The off-gas from acetone-butanol-ethanol (ABE) fermentation was firstly used to be CO2 source (co-substrate) for succinic acid production. The optimum ratio of H-2/CO2 indicated higher CO2 partial pressures with presence of H-2 could enhance C-4 pathway flux and reductive product productivity. Moreover, when an inner recycling bioreactor was used for CO2 recycling at a high total pressure (0.2 Mpa), a maximum succinic acid concentration of 65.7 g.L-1 was obtained, and a productivity of 0.76 g.L-1.h(-1) and a high yield of 0.86 g.g(-1) glucose were achieved. Furthermore, the hydrogen content was simultaneously enriched to 92.7%. These results showed one successful attempt to reuse the off-gas of ABE fermentation which can be an attractive CO2 source for succinic acid production. (C) 2016 Elsevier Ltd. All rights reserved.