Depending on the choice of the promoter system for protein expression, glucose concentration has to be optimised.
In our case, the glucose concentration in the 300-l scale was controlled automatically. This was done in the 2-l fed-batch fermentation without dialysis with protein expression and in the fermentation without protein expression and an initial ratio of dialysate to fermentation volume of Vdialysate/Vfermenter=1. The automatic control based on online-glucose measurements and a minimal variance control algorithm derived from fedbatch fermentations of Candida boidinii (Wedy, 1992). Glucose concentration was controlled to 2 g l−1 in the early growth phase to allow maximum growth rates. With the beginning of dialysis at a cell density of 10 g l−1, the set point was changed to 0.7 g l−1 and kept constant also during protein expression phase.