Downstream processing polishing step

As with any other classical approach in downstream processing of proteins, the process is split into three steps a capture step, followed by a separation step, and finally by a polishing step to remove residual impurities originating from leached compounds of the sorbent and/or fragments and aggregates.72... 

The process of purification, also called downstream processing, depends on the product and the degree of purification required.74 Current strategies used for purification of therapeutic proteins generally involve these steps (1) sample preparation (clarification or extraction), (2) product capture (product concentration), (3) intermediate purification (removal of bulk impurities), and (4) polishing (removal of trace impurities) as shown in Figure 32.4. 

Downstream processing is commonly classified into four distinct steps broth conditioning and removal of insolubles isolation of the desired product (including clarification and extraction) purification with high-resolution techniques and polishing. 

It is clear that this difficult separation task cannot be done with a single chromatographic step. Therefore, the typical downstream process for example, a monoclonal antibody consists of three distinct chromatographic steps capturing -intermediate purification and polishing. 

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