Metabolic engineering for L-lysine production by Corynebacterium glutamicum

Corynebacterium glutamicum has been used since several decades for the large-scale production of amino acids, esp. L-glutamate and L-lysine. After initial successes of random mutagenesis and screening approaches, further strain improvements now require a much more rational design, i.e. metabolic engineering. Not only recombinant DNA technology but also mathematical modelling of metabolism as well as metabolic flux analysis represent important metabolic engineering tools. This review covers as state-of-the-art examples of these techniques the genetic engineering of the L-lysine biosynthetic pathway resulting in a vectorless strain with significantly increased dihydrodipicolinate synthase activity, and the detailed metabolic flux analysis by 13C isotopomer labelling strategies of the anaplerotic enzyme activities in C. glutamicum resulting in the identification of gluconeogenic phosphoenolpyruvate carboxykinase as a limiting enzyme.