FED-BATCH OPERATION OF RECOMBINANT ESCHERICHIA-COLI CONTAINING TRP PROMOTER WITH CONTROLLED SPECIFIC GROWTH-RATE

A feb-batch operation for the production of bovine somatotropin (bST) under the control of tryptophan promoter in Escherichia coli was inves tigated. The plasmid used contains a two-cistron system and altered co don usage for higher expression of bST. Specific growth rate is an imp ortant parameter in the fermentation, because it affects the productio n of growth-inhibitory organic acids and the expression of recombinant protein. The feeding rate was adjusted to keep the specific growth ra te constant in this study. The variable growth yield expressed as a fu nction of time was used for the calculation of the feeding rate. The g rowth yield decreases during the fermentation as product expression is induced. The specific growth rate was well controlled; however, intra cellular bST concentration decreased at high cell concentrations. This is considered to be due to degradation by proteases. The decrease was prevented by an exponential feeding of the yeast extract as an organi c nitrogen source. (C) 1994 John Wiley & Sons, Inc.