Simulating Process Limitations In Microbial Cultivation

By Michael H. Limberg, Stephan Zelle, Christiane Schlottbom, and Marco Oldiges

In large-scale industrial bioprocesses, the presence of gradients in critical process parameters, such as dissolved oxygen (DO), pH, and substrate concentration, can be observed. They result in inhomogeneous growth conditions within the bioreactor/fermentor and can affect cell yield and/or productivity. Scale-down approaches at the laboratory scale are a tool to analyze the effects of the inhomogeneity.

Scientists at the Forschungszentrum Jülich have been using a cultivation set-up consisting of two connected stirred-tank reactors (STRs) to simulate inhomogeneous cultivation conditions as they can occur in production scale. In this application note, we describe the effects of oscillating DO and substrate concentation.

This study exemplifies the benefits of flexible benchscale bioreactor solutions and advanced bioprocess control software. Individual control of parallel operated bioreactors allowed different vessel sizes, individual parameter set-points, and multiple cultivation phases to be implemented easily.