Enhanced production of α-ketoglutarate by fed-batch culture in the metabolically engineered strains of Corynebacterium glutamicum

The fed-batch culture system was employed to enhance production of alpha-ketoglutarate (alpha-KG) by the strainsof Corynebacterium glutamicum, whose genes encoding the key enzymes responsible for the biosynthesis of L-glutamate from alpha-KG were deleted. In a shake flask fermentation, C. glutamicum JH110 in which the 3 genes, gdh (encoding glutamate dehydrogenase), gltB (encoding glutamate synthase), and aceA (encoding isocitrate lyase) were disrupted showed the highest production of alpha-KG (12.4 g/L) compared to the strains JH102 (gdh mutant), JH103 (gltB mutant), and JH107 (gdh gltB double mutant). In the fed-batch cultures using a 5 L-jar fermenter, the strain JH107 produced more alpha-KG (19.5 g/L), but less glutamic acid (23.3 g/L) than those produced by the parent strain HH109, as well as JH102. The production of alpha-KG was significantly enhanced and the accumulation of glutamicacid was minimized by the ammonium-limited fed-batch cultures employing C. glutamicum JH107. Further improvement of alpha-KG production by the strain JH107 was achieved through the ammonium-limited fed-batch culture with the feeding of molasses, and the levels of alpha-KG and glutamic acid produced were 51.1 and 0.01 g/L, respectively.