsorbate and adsorbent. Hortsmann and Chase [7] also used such a model to describe the adsorption kinetics of a series of paraquat–protein conjugates to an immunosorbent consisting of monoclonal anti-paraquat antibodies covalently immobilised to Sepharose 4B. In general, two main models have been proposed for the adsorption of proteins, namely the simple ‘kinetic rate constant’ ∗ Corresponding author. Tel.: +44 1223 363973; fax: +44 1223 334796. E-mail addresses: mmhae2@cam.ac.uk, mayyada@aucegypt.edu (M.M.H. El-Sayed). 1 Also affiliated to the National Research Centre in Cairo, Egypt. model which is based on a single lumped kinetic parameter, and the more rigorous ‘pore-diffusion’ model which considers the individual transport processes occurring prior to the adsorption reaction, by taking into account diffusion across the liquid film surrounding individual particles and also the diffusion within the ion-exchanger particle itself. Regarding the modelling of whey pro- tein adsorption, James [8] investigated both the single and binary adsorption/desorption equilibrium and dynamics of lactoferrin and lactoperoxidase, purified from raw whey solutions, using three dif- ferent Sepharose cation-exchangers. Carrere et al. [9] studied the recovery of -lactalbumin (ALA) and -lactoglobulin (BLG) from sweet whey protein by a fluidized ion exchange chromatographic process. They lumped both components as one entity in the pore- diffusion adsorption model as well as in a subsequent lumped kinetic elution model. Conrado et al. [10] described, by means of the pore-diffusion model, the operating parameters related to the use of a hydrophobic resin (Streamline Phenyl) for the recovery of -lactalbumin from cow’s milk whey using expanded-bed adsorp- tion. In a preceding series of publications [11–14], we have managed to develop a method for isolating and separating the two major pro- teins, -lactalbumin and -lactoglobulin, from whey. The method is chromatographic and is based on selective adsorption of the two proteins in cationic forms to the cation-exchanger SP Sepharose FF. 1369-703X/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.bej.2009.12.017