Kinetics of inclusion body production in batch and high cell density fed-batch culture of Escherichia coli expressing ovine growth hormone

A process for maximizing the volumetric productivity of recombinant ovine g rowth hormone (r-oGH) expressed in Escherichia coli during high cell densit y fermentation process has been devised. Kinetics of r-oGH expression as in clusion bodies and its effect on specific growth rates of E. coli cells wer e monitored during batch fermentation process. It was observed that during r-oGH expression in E. coli, the specific growth rate of the culture became an intrinsic property of the cells which reduced in a programmed manner up on induction. Nutrient feeding during protein expression phase of the fed-b atch process was designed according to the reduction in specific growth rat e of the culture. By feeding yeast extract along with glucose during fed-ba tch operation, high cell growth with very little accumulation of acetic aci d was observed. Use of yeast extract helped in maintaining high specific ce llular protein yield which resulted in high volumetric productivity of r-oG H. In 16 h of fed-batch fermentation, 3.2 g l(-1) of r-oGH were produced at a cell OD of 124. This is the highest concentration of r-oGH reported to d ate using E. coli expression system. The volumetric productivity of r-oGH w as 0.2 g l(-1) h(-1), which is also the highest value reported for any ther apeutic protein using IPTG inducible expression system in a single stage fe d-batch process. (C) 1999 Elsevier Science B.V. All rights reserved.