Wednesday, August 1, 2007 - 9:30 AM
S150
Glutamate Dehydrogenase in Penicillium chrysogenum is Involved in Regulation of beta-lactam Production
Jette Thykaer1, Kanchana Rueksomtawin1, Henk Noorman2, and Jens Nielsen1. (1) Biocentrum - Technical University of Denmark, Center for Microbial Biotechnology, Soeltofts plads, Building 223, DK-2800 Kgs Lyngby, Denmark, (2) Industrial Pharmaceutical Products Division, DSM- Anti-Infectives, Wateringsweg 1, PO Box 1, NL-2600 MA Delft
Metabolic engineering has proven to be a rational alternative for improving beta-lactam producing strains. Several research groups have been working specifically on optimisation of the beta-lactam production of Penicillium chrysogenum e.g. through gene dosage studies. It is however, of equal importance to gain insight into other aspects of the metabolism to establish a general overview in order to apply metabolic engineering for further improvement of the production strains. In this work, the interactions between the redox metabolism, the central metabolism and the secondary metabolism were investigated. Especially the role of NADPH-dependent glutamate, in this perspective, was examined. This was pursued by disruption of the gdhA-gene, encoding the NADPH-dependent glutamate dehydrogenase, in two different industrial strains of P. chrysogenum. Detailed physiological characterisation showed that disruption of gdhA resulted in significant decreases in the maximum specific growth rates of around 30% for both the strains. Furthermore, disruption of gdhA had a severe effect on the production as the production of beta-lactam was completely eliminated in the constructed strains. However, the specific growth rate of the references strains could be restored in the transformant strains by addition of glutamate, but despite the glutamate addition, the mutant strains remained non-productive. From the results of this work it is argued that besides being the key enzyme in ammonium assimilation, the NADPH-dependent glutamate dehydrogenase appears to be involved in regulation of beta-lactam production in industrial strains of P. chrysogenum.