Continuous removal of protein aggregates by annular chromatography

The removal of polymeric proteins from their monomers is a frequently encountered separation task, especially in the polishing step of therapeutic proteins. Continuous separation of protein polymers from monomers by annular chromatography using size exclusion chromatography has been studied regarding the resolution, recovery, fouling, and productivity and has been compared to conventional chromatography. An IgG preparation rich in aggregates was used as a model protein mixture. Under conditions that maximized the throughput, the polymers could be separated from the monomers, but baseline separation could not be achieved. Baseline separation was also not possible in batch mode using equivalent conditions, which was also confirmed by computer simulation. For separation of the aggregates from the product the entire available separation space (360 degrees) was indispensable. Therefore only cyclic, discontinuous regeneration could be carried out. Loading was identified as a critical step, since the concentrated protein solution evaded into the headspace instead of migrating into the gel where viscous fingering often occurs in conventional chromatography. The productivity of annular chromatography was two times higher than that of the conventional batch chromatography, and the buffer consumption was reduced to half the conventional value. These two benefits are especially important for protein separation processes that suffer from low loadability, such as size exclusion chromatography. We have demonstrated that size exclusion can be performed on an industrial scale when it is run continuously with the aid of a pressurized annular chromatograph.