Adsorbent bead, immobilized affinity

The use of small affinity adsorbent particles immobilized in hydrogel beads has been investigated for whole broth processing (1). The adsorbent particles can contain biospecific ligands covalently attached to a porous solid support. A mathematical model was developed to study bioproduct adsorption using immobilized affinity adsorbent beads in batch operation. 

The performance of immobilized and freely suspended affinity adsorbents was compared by calculating adsorption rates and selectivities for four different bead geometries. Simulation results indicate that the performance of finely ground adsorbent particles immobilized in hydrogel beads is superior compared to freely suspended adsorbents. The mathematical model was further used for simulation studies to investigate the effect of bead design parameters on product adsorption. 

Figure 1 shows a schematic diagram of an immobilized affinity adsorbent bead. Hydrogel, by virtue of its extremely high water content (>90%), offers limited diffusional resistance to the desired product. It is therefore used as an inert matrix to support... 

Figure 1. Schematic diagram of an immobilized affinity adsorbent bead.

In the past, similar bidispersed systems have been investigated and modeled in the catalyst deactivation area (5-7). However, modeling of immobilized affinity adsorbent beads is more complex due to the non-linearity introduced by the rapid ligand binding reaction which is dependent on the product concentration. 

Figure 7 shows the variation of selectivity with respect to time for three types of affinity beads (Cases (a), (b) and (c)). In all three cases, selectivity decreases from the initial maximum value as time progresses. Due to identical diffusivities, the two products have very similar concentration profiles within the immobilized adsorbent bead at initial time. Thus the initial selectivity is just the ratio of their adsorption rate constants. However, since product... 

An obvious extension of the CBM-fusion technology is to enable a single-step purification and immobilization of fusion proteins by generating active CBM-Protein. Moreover, the utilization of the carbohydrate affinity system, such as cellulose, is attractive because it does not require a derivatized matrix, and cellulose is available in a variety of inexpensive forms, such as preformed microporous beads, highly adsorbent sponges or cloth and microcrystalline powders [181]. 

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