Downstream Processing of Plant-Derived Biopharmaceuticals

The extraction and purification of proteins from organisms or biological tissue can be a laborious and expensive process, and often represents the principal reason why vaccines and other therapeutic agents reach costs that become unattainable for many. Downstream processing also can be a major obstacle with respect to cost for large-scale protein manufacturing in plants. However, purification from plant tissues, while still costly, is in general less expensive than purification from their mammalian and bacterial counterparts. Indeed, some plant-derived biopharmaceuticals, such as topically applied monoclonal antibodies, may require only partial purification and thus be even less intensive in terms of labor and cost. 

Purification of a recombinant therapeutic protein from cell culture may involve a few simple steps. For example, affinity chromatography may be used to concentrate the protein. This can be followed with an ion-exchange step and gel filtration. 

A number of purification strategies are in place that have been tailored for specific proteins derived from particular host production platforms. For example, downstream protein extraction from seeds is quite simple 

Release protein from plant material into aqueous environment -wet milling, vacuum filtration, centrifugation 

FIGURE 6.1 Common steps required from the harvest of the crop to the acquisition of purified protein. 

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