Abstract:Lysine, as a primary metabolite, is normally produced by Corynebacterium glutamicum, and its synthesis is closely related to intracellular NADPH levels. However, the regulatory mechanisms between L-lysine biosynthesis and the cofactor NADPH in C. glutamicum are still poorly understood. In this paper, the lysine-producing strain C. glutamicum XQ-5 was used as the starting strain, and the recombinant strain C. glutamicum XQ-5Δzwf::pgi with low NADPH levels was constructed by blocking the pentose phosphate pathway, reducing the intracellular NADPH level in each 104 cells from 3.57×10-8 μmol to 1.12×10-8 μmol. In addition, the recombinant strain C. glutamicum XQ-5Δpgi::(zwf-gnd) with high NADPH level was constructed by enhancing the pentose phosphate pathway. It increased the intracellular NADPH level in each 104 cells from 3.57×10-8 μmol to 1.8×10-7 μmol. Cell growth, bacterial mass and intracellular by-product accumulation of strains under different NADPH levels were significantly different through shake-flask fermentation. Based on the results of transcriptomics and other experiments, the expression level of the panD gene in the recombinant strain C. glutamicum XQ-5Δpgi::(zwf-gnd) was significantly increased. The lysine production of recombinant strain C. glutamicum XQ-5ΔpanDΔpgi::(zwf-gnd) with inactivated panD gene increased to 55 g/L, an increase of 14.3% to the original strain C. glutamicum XQ-5, which suggested that the increased expression level of panD gene was one of the reasons for the decline in lysine levels based on the over-expression of pentose phosphate pathway. This study provides a solid theoretical basis for further studies on the regulation mechanism of cofactor NADPH on L-lysine biosynthesis.
