Abstract: NADPH plays important roles in regulating cell growth and L-lysine synthesis in Corynebacterium glutamicum. A recombinant strain with blocked NADPH biosynthesis was constructed by deleting the genes of glucose-6-phosphate dehydrogenase (zwf)and malic enzyme (malE) and by replacing NADP+-dependent isocitrate dehydrogenase gene (icdCg) with Streptococcus mutans NAD+-dependent isocitrate dehydrogenase gene (icdSm). Compared with C. glutamicum LYS, the levels of intracellular NADH and NADH/NAD+in the recombinant strain increased by 38.58% and 53.84%, respectively, while the intracellular NADPH significantly decreased by 89.51%, and intracellular NADPH/NADP+ decreased by 93.13%. Meanwhile, the recombinant strain showed slower cell growth and its glucose metabolism significantly lowered during shake-flask fermentation. As a result, the biomass reduced 4.36% and the yield of L-lysine decreased by 87.69%, together with more by-products (pyruvate and lactate etc.) accumulated in cells. This study provides a basis for further studies on physiological mechanisms of NADPH that regulates intracellular microenvironment of L-lysine producing strains.
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2019, Vol. 45 
