Modelling the effects of glucose feeding on a recombinant E. coli fermentation

A simple unstructured model is described and compared with experimental data for fed-batch fermentations. The process studied is typical of the most common industrial recombinant fermentation in which temperature induced E. coli produces high yields of a heterologous protein (4 g met-asp-Bovine Somatotropin/l) using a complex peptone feed and a glucose feed. The model accurately predicts the effect of glucose feeding and shows that there is an optimal glucose feedrate to maximize productivity. At higher glucose feedrates, acetate levels become inhibitory and at lower levels glucose starvation occurs. The model is novel since it combines terms for acetate production and inhibition, effect of peptone feeding and temperature induction into a single relatively simple unstructured model. However the present model is unable to predict the effect of induction at different cell densities and reasons for this are suggested.