COMPARISON OF ANION-EXCHANGE AND HYDROXYAPATITE DISPLACEMENT CHROMATOGRAPHY FOR THE ISOLATION OF WHEY PROTEINS

In displacement chromatography, several substances may be isolated and concomitantly concentrated, which makes this separation procedure att ractive for the processing of diluted product streams containing a num ber of high value substances. Here, the suitability of anion-exchange and hydroxyapatite displacement chromatography for the processing of t echnical dairy whey is investigated. The pH and flow-rate of the carri er, the displacer chemistry and, in case of the apatite, the particle diameter of the stationary phase are considered. As a consequence of t he pH sensitivity of the beta-lactoglobulin, one major whey component, apatite displacement chromatography is less then successful in whey s eparation. At a denaturing carrier pH (>8.5) the beta-lactoglobulin zo ne is broad and stretches over the entire displacement train. At a low er carrier pH, previously successful polyanionic displacers do not bri ng about separation, while low-molecular-mass ones do, but they tend t o overrun and thus contaminate the protein zones. In the case of anion -exchange displacement chromatography, polyanions, especially polyacry lic acid (PAA, M(r) 6000), constitute suitable displacers. Here too, a carrier pH of 8.0 is most suited to the separation of the whey protei ns. The low-molecular mass-displacer iminodiacetic acid (IDA, M(r) 133 .4), on the other hand, displaces only a-lactalbumin. The beta-lactogl obulin remains on the column. PAA is used as the displacer to process a dairy whey sample.