Downstream processing refers to the processes that take place after fermentation to recover and purify the product. Following cell culture, recovery is carried out by centrifugation and filtration from which the resulting cell harvest is transferred to the low-productivity purification processes. Purification of biologics involves usually Protein-A affinity chromatography, ion exchange chromatography and further filtration. Protein-A affinity chromatography is the most widely used method for capturing immunoglobin when purifying antibodies. However, productivity using this method is limited by the slow flow rates of resin columns. The price of Protein A resins contributes to the high prices being paid for by patients for biologics as it can cost up to €14,000/L (Franzreb M et al. ,). In trying to match the productivity of the upstream processes, the resulting Protein-A resin columns are oversized to increase the volumetric flow rate. This requires large investment in larger columns, larger facilities and associated equipment.
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Further polishing steps such as anion and cation exchange chromatography are also used to purify the antibodies. These long, complicated processes result in non-optimal yields and increased risk of lost batches due to contamination or operator error. Sophisticated SU technologies such as perfusion bioreactors are pushing productivities that are more than 25 × higher than batch culture (Wang L et al. ,). This has resulted in downstream processes struggling to keep up with the increased workload which has led the biopharmaceutical industry to seek new technologies to take advantage of the increased output in upstream processes.
Disposable technologies for downstream processing
Technology such as Disposable membrane chromatography has demonstrated an ability to match the high bioreactor output from upstream processes and act as alternative to traditional polishing steps such as anion exchange chromatography and Protein-A affinity chromatography, especially for monoclonal antibody purification. It offers high yield and > 99% purity in a one-step purification process with much faster flow rates than Protein A resin columns (Hou Y et al. ,). Replacing Anion Exchange column chromatography with Anion Exchange membrane chromatography has resulted in similarly high viral clearance at a much higher flow rate and load density (Arunakumari A et al. ,) As the membrane chromatography columns are single-use, it eliminates the risk of cross-contamination batches if numerous products were being run in a single plant. The convective mode of mass transport enables the use of a membrane chromatography adsorber that is significantly smaller in size than a conventional ion-exchange resin column.
The smaller membrane chromatography device provides product of the same quality while reducing floor space requirements, hardware equipment, processing time, and labour use. A buffer saving of 95% was observed when membrane chromatography was compared to traditional column chromatography, regardless of the production scale (Zhou J, et al. ,). The stainless-steel chromatography column requires cleaning and storage steps, whereas the disposable nature of the membrane technology has reduced water and buffer usage by 95% because there are no CIP or SIP procedures required. A study was conducted to compare the environmental footprint of a traditional biopharmaceutical manufacturing facility using fixed-in-place stainless steel equipment and a facility implementing disposable technologies. The findings of this paper found that overall waste streams were reduced with disposable technologies, specifically with regard to water load and labour hours. A 25. 5% reduction in CO2emissions was estimated for the facility using disposables relative to the traditional stainless steel-equipped facility. The reduction in CO2 emission mainly is derived from the reduced usage of water, which more than compensates for the emission of CO2 associated with the use of plastics. (Sinclair, et al. ,)