Engineering of Escherichia coli to improve the purification of periplasmic Fab' fragments: changing the pI of the chromosomally encoded PhoS/PstS protein.

Escherichia coli is a widely used host for the heterologous expression of proteins of therapeutic and commercial interest. The scale and speed at which it can be cultured can result in the rapid generation of large quantities of product. However, to achieve low costs of production a simple and robust purification process is also required.

A plasmid system for optimization of Fab' production in Escherichia coli: importance of balance of heavy chain and light chain synthesis.

We demonstrate the importance of optimizing the balance of light chain (LC) and heavy chain (HC) expression to achieve high level production of Fab' fragments in the Escherichia coli periplasm. The LC:HC balance has been controlled by varying the codon usage of the signal peptide (SP) and 5' mature domain coding regions. Different SP coding regions have been identified from a codon wobble-based library using alkaline phosphatase (AP) as a reporter gene.