Towards implementation of novel single-use devices in integrated processes for biopharmaceuticals

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Pseudo-affinity capture of <i>K. phaffii </i>host cell proteins in flow-through mode: purification of protein therapeutics and proteomic study

K. phaffii is a versatile expression system that is increasingly utilized to produce biological therapeutics – including enzymes, engineered antibodies, and gene-editing tools – that feature multiple subunits and complex post-translational modifications. Two major roadblocks limit the adoption of K. phaffii in industrial biomanufacturing: its proteome, while known, has not been linked to downstream process operations and detailed knowledge is missing on problematic host cell proteins (HCPs) that endanger patient safety or product stability. Furthermore, the purification toolbox has not evolved beyond the capture of monospecific antibodies, and few solutions are available for engineered antibody fragments and other protein therapeutics. To unlock the potential of yeast-based biopharmaceutical manufacturing, this study presents the development and performance validation of a novel adsorbent – PichiaGuard – functionalized with peptide ligands that target the whole spectrum of K. phaffii HCPs and designed for protein purification in flow-through mode. The PichiaGuard adsorbent features high HCP binding capacity (∼25 g per liter of resin) and successfully purified a monoclonal antibody and an ScFv fragment from clarified K. phaffii harvests, affording &gt;300-fold removal of HCPs and high product yields (70 – 80%). Notably, PichiaGuard outperformed commercial ion exchange and mixed-mode resins without salt gradients or optimization in removing high-risk HCPs – including aspartic proteases, ribosomal subunits, and other peptidases – thus demonstrating its value in modern biopharmaceutical processing

Novel multimodal cation-exchange membrane for the purification of a single-chain variable fragment from <i>Pichia pastoris</i> supernatant

A novel salt-tolerant cation-exchange membrane, prepared with a multimodal ligand, 2-mercaptopyridine-3-carboxylic acid (MMC-MPCA), was examined for its purification properties in a bind-and-elute mode from the high conductivity supernatant of a Pichia pastoris fermentation producing and secreting a single-chain variable fragment (scFv). If successful, this approach would eliminate the need for a buffer exchange prior to product capture by ion-exchange. Two fed-batch fermentations of Pichia pastoris resulted in fermentation supernatants reaching an scFv titer of 395.0 mg/L and 555.7 mg/L, both with a purity of approximately 83%. The MMC-MPCA membrane performance was characterized in terms of pH, residence time (RT), scFv load, and scFv concentration to identify the resulting dynamic binding capacity (DBC), yield, and purity achieved under optimal conditions. The MMC-MPCA membrane exhibited the highest DBC of 39.06 mg/mL at pH 5.5, with a residence time of 1 minute, while reducing the pH below 5.0 resulted in a significant decrease of the DBC to around 2.5 mg/mL. With almost no diffusional limitations, reducing the RT from 2 to 0.2 min did not negatively impact the DBC of the MMC-MPCA membrane, resulting in a significant improvement in productivity of up to 180 mg/mL/min at 0.2 min RT. Membrane fouling was observed when reusing the membranes at 0.2 and 0.5 min RT, likely due to the enhanced adsorption of impurities on the membrane. Changing the amount of scFv loaded onto the membrane column did not show any changes in yield, instead a 10-20% loss of scFv was observed, which suggested that some of the produced scFv were fragmented or had aggregated. When performing the purification under the optimized conditions, the resulting purity of the product improved from 83% to approximately 92-95%