Economic and ecological benefits of a leaky E. coli strain for downstream processing: a case study for staphylococcal protein A

BACKGROUND Downstream processing of soluble recombinant proteins from Escherichia coli is complicated by the need to access the intracellular product by cell disruption and to separate the target protein from impurities, particularly host cell protein, DNA, endotoxins and lipids. We previously demonstrated the ability of the E. coli X‐press strain to leak high amounts of product to the culture medium without sacrificing viability. In this case study, we assessed the economic and ecological benefit of this strain for downstream processing in direct comparison to the industrial standard E. coli BL21(DE3). Staphylococcal Protein A was used as a model protein. We performed recombinant protein production, primary recovery and capture by anion exchange chromatography at laboratory scale, and used the data obtained for estimating costs and resource consumption by economic modeling. RESULTS After primary recovery, the X‐press process resulted in a 1.5‐fold higher product purity, a 150‐fold lower DNA, 3.5‐fold lower endotoxin and 3.4‐fold lower lipid load compared to BL21(DE3). Consequently, anion exchanger binding capacity was increased 2.7‐fold and purity and concentration of the eluate also was increased. Extracellular protein production with X‐press resulted in a 25% reduction of costs and a 36% reduction of both water usage and water‐related CO 2 emissions compared to intracellular production with BL21(DE3). CONCLUSIONS This case study performed with stapyhlococcal Protein A demonstrated the potential of E. coli X‐press to reduce costs for downstream processing and improve the environmental footprint by simplified primary recovery, lower impurity load and consequently higher chromatographic efficiency. © 2021 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.