Effect of glucose on the expression parameters of recombinant protein in Escherichia coli during batch growth in complex medium.

The expression parameters were determined at different phases of batch growth of Escherichia coli JM101/pYEJ001 in complex medium and at different conditions of glucose addition. Thus the plasmid content, the RNA content, the RNA synthesis rate, the specific recombinant mRNA content, the specific recombinant mRNA synthesis rate, the recombinant chloramphenicol acetyltransferase content, and the overall protein synthesis rate were determined during growth with no glucose, with initial glucose, with glucose feeding during stationary phase, and with initial glucose plus glucose feeding during stationary phase. The results show that the specific rate of total RNA synthesis was enhanced in the presence of glucose at both exponential and stationary phases, while recombinant mRNA synthesis was enhanced only at stationary phase by glucose feeding. However, the steady-state level of the recombinant mRNA was not changed under the same conditions. In addition, although the overall protein synthesis rate at exponential phase was enhanced in the presence of glucose, the specific recombinant protein level was unaffected. The specific synthesis rate of recombinant mRNA varied inversely with the plasmid content during exponential and stationary phases. Furthermore, changes in the specific activity of the recombinant protein were not correlated with either the changes in the specific synthesis rate of the recombinant mRNA or the overall protein synthesis rate. Therefore, the specific activity of the recombinant protein is not universally limited by its gene transcription rate or the overall protein synthesis capacity.