Depth filtration is widely used in downstream bioprocessing to clarify high-density cell culture harvest. A filter aid, often diatomaceous earth (DE), is one of the three main components of a depth filter, the others being the filter itself and a binder. In addition to physically removing particulates such as cell debris and precipitated proteins, DE has been shown to adsorb bacteria, viruses, and proteins and hence to contribute to impurity clearance. We have measured the adsorption of model and therapeutic proteins on filter aids in order to investigate the nature and mechanism of protein adsorption onto DE. The mechanisms of protein adsorption onto DE are explored by correlating adsorption data to bulk measured properties such as composition, morphology, surface area and surface charge density/zeta potential. Our findings show that despite its heterogeneous character, DE consistently performs as a cation exchanger, with capacity determined by the distinctive structural properties of DE relative to those of a typical commercial resin. These fundamental measurements can be leveraged in the optimal design and usage of depth filtration in downstream purification.

Adsorptive properties of filter aids

253rd National Meeting (2017)

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