GROWTH KINETICS AND HUMAN GROWTH HORMONE PRODUCTION OF A HEAT- INDUCIBLE RECOMBINANTE CHERICHIA COLI DURING BATCH FERMENTATION

The batch fermentation production of human growth hormone (hGH) was studied in a new recombinant Escherichia coli. The effect of different levels of dissolved oxygen and glucose concentration on cell density and substrate utilization were evaluated. The results indicated that the optimum level of dissolved oxygen was 25% of air saturation. The specific growth rate reached a maximum for an optimal glucose concentration of 5 gl-1, the maximum yield was 0.58 gg-1 and glucose was completely consumed after 10 hrs. The growth of recombinant E. coli on semi-defined and complex media was compared. The results demonstrated that dry cell weight and maximum specific growth rate were 2.35 gl-1 and 0.4 h-1 on a complex medium, respectively, but they were 3.3 gl-1 and 0.24 h-1 on semi-defined medium. The plasmid stability and hGH production during batch fermentation were investigated. The results suggested that the specific growth rate is the most important factor on hGH production and should be investigated in fed batch cultivation to get high cell density.