How to Determine Interdependencies of Glucose and Lactose Uptake Rates for Heterologous Protein Production with E. coli.

Induction by lactose is known to have a beneficial effect on the expression of soluble recombinant proteins in E. coli harboring the T7 expression system (e.g., E. coli BL21(DE3)). As lactose is a metabolizable inducer, it needs to be supplied continuously to prevent depletion and thus only partial induction. Overfeeding and accumulation of lactose or glucose on the other hand can lead to osmotic stress. Thus, it is of utmost importance to know the possible feeding ranges. Here, we show a fast method using a simple mechanistic model to characterize E. coli strains harboring the T7 expression system regarding their ability to take up lactose and glucose. This approach reduces experimental work and the gained data allows running a stable and robust bioprocess without accumulation of lactose or glucose.