Lysine and glutamate production by Corynebacterium glutamicum on glucose, fructose and sucrose: roles of malic enzyme and fructose-1,6-bisphosphatase.

In the biotechnological production of L-lysine and L-glutamate by Corynebacterium glutamicum media based on glucose, fructose or sucrose are typically used. Glutamate production by C. glutamicum was very similar on glucose, fructose, glucose plus fructose and sucrose. In contrast, lysine production of genetically defined C. glutamicum strains was significantly higher on glucose than on the other carbon sources. To test whether malic enzyme or fructose-1,6-bisphosphatase might limit growth and lysine on fructose, glucose plus fructose or sucrose, strains overexpressing either malE which encodes the NADPH-dependent malic enzyme or the fructose-1,6-bisphosphatase gene fbp were generated. Overexpression of malE did not improve lysine production on any of the tested carbon sources. Upon overexpression of fbp lysine yields on glucose and/or fructose were unchanged, but the lysine yield on sucrose increased twofold. Thus, fructose-1,6-bisphosphatase was identified as a limiting factor for lysine production by C. glutamicum with sucrose as the carbon source.