Gene Amplification of aceA and aceB in Lysine-producing Corynebacterium glutamicum ssp. lactofermentum ATCC21799

The role of glyoxylate bypass in lysine production by Corynebacterium glutamicum ssp. lactofermentum ATCC21799 was analyzed by using cloned aceA and aceB genes which encode enzymes catalyzing the bypass. Introduction of a plasmid carrying aceA and aceB to the strain increased enzyme activities of the bypass to approximately 5 fold on acetate minimal medium. The strain with amplified glyoxylate bypass excreted 25% more lysine to the growth medium than the parental strain, apparently due to the increased availability of intracellular oxaloacetate. The final cell yield was lower in the strain with amplified glyoxylate bypass. These changes were specific to the lysine-producing C. glutamicum ssp. lactofermentum ATCC21799, since the lysine-nonproducing wild type Corynebacterium glutamicum strain grew faster and achieved higher cell yield when the glyoxylate bypass was amplified. These findings suggest that the lysine producing C. glutamicum ssp. lactofermentum ATCC21799 has the ability to efficiently channel oxaloacetate, the TCA cycle intermediate, to the lysine biosynthesis pathway whereas lysine-nonproducing strains do not. Our results show that amplification of the glyoxylate bypass efficiently increases the intracellular oxaloacetate in lysine producing Corynebacterium species and thus results in increased lysine production.