抄録
Corynebacterium glutamicum has been used for the industrial production of amino acids. Since it grows most efficiently at 30 degrees, much energy is required for elimination of heat for its industrial fermentation. C. efficiens can grow at higher temperature than C. glutamicum and therefore, is expected to reduce cost for the heat elimination, despite its poor ability of amino acids overproduction. The aim of this study is to elucidate the difference in metabolic fluxes of above two strains, which provides a basis for breeding new strains with better productivity. For this purpose, we analyzed the metabolic fluxes using 13C labeling patterns of amino acids which are obtained by GC-MS and NMR measurements. For flux analysis, first we defined a set of equations representing the changes of 13C labeling pattern of amino acids by metabolic reactions. Since it is difficult to solve the equations analytically, Levenberg-Marquardt method was used to estimate the metabolic fluxes from the 13C labeling patterns of amino acids which were derived from intermediate metabolites. To check the validity of this approach, we started the calculation from labeling patterns of amino acids obtained by a set of given metabolic fluxes, and confirmed that the estimated fluxes converged into the expected values independently of the initial conditions, even if the back fluxes in metabolic reactions are introduced. Using this method, the result of the flux analysis in two strains was presented. The results show that in both strains the flux through anaplerotic pathway, on which phosphoenolpyruvate (PEP) / pyruvate (Pyr) synthesized through the glycolysis and the pentose phosphate pathway was converted to oxaloacetate, was approximately 40 %, and the back fluxes were same. The existence of anaperotic pathways from PEP / Pyr to oxaloacetate and from oxaloacetate to PEP / Pyr was confirmed in C. efficiens as well.
