Design of Biomolecules For Downstream Processing

There is much interest in how high-value biological products, and particularly proteins, can be designed for downstream bioprocessing.
Although it has long been recognised that the properties of a target molecule influence its behaviour and the approaches taken during downstream processing, until relatively recently there has not necessarily been a concerted and integrated approach to link the two together for any particular molecule. This requires designing the molecule for the downstream processing envisaged and integrates the upstream and downstream investigations such that the two processes are seamless.
To date, the design of molecules for downstream processing has largely been limited to the use of affinity tags and fusion proteins for purification. These have been particularly adopted at the small laboratory scale but are often not practical, too costly or potentially have legislative issues associated with them, which have prevented such approaches becoming more widely adopted at large scale. However, the design of molecules to aid in more efficient traditional chromatographic approaches, such that fewer steps and greater yields are achieved, and/or for aiding alternative approaches such as protein crystallisation and aqueous phase partitioning is an attractive proposition. Further, careful design of biomolecules may also be used in the future to prevent or limit aggregation and harmful post-translation modifications occurring (e.g. deamidation) during the expression of the protein of interest in fermenters and while undergoing downstream processing. This area of designing molecules for manufacturability, from expression to formulation, is likely to be one in which there will be much interest and investigation in the coming years and may ultimately dictate the direction that industrial-scale downstream processing follows.