Tunable recombinant protein expression in E. coli: enabler for continuous processing?

Lukas Marschall,Christoph Herwig,Patrick Sagmeister

doi:10.1007/s00253-016-7550-4

Abstract

Tuning of transcription is a powerful process technological tool for efficient recombinant protein production in Escherichia coli. Many challenges such as product toxicity, formation of inclusion bodies, cell death, and metabolic burden are associated with non-suitable (too high or too low) levels of recombinant protein expression. Tunable expression systems allow adjusting the recombinant protein expression using process technological means. This enables to exploit the cell’s metabolic capacities to a maximum. Within this article, we review genetic and process technological aspects of tunable expression systems in E. coli, providing a roadmap for the industrial exploitation of the reviewed technologies. We attempt to differentiate the term “expression tuning” from its inflationary use by providing a concise definition and highlight interesting fields of application for this versatile new technology. Dependent on the type of inducer (metabolizable or non-metabolizable), different process strategies are required in order to achieve tuning. To fully profit from the benefits of tunable systems, an independent control of growth rate and expression rate is indispensable. Being able to tackle problems such as long-term culture stability and constant product quality expression tuning is a promising enabler for continuous processing in biopharmaceutical production.

Highlights

The relevance of the gram-negative bacterium Escherichia coli for the basic biotechnological research as well as for industrial exploitation is outstanding
This is reflected by the fact that 29 % of all biopharmaceutical products approved as biopharmaceuticals between 2010 and July 2014 are produced in E. coli (Walsh 2014)
Expression tuning an opportunity for process development and scientific progress Combined with process technology, tunable expression systems enable the control of the recombinant protein expression

Summary

Introduction

The relevance of the gram-negative bacterium Escherichia coli for the basic biotechnological research as well as for industrial exploitation is outstanding. The recombinant protein expression can be tuned by adjusting the uptake rate of the inducing substrate. One-point addition of varying non-metabolizable inducer concentrations is the most commonly applied method to achieve expression tuning (Khlebnikov et al 2002; Lee and Keasling 2005; Wagner et al 2008).

Results

Conclusion