Influences of yeast extract on specific cellular yield of Ovine growth hormone during fed-batch fermentation of E-coli

In most cases of E. coli high cell density fermentation process, maximizing cell concentration helps in increasing the volumetric productivity of reco mbinant proteins usually at the cost of lower specific cellular protein yie ld. In this report, we describe a process for maintaining the specific cell ular yield of Ovine growth hormone (oGH) from E, coli by optimal feeding of yeast extract during high cell density fermentation process. Recombinant o GH was produced as inclusion bodies in Escherichia coli. Specific cellular yield of recombinant oGH was maintained by feeding yeast extract along with glucose during fed-batch fermentation. Glucose to yeast extract ratio of 0 .75 was found to be optimum for maintaining the specific cellular oGH yield of 66 mg/g of E, coli cells. Continuous feeding of yeast extract along wit h glucose helped in reducing acetic acid secretion and promoted higher cell growth during fed-batch fermentation. High cell growth of E. coli and high specific yield of recombinant oGH thus helped in achieving high volumetric productivity of the expressed protein. A maximum of 2 g/l of ovine growth hormone was expressed as inclusion bodies in 12 h of fed-batch fermentation .