Molecular Mechanisms and Metabolic Engineering of Glutamate Overproduction in Corynebacterium glutamicum
Glutamate is a commercially important chemical. It is used as a flavor enhancer and is a major raw material for producing industrially useful chemicals. A coryneform bacterium, Corynebacterium glutamicum, was isolated in 1956 by Japanese researchers as a
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Molecular Mechanisms and Metabolic Engineering of Glutamate Overproduction in Corynebacterium glutamicum Takashi Hirasawa, Jongpill Kim, Tomokazu Shirai, Chikara Furusawa, and Hiroshi Shimizu
Abstract Glutamate is a commercially important chemical. It is used as a flavor enhancer and is a major raw material for producing industrially useful chemicals. A coryneform bacterium, Corynebacterium glutamicum, was isolated in 1956 by Japanese researchers as a glutamate-overproducing bacterium and since then, remarkable progress in glutamate production has been made using this microorganism. Currently, the global market for glutamate is over 2.5 million tons per year. Glutamate overproduction by C. glutamicum is induced by specific treatments—biotin limitation, addition of fatty acid ester surfactants such as Tween 40, and addition of b-lactam antibiotics such as penicillin. Molecular biology and metabolic engineering studies on glutamate overproduction have revealed that metabolic flow is significantly altered by these treatments. These studies have also provided insight into the molecular mechanisms underlying these changes. In this chapter, we review our current understanding of the molecular mechanisms of glutamate overproduction in C. glutamicum, and we discuss the advances made by metabolic engineering of this microorganism.
T. Hirasawa • H. Shimizu (*) Department of Bioinformatic Engineering, Graduate School of Information Science and Technology, Osaka University, 1-5 Yamadaoka, Suita, Osaka 565-0871, Japan e-mail: [email protected] J. Kim Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan T. Shirai RIKEN Biomass Engineering Program, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan C. Furusawa Quantitative Biology Center, RIKEN, 6-2-3 Furuedai, Suita, Osaka 565-0874, Japan X. Wang et al. (eds.), Reprogramming Microbial Metabolic Pathways, Subcellular Biochemistry 64, DOI 10.1007/978-94-007-5055-5_13, © Springer Science+Business Media Dordrecht 2012
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Keywords Anaplerotic pathways • Corynebacterium glutamicum • Glutamate • Metabolic engineering • NCgl1221 • OdhI • 2-Oxoglutarate dehydrogenase complex
Abbreviations 13
C-MFA CoA FBA FHA GC/MS GDH ICDH Km MFA MSG NMR ODHC PC PEPC TCA
13.1
13
C metabolic flux analysis coenzyme A flux balance analysis forkhead-associated gas chromatography/mass spectrometry glutamate dehydrogenase isocitrate dehydrogenase Michaelis-Menten constant metabolic flux analysis mono sodium glutamate nuclear magnetic resonance 2-oxoglutarate dehydrogenase complex pyruvate carboxylase phosphoenolpyruvate carboxylase tricarboxylic acid
Introduction
In 1908, Dr. Kikunae Ikeda identified monosodium glutamate (MSG) as the compound imparting the taste of Umami to numerous foods. Umami is distinct from other tastes such as bitter, sour, salty and sweet. Ikeda and his colleagues began to industrially produce MSG by subjecting wheat protein gluten to acid hydrolysis. Ajin
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