Advancements in Inducer Systems for Recombinant Protein Production in E. coli

Escherichia coli (E. coli) is the predominant industrial microorganism and cost-effective microbial cell “factory” for producing commercial products, such as metabolites, enzymes, biochemicals, and high-value biotherapeutics. It is the primary workhorse for non-glycosylated recombinant proteins production as it is the production organism used to produce around 30% of biopharmaceutical products. Heterologous protein expression in E. coli is often a preferred choice for many reasons: it is economical, provides a fast growth rate, and can reach high cell density and high product titers. Being widely studied, an abundance of biochemical and physiological knowledge is also available. Also, various genetic tools are available to manipulate E. coli, including a significantly extensive catalog of expression plasmids and engineered strains and several cultivation strategies. Selecting appropriate expression plasmids and promoter strength is crucial for efficient protein production. Promoter strength depends on the promoter components that can be either constitutive or inducible. Constitutive promoters allow continuous gene expression, which can cause a metabolic burden affecting cell growth, whereas inducible promoters control gene expression through specific inducers. The existing expression systems are diverse and complex, and its selection depends on the nature of target protein that requires in particular cases to be produced at high concentrations, or at different cell growth phases, or at particular location whether in the cytoplasmic or periplasmic space or in some cases, secretion into medium.