E.coli is one of the most widely used and well-studied expression systems. This system is excellent for expression of functional non-glycosylated proteins, since the production of glycosylated proteins require a Golgi apparatus, which E. coli cells do not possess. Bacteria did not develop a sophisticated mechanism for performing posttranslational modifications.

Advantages of E.coli as an expression system.

  • Rapid expression
  • High yield
  • Ease of culture and genome modification
  • Inexpensive
  • Mass production is fast and cost-effective

Disadvantages of E.coli as an expression system.

  • Protein with disulfide bonds is difficult to express
  • Produces unglycosylated proteins
  • Protein produced with endotoxin
  • Acetate formation resulting in cell toxicity
  • Protein produced as inactive inclusion bodies that require refolding

Expression system starts with inserting recombined plasmid into bacteria cell and producing starter culture. Growing bacteria protein expression is induced with IPTG. Grown bacterial pellet is collected using centrifugation and resuspended in lysis buffer. Then, bacterial cells are lysed through sonification and obtained proteins in supernatant are purified by chromatography.

Figure 1. Bacteria expression system.