A comprehensive study of glucose and oxygen gradients in a scaled-down model of recombinant HuGM-CSF production in thermoinduced <i>Escherichia coli</i> fed-batch cultures

The effect of gradients of elevated glucose and low dissolved oxygen in the addition zone of fed-batch <i>E. coli</i> thermoinduced recombinant high cell density cultures can be evaluated through two-compartment scale-down models. Here, glucose was fed in the inlet of a plug flow bioreactor (PFB) connected to a stirred tank bioreactor (STB). <i>E. coli</i> cells diminished growth from 48.2 ± 2.2 g/L in the stage of RP production if compared to control (STB) with STB-PFB experiments, when residence time inside the PFB was 25 s (34.1 ± 3.5 g/L) and 40 s (25.6 ± 5.1 g/L), respectively. The recombinant granulocyte-macrophage colony-stimulating factor (rHuGM-CSF) production decreased from 34 ± 7% of RP in inclusion bodies (IB) in control cultures to 21 ± 8%, and 7 ± 4% during the thermoinduction production phase when increasing residence time inside the PFB to 25 s and 40 s, respectively. This, along with the accumulation of acetic and formic acid (up to 4 g/L), indicates metabolic redirection of central carbon routes through metabolic flow and mixed acid fermentation. Special care must be taken when producing a recombinant protein in heat-induced <i>E. coli</i>, because the yield and productivity of the protein decreases as the size of the bioreactors increases, especially if they are carried at high cell density. Thermoinduced recombinant <i>E. coli</i> grew less in a two-compartment scale-down model.Heat-inducible <i>E. coli</i> cultures at a large scale significantly decrease recombinant protein production.The accumulation of acetic and formic acid increases when <i>E. coli</i> is exposed to glucose and oxygen gradients.The axial flow pattern inside the PFB mimics glucose and dissolved oxygen gradients at the industrial scale. Thermoinduced recombinant <i>E. coli</i> grew less in a two-compartment scale-down model. Heat-inducible <i>E. coli</i> cultures at a large scale significantly decrease recombinant protein production. The accumulation of acetic and formic acid increases when <i>E. coli</i> is exposed to glucose and oxygen gradients. The axial flow pattern inside the PFB mimics glucose and dissolved oxygen gradients at the industrial scale.