Expanded bed adsorption process for protein recovery from whole mammalian cell culture broth.

An expanded bed process for the recovery of soluble protein from whole mammalian cell culture broth by adsorption on specially-designed cation exchange resin is described. A bed of large, dense resin particles in a 5 cm ID column was expanded 2.45 times by the upward flow of three-fold dilute broth. The void space was sufficient to permit cells to flow through the column as the protein was adsorbed. The liquid flow in the column was distributed to minimize back-mixing and create a multiplate adsorption process. During elution, the liquid flow was reversed and the resin bed was packed. In contrast to conventional filtration, the expanded bed process combines clarification, product recovery and concentration into a single-step process. Residence time distribution analysis showed a small degree of axial dispersion and the generation of 22 theoretical plates in the expanded bed (170 ml resin with an unexpanded height of 8.6 cm). Two pilot runs of the process were done with 26 and 36 liters of whole broth at a linear velocity of 135 cm h-1. More than 95% adsorption of the antibody product was achieved without breakthrough in a single pass through the column. Elution recovered 70-85% of the antibody at a concentration as much as 39 times higher than in the broth. The antibody was purified seven-fold in the recovery process mainly because adsorption conditions prevented the binding of 80% of the undesired protein. Because it is less labor-intensive, the expanded bed process is potentially more economical than the filtration recovery process. Although processing time with the expanded bed is considerable, it does not require constant monitoring as does filtration.