Robust aggregate separation by Sartobind Rapid A Protein A membrane

Protein A resins are the most widely used affinity media for product capture in antibody and Fc-fusion protein purification. However, they generally lack the capability to separate monomers from co-binding aggregates. Recently, Protein A membrane has emerged as a promising alternative to resin-based Protein A column. We previously demonstrated that Sartobind Rapid A, a Protein A membrane from Sartorius, shows much stronger aggregate separation capability than resin-based Protein A columns. In the current work, using an aggregate-rich culture harvest as feed material, we evaluated three mobile phase additives (i.e., NaCl, CaCl₂ and Arg·HCl) for their effects on monomer-aggregate separation by Sartobind Rapid A membrane. After identifying the conditions that provided the best resolution, we challenged Sartobind Rapid A membrane with four artificial samples containing different ratios (i.e., 15%, 30%, 45% and 60%) of aggregates. Analysis of the main elution peak portion by size-exclusion chromatography-high performance liquid chromatography (SEC-HPLC) suggested that this Protein A membrane effectively removed most aggregates in all artificial samples regardless of the percentage of aggregates in them. Thus, the current study shows that aggregate separation by Sartobind Rapid A membrane is not only effective but also highly robust, which makes Protein A membrane a more attractive choice than Protein A column for product capture, especially for cases where the culture harvest contains high amounts of aggregates.