Biology of L-lysine overproduction byCorynebacterium glutamicum

The Gram positive bacteriumCorynebacterium glutamicum is used for the production of L-lysine. This review focuses on the progress achieved in the past five years for a deeper understanding of lysine overproduction. This period also coincides with decisive progress in the use of genetic engineering techniques for analysing and increasing the metabolite flux inC. glutamicum. It was thus demonstrated that thein vivo activity of the allosterically controlled aspartate kinase is important for flux control, but in addition also the amount of the dihydrodipicolinate synthase. An outstanding feature ofC. glutamicum is the split lysine biosynthesis pathway. NMR investigations have clearly shown that both pathways are simultaneously usedin vivo and that the flux ratio depends on nitrogen availability. The cellular synthesized lysine is eventually exported into the external medium through a specific carrier. Interestingly lysine producers have other export characteristics so that the carrier properties also seem to be important for increased metabolite flux.