l-Glutamic acid (l-Glu) is an industrially important amino acid for the production of the flavor enhancer, monosodium-l-glutamate (MSG), which expresses a savory taste known as umami. The fundamental fermentation process for MSG production was established in 1956 and is based on the l-glutamateproducing bacterium Corynebacterium glutamicum, which was originally isolated from a soil sample. Since the discovery of this epoch-making production method, extensive metabolic engineering studies designed to improve l-glutamate production have been conducted using the genomic information of C. glutamicum. This chapter focuses on recent studies of the molecular mechanism of l-glutamate secretion and metabolic pathway design for efficient overproduction of l-glutamate from glucose in C. glutamicum strains. The mechanism of l-glutamate overproduction is unique, and it has been demonstrated that the product of the NCgl1221 gene, which is homologous to mechano-sensitive channels, plays a crucial role in l-glutamate secretion. It has also been shown that the specific activity of the 2-oxoglutarate dehydrogenase complex decreases during l-glutamate overproduction and that the enzymatic activity is controlled by a novel regulatory mechanism that involves OdhI and serine/threonine protein kinases. On the other hand, a new metabolic pathway was designed to enhance l-glutamate production by bypassing the CO 2 -releasing pyruvate dehydrogenase reaction in the glycolytic pathway by introducing heterologous phosphoketolase. This attempt improved the conversion yield of l-Glu and reduced the CO 2 emission level during the fermentation process of l-glutamate overproduction by C. glutamicum.