Innovative Metabolic Pathway Design for Efficient L-Glutamate Production by Suppressing CO_2 Emission(MICROBIAL PHYSIOLOGY AND BIOTECHNOLOGY)

概要

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In the pathway of L-glutamic acid(L-Glu) biosynthesis in Corynebacterium glutamicum, 1 mol of L-Glu is synthesized from 1 mol of glucose at a cost of 1 mol of carbon dioxide(CO_2), with a maximum theoretical yield of 81.7% by weight. We have designed an innovative pathway for efficient L-Glu production employing phosphoketolase(PKT) to bypass the CO_2-releasing pyruvate dehy drogenase reaction, thereby increasing the maximum theoretical yield of L-Glu from glucose to up to 98.0% by weight(120% mol/mol L-Glu produced/glucose consumed). The xfp gene encoding PKT was cloned from Bifidobacterium animalis and overexpressed under the strong cspB promoter in C. glutamicum. A functional enzyme was detected in an L-Glu-producing strain of C. glutamicum(odhA). When cells of this producer strain with the xfp gene and those without the xfp gene were cultivated in a controlled fermentation system, the L-Glu production yield of the strain expressing the xfp gene was much higher than that of the original strain, coupled with the suppression of CO_2 emission. Consequently, we could successfully enhance L-glutamate production by installing the PKT pathway of B. animalis into C. glutamicum L-Glu metabolism, and this novel metabolic design will be able to increase L-Glu production yield beyond the maximum theoretical yield obtained from the conventional metabolic pathway of biosynthesis from glucose.
公益社団法人日本生物工学会の論文
2007-03-25