Continuous precipitation of antibodies by feeding of solid polyethylene glycol

Abstract

The economic benefits of continuous PEG precipitation of antibodies compared to continuous capture by protein A affinity chromatography have been always lowered by the excess amount of material needed for the process. PEG is added as a concentrated stock solution and therefore liquid handling is increased during this step. To fully exploit the benefits of PEG precipitation, the precipitant must be added in solid form. We used an in-line feeding device with a screw conveyor delivery system for the continuous addition of PEG6000 in a powder form. The powder feeding device was connected to a tubular reactor where the precipitation occurs. Protein precipitation was continuously performed for 4 h. A yield of 76 % and 79 % with a purity of 98 % was achieved. The total cost of goods and the environmental footprint were compared with typical chromatography-based purification methods; batch and continuous periodic countercurrent protein A affinity chromatography with four columns. Solid PEG precipitation showed a remarkable reduction in water consumption and equipment size, reducing production costs by 45 % compared to liquid PEG and 53 % cheaper than Protein A periodic counter-current chromatography. Process mass intensity was reduced by 55 % and carbon emissions by 60 %. The reduction of water by the direct addition of PEG also impacted the environmental footprint and process costs. This is an attractive approach for a continuous capture step yielding an uninterrupted mass flow of the product and will pave the way for PEG precipitation as a capture step.