Enzyme Production in Escherichia coli

Abstract

With the development of recombinant DNA technology, industrial enzymes are increasingly being produced in heterologous hosts, particularly in the bacterium Escherichia coli and the yeasts Saccharomyces cerevisiae and Pichia pastoris. Although mammalian cells are predominately used for the production of recombinant human enzymes, this chapter focuses on the use of E. coli as an alternative host for the production of recombinant enzymes. In designing the fermentation process, the preferred method is the use of high-cell-density fermentations in stirred-tank reactors. Many bacterial promoters also contain an operator that interacts with a cognate transcription factor. Because the number of gene transcripts is the strongest determinant of high-level protein production, transcriptional regulation is the most important consideration when developing protein production methods. Protein secretion to the periplasm, in contrast, has been used extensively to produce functional proteins, obtain authentic protein sequences, increase yields, and facilitate protein purification. It is known that the fine-tuning of gene expression rates is necessary to obtain increased secretion efficiency, because highly expressed proteins tend to overwhelm the secretion machinery, resulting in the formation of inclusion bodies. Inducible gene expression systems are commonly used in recombinant protein production. A strategy to implement autoinduction is based on the bacterial quorum-sensing mechanism. Limiting essential nutrient levels, and therefore cell growth rates, is an effective strategy to reduce acetate production. On the production side, achieving a balance between protein production levels and the metabolic burden on the cell is a time-consuming process.