High-throughput process development for recombinant protein purification

Abstract

Methods development in chromatographic purification processes is a complex operation and has traditionally relied on trial and error approaches. The availability of a large number of commercial media, choice of different modes of chromatography, and diverse operating conditions contribute to the challenging task of accelerating methods development. In this paper, we describe a novel microtiter-plate based screening method to identify the appropriate sequence of chromatographic steps that result in high purities of bioproducts from their respective culture broths. Protein mixtures containing the bioproduct were loaded on aliquots of different chromatographic media in microtiter plates. Serial step elution of the proteins, in concert with bioproduct-specific assays, resulted in the identification of "active fractions" containing the bioproduct. The identification of a successful chromatographic step was based on the purity of the active fractions, which were then pooled and used as starting material for screening the next chromatographic dimension. This procedure was repeated across subsequent dimensions until single band purities of the protein were obtained. The sequence of chromatographic steps and the corresponding operating conditions identified from the screen were validated under scaled-up conditions. Various modes of chromatography including hydrophobic interaction, ion exchange (cation and anion exchange) and hydrophobic charge-induction chromatography (HCIC), and different operating conditions (pH, salt concentration and type, etc.) were employed in the screen. This approach was employed to determine the sequence of chromatographic steps for the purification of recombinant alpha-amylase from its cell-free culture broth. Recommendations from the screen resulted in single-band purity of the protein under scaled-up conditions. Similar results were observed for an scFv-beta-lactamase fusion protein. The use of a miniaturized screen enables the parallel screening of a wide variety of actual bioprocess media and conditions and represents a novel paradigm approach for the high-throughput process development of recombinant proteins.