In recent years, fluidized-bed adsorption has been used as an alternative method to conventional packed-bed column chromatography for protein purification (1–8). This technology allows the recovery of high-value recombinant proteins and other biomolecules straight from unclarified crude feed stocks, such as cell culture media, fermentation broths, and cell extracts, among others. In a protein purification system utilizing fluidized-bed adsorption, clarification, purification, and concentration are performed in a single step. The differences between packed-bed and fluidized-bed column operations are illustrated in Fig. 1. Particulate matter from unclarified feed stocks may get trapped between gel particles causing clogging of the packed-bed column. Another potential problem, which is illustrated in Fig. 1A, is cell debris forming a cake at the column inlet, limiting the passage of fluid through the column bed. In contrast, liquid flow in a fluidized bed is upward and the resulting force causes the bed to expand, making spaces between adsorbent particles. The loosely suspended adsorbent particles shown in Fig. 1B allow the unimpeded passage of fluids through the column bed.