Effects of culture redox potential on succinic acid production by Corynebacterium crenatum under anaerobic conditions

During mixed-acid fermentation by Corynebacterium crenatum under anaerobic conditions, two moles of NADH are required to synthesize 1 mol of succinic acid. In this work, four controlled culture redox potentials and different carbon sources with different oxidation states were used to investigate the possibility of enhancing the succinic acid production by increasing the availability of NADH. When the culture redox potential was −300 mV, the yield of succinic acid was 0.31 g/g, representing a 72% increase compared with the yield when the culture redox potential was −40 mV. Meanwhile, the molar ratio of succinic acid/lactic acid increased from 0.27 to 0.48. When 0.1% neutral red was added to the acid production medium, the yield of succinic acid was 0.25 g/g, and the molar ratio of succinic acid/lactic acid was 0.38. Both values were higher than those obtained from glucose only (0.19 g/g, 0.26) or gluconate (0.05 g/g, 0.18). A higher NADH/NAD+ ratio and increased enzymatic activity could be achieved to enhance the succinic acid production by manipulating the culture to a more reductive environment.

► Corynebacterium crenatum was first used to produce succinic and lactic acid.
► Reducing the redox potential level was used to increase the availability of NADH.
► Yield of succinic acid increased significantly by reducing the redox potential level.
► The effect of different carbon source on succinic acid production was investigated.
► Addition of neutral red enhanced the succinic acid production.