Harnessing Candida tenuis and Pichia stipitis in whole‐cell bioreductions of o‐chloroacetophenone: Stereoselectivity, cell activity, in situ substrate supply and product removal

The analysis of host cell proteins (HCPs) is one of the most important analytical requirements during bioprocess development of therapeutic moieties. In this review, we focus on the comparison of different methods for the analysis of HCPs and how cell lines, fermentation conditions, and unit operations influence HCP distribution during the process chain. Current guidelines typically require reduction of HCPs to the ppm level, depending on the intended use, the route of administration of the product, and the production system. A range of immunospecific and non‐specific methods are available that have been globally accepted by regulatory bodies. Immunospecific methods, such as ELISA, are simple to use in routine analysis and can quantify low levels of HCPs when specific antibodies are available. Non‐specific methods are more complex; however, they provide a holistic view of the HCP profile and qualitative information of the composition of HCP in the sample. Different methods for the comparison of bioprocessing strategies during scale‐up and purification development are compared herein. The methods include immunospecific methods, such as ELISA, western blot, and threshold, and non‐specific methods, such as 2D‐DIGE and 2D‐HPLC combined with MS.