Factors influencing excretive production of human epidermal growth factor (hEGF) with recombinant Escherichia coli K12 system

Human epidermal growth factor (hEGF) was expressed and excreted into cultur e medium in an excretory recombinant Escherichia coli system. Conditions fo r the production of hEGF in this system were investigated. Results showed t hat the slight reduction of promoter strength improved the stability of pla smid and the production of hEGF in this recombinant system. One favorable M MBL medium for hEGF production was formulated by evaluating the effects of medium components, ampicilin addition and pH. hEGF production was affected obviously by culture conditions, especially fermentation temperature. High temperature (32 degreesC) was very beneficial for culture process by increa sing productivity and reducing the quantity of isopropyl-beta -D-thiogalact opyranoside (IPTG) for sufficient induction. High cell density and hEGF pro ductivity could be accomplished concomitantly by inducing the culture at mi ddle or late log phase of cell growth. In comparison with the batch process , fed-batch cultivation could improve plasmid stability from ca. 72% to ca. 83%, and increased hEGF productivity by 24.4%. Under all these circumstanc es, almost all expressed hEGF (greater than or equal to 95%) was fully excr eted into the culture medium.