Stability in continuous cultures of recombinant bacteria: A metabolic approach

Continuous-culture population dynamics of recombinant bacteria are predicted with a structured kinetic model. The instantaneous specific growth rates of the plasmid-bearing and plasmidfree cells are explicitly calculated from their metabolic activities. The resultant growth-rate differential (between plasmid-bearing and plasmid-free cells) is dynamic and changes over the course of a fermentation. Further, the growth-rate differential is a function of dilution rate. We present the experimental determination of model constants governing plasmid replication and foreign protein expression for a host/vector systemE. coli RR1 [pBR329]. For a different experimental system, we estimate the increased polypeptide expression from a DNA insert solely from the instability population dynamics. Stability predictions agree quite well with experimental observations from the literature and our lab.