Equilibrium of the intracellular redox state for improving cell growth and l-lysine yield of Corynebacterium glutamicum by optimal cofactor swapping

BACKGROUND: NAD(H/(+)) and NADP(H/(+)) are the most important redox cofactors in bacteria. However, the intracellular redox balance is in advantage of the cell growth and production of NAD(P)H-dependent products. RESULTS: In this paper, we rationally engineered glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and isocitrate dehydrogenase (IDH) to switch the nucleotide-cofactor specificity resulting in an increase in final titer [from 85.6 to 121.4 g L(−1)] and carbon yield [from 0.33 to 0.46 g (g glucose)(−1)] of l-lysine in strain RGI in fed-batch fermentation. To do this, we firstly analyzed the production performance of original strain JL-6, indicating that the imbalance of intracellular redox was the limiting factor for l-lysine production. Subsequently, we modified the native GAPDH and indicated that recombinant strain RG with nonnative NADP-GAPDH dramatically changed the intracellular levels of NADH and NADPH. However, l-lysine production did not significantly increase because cell growth was harmed at low NADH level. Lastly, the nonnative NAD-IDH was introduced in strain RG to increase the NADH availability and to equilibrate the intracellular redox. The resulted strain RGI showed the stable ratio of NADPH/NADH at about 1.00, which in turn improved cell growth (μ(max.) = 0.31 h(−1)) and l-lysine productivity (q(Lys, max.) = 0.53 g g(−1) h(−1)) as compared with strain RG (μ(max.) = 0.14 h(−1) and q(Lys, max.) = 0.42 g g(−1) h(−1)). CONCLUSIONS: This is the first report of balancing the intracellular redox state by switching the nucleotide-cofactor specificity of GAPDH and IDH, thereby improving cell growth and l-lysine production. [Image: see text] ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12934-019-1114-0) contains supplementary material, which is available to authorized users.