Effect of specific production rate of recombinant protein on multimerization of plasmid vector and gene expression level

In fed-batch cultures of recombinant Escherichia coli BL21(DE3)[pT7-G3IL2] at high cell concentration, the post-induction specific growth rate was carefully regulated by controlled medium feed to maximize the synthesis level of recombinant fusion interleukin-2, G3.IL-2. A maximum concentration of G3.IL-2 (11.25 g l^-1) was achieved in the induced recombinant culture growing at the rate of 0.056 h^-1. A steep decrease in the expression level of G3.IL-2 was observed at the post-induction specific growth rates higher than its optimal value (0.056 h^-1). In the induced recombinant cultures, plasmid multimerization was observed and highly dependent on specific growth and production rate: a higher post-induction specific growth rate and an increased specific production rate tended to significantly promote it much further. Moreover, plasmid stability was found to decrease rapidly in a faster growing culture. Copyright (C) 1999 Federation of European Microbiological Societies.