Discontinuous and continuous separation of the monomeric and dimeric forms of human bone morphogenetic protein-2 from renaturation batches

Bone morphogenetic protein-2 (BMP-2) is one of the most interesting of the approximately 14 BMPs which belong to the transforming-growth-factor-beta (TGF-beta) superfamily. BMP-2 induces bone formation and thus plays an important role as a pharmaceutical protein. Recently, rhBMP-2 has been produced in form of inactive inclusion bodies in Escherichia coli. After solubilization and renaturation the biologically active dimeric form of rhBMP-2 can be generated. However, inactive monomers of BMP-2 are also formed during the renaturation process which must be separated from the active dimeric BMP-2. The purpose of this paper is to present: (a) results of an experimental study of a chromatographic separation of the monomeric and dimeric forms; and (b) a concept for a continuous counter-current simulated moving bed (SMB) process. The capacity of heparin as stationary phase was estimated for different salt concentrations in the mobile phase. A simulation study of a three-zone SMB process was performed applying a two step salt gradient. The results reveal the potential of the process for the purification of the dimeric BMP-2.