super(13)C NMR studies of the fluxes in the central metabolism of Corynebacterium glutamicum during growth and overproduction of amino acids in batch cultures

• Published in: Applied microbiology and biotechnology 1995-12, Vol.44 (3-4), p.489-495
• Main Authors: Sonntag, K, Schwinde, J, De Graaf, AA, Marx, A, Eikmanns, B J, Wiechert, W, Sahm, H
• Format: Article
• Language: English
• Subjects: Corynebacterium
• ISSN: 0175-7598

The carbon flux distribution in the central metabolism of Corynebacterium glutamicum was studied in batch cultures using [1- super(13)C]- and [6- super(13)C]glucose as substrate during exponential growth as well as during overproduction of L-lysine and L-glutamate. Using the super(13)C NMR data in conjunction with stoichiometric metabolite balances, molar fluxes were quantified and normalised to the glucose uptake rate, which was set to 100. The normalised molar flux via the hexose monophosphate pathway was 40 during exponential growth, whereas it was only 17 during L-glutamate production. During L-lysine production, the normalised hexose monophosphate pathway flux was elevated to 47. Thus, the carbon flux via this pathway correlated with the NADPH demand for bacterial growth and L-lysine overproduction. The normalised molar flux in the tricarboxylic acid cycle at the level of 2-oxoglutarate dehydrogenase was 100 during exponential growth and 103 during L-lysine secretion. During L-glutamate formation, the normalised flux through the tricarboxylic acid cycle was reduced to 60. In contrast to earlier NMR studies with C. glutamicum, no significant activity of the glyoxylate pathway could be detected. All experiments indicated a strong in vivo flux from oxaloacetate back to phosphoenolpyruvate and/or pyruvate, which might be due to phosphoenolpyruvate carboxykinase activity in C. glutamicum.