Scale-up process for expression and renaturation of recombinant human epidermal growth factor from Escherichia coli inclusion bodies

Abstract

A cDNA encoding mature epidermal growth factor (EGF) was isolated and cloned into a pQE30 vector in which the His6‐tagged EGF was expressed. pH‐stat feeding of concentrated medium at the time of isopropyl β‐d‐thiogalactoside induction and slug‐feedings of the enriched medium during the induction resulted in a higher cell density and specific expression. Using a simple refolding protocol that consisted of 1 mM l‐cysteine addition for a 1‐h reduction followed by 5 mM l‐cystine addition for oxidative refolding, we were able to convert nearly all EGF monomers into the oxidized form. Also, the refolding aggregate was converted into the monomeric form. Approx. 50% overall yield was obtained from the dissolved inclusion bodies to a single peak under FPLC. We hope that the result of this study may provide information that is useful for the scale‐up of the recombinant human EGF production process.