The influence of matrix properties and op-initial purification are combined in this unit operation, erating conditions on the performance in fluidized-bed resulting in shortened overall processing time and inadsorption has been studied using Streamline diethylcreased overall product yield. Several applications of aminoethyl (DEAE), an ion exchange matrix based on fluidized-bed adsorption starting from various culture quartz-weighted agarose, and bovine serum albumin broths or homogenates have been described up to now (BSA) as a model protein. Three different particle size (Barnfield-Frej et al., 1994; Batt et al., 1995; Belter et fractions (120-160 m, 120-300 m, and 250-300 m) were investigated. Dispersion in the liquid phase was al., 1973; Chang and Chase, 1996a; Erickson et al., 1994; reduced when particles with a wide size distribution were Tho ¨mmes et al., 1995a), but investifluidized compared to narrow particle size distributions.
gations on the parameters governing the performance When the mean particle diameter was reduced, the breakof this technology still are scarce.
through capacities during frontal adsorption were en-Generally the adsorption performance in chromatolarged due to a shorter diffusion path length within the graphic processes is influenced by mass transport effects, matrix. At small particle diameters the effect of film mass transfer became more relevant to the adsorption perforadsorption kinetics, and dispersion, which depend mance in comparison to larger particles. Therefore matrimainly on matrix properties and operating parameters.
ces designed for fluidized-bed adsorption should have
As protein purification using porous adsorbent particles small particle diameter and increased mean particle denis mainly a transport-limited operation, investigations sity to ensure small diffusion path length in the particle concentrated on the question, if the basic system and a high interstitial velocity to improve film mass transfer. Studies on the influence of sedimented matrix height parameters governing protein sorption in packed beds on axial mixing showed an increased Bodenstein number are also dominating this process in fluidized-bed adsorpwith increasing bed length. Higher breakthrough capacittion.
ies were also found for longer adsorbent beds due to Chase and collaborators gathered very important data reduced dispersion and improved fluid and particle side on protein adsorption to fluidized agarose adsorbents mass transfer. With increasing bed height the influence originally fabricated for packed beds. Investigations on of flow rate on breakthrough capacity was reduced. For a settled bed height of 50 cm breakthrough capacities of mass transport (Chase and Draeger, 1992a), axial mixing 80% of the equilibrium capacity for flow rates varying (Draeger and Chase, 1990), and the influence of biomass from 3 to 9 cm/min could be achieved.