Engineering Corynebacterium glutamicum for fast production of l-lysine and l-pipecolic acid

The Gram-positive Corynebacterium glutamicum is widely used for fermentative production of amino acids. The world production of l-lysine has surpassed 2 million tons per year. Glucose uptake and phosphorylation by C. glutamicum mainly occur by the phosphotransferase system (PTS) and to lesser extent by inositol permeases and glucokinases. Heterologous expression of the genes for the high-affinity glucose permease from Streptomyces coelicolor and Bacillus subtilis glucokinase fully compensated for the absence of the PTS in Δhpr strains. Growth of PTS-positive strains with glucose was accelerated when the endogenous inositol permease IolT2 and glucokinase from B. subtilis were overproduced with balanced translation initiation rates using plasmid pEKEx3-IolTBest. When the genome-reduced C. glutamicum strain GRLys1 carrying additional in-frame deletions of sugR and ldhA to derepress glycolytic and PTS genes and to circumvent formation of l-lactate as by-product was transformed with this plasmid or with pVWEx1-IolTBest, 18 to 20 % higher volumetric productivities and 70 to 72 % higher specific productivities as compared to the parental strain resulted. The non-proteinogenic amino acid l-pipecolic acid (l-PA), a precursor of immunosuppressants, peptide antibiotics, or piperidine alkaloids, can be derived from l-lysine. To enable production of l-PA by the constructed l-lysine-producing strain, the l-lysine 6-dehydrogenase gene lysDH from Silicibacter pomeroyi and the endogenous pyrroline 5-carboxylate reductase gene proC were overexpressed as synthetic operon. This enabled C. glutamicum to produce l-PA with a yield of 0.09 ± 0.01 g g−1 and a volumetric productivity of 0.04 ± 0.01 g L−1 h−1.To the best of our knowledge, this is the first fermentative process for the production of l-PA from glucose.