X: Biomass concentration; G: Glucose concentration; A: Acetate concentration; DOT: Dissolved oxygen tension; qO: Specific O2 consumption rate; my: Specific growth rate; F: Feed rate.

Dynamic simulation of an E. coli batch/fedbatch process, started as a batch followed by exponential/constant feed rate. Acetate is produced during the batch phase. Therefore the initial glucose concentration should be so low that  it is exhausted before the acetate concentration becomes too high. But then the biomass concentration is low. To further increase the biomass concentration, an exponential feed was started with an exponent (0.32 /h resulting in the same spec. growth rate) which prevents overflow metabolism. The acetate is then quickly re-assimilated and the biomass increases exponentially. To  avoid oxygen limitation, the feed rate is  finally kept constant to further increase the biomass concentration.

The oveflow metabolism model used is similar to the yeast_model, with a maximum glucose uptake rate above which additional glucose uptake is converted to acetate, which results in a maximum qO. This model gives a reasonable fit to experimental data with E. coli W3110 (Biotechnol. Prog. 1999, 15, 81−90). The inhibitory effect of acetate has not been included in this model.