Identification of bottlenecks in penicillin production

Metabolic flux analysis (MFA) has recently gained importance as a tool for estimating fluxes in the central metabolism. MFA, which is based on metabolite balancing, may not, however, always yield enough information for a complete analysis of the central metabolism to be possible. Additional information can be obtained using specifically labelled substrates and subsequently measure the degree of label incorporation in the central metabolites. This approach has the following two advantages: A qualitative picture of the metabolism, in terms of active pathways, is obtained, and a quantitative analysis of the relative activities of the pathways may be performed. With these two objectives in mind, small-scale cultivations of Penicillium chrysogenum are carried out using specifically labelled glucose as the carbon source in a chemically defined medium. The biomass is harvested when the cultivation has reached an isotopic steady state. The subsequent analysis of the biomass, in terms of labelling patterns, is performed using GC-MS. This method has the advantage compared to the NMR-technique that only very small amounts of the metabolites are necessary.