Effect of redox potential regulation on metabolic flux distribution of succinate production by Actinobacillus succinogenes

The effect of redox potential regulation on metabolite flux distribution of Actinobacillus succinogenes NJ113 was studied by using the metabolic flux analysis method. The results showed that the flux of HMP and EMP were changed after ORP regulation. Under the optimal ORP(-350 mV) condition, the ratio of HMP to EMP was improved from 43.6:56.2 to 63.2:36.5 and thus the reducing power was better balanced. The value of NADH/NAD⁺ at the ORP of -350 mV was much higher than that without regulation. In the initial phase the NADH/NAD⁺ was increased from 2.19 to 8.73. Finally, the succinic acid flux increased from 114.5 mmol·(g DCW)^-1·h^-1 to 129.3 mmol·(g DCW)^-1·h^-1 with the metabolic flux of acetic acid and formic acid decreased by 30.6% and 30.2%, respectively. Succinic acid yield was increased from 75.46% to 89.34% with the productivity of 1.18 g·L^-1·h^-1.