Bioconversion of carbon dioxide to succinate by Citrobacter

Carbon dioxide as a feedstock for synthesizing chemicals and fuels attracts numerous efforts via biological or chemical approaches. A newly Citrobacter BD11 was detected with distribution of 71.31 % in reservoir samples by metagenomic sequencing, and can convert CO2 to succinic acid with hydrogen production under anaerobic condition. The pathway of hydrogen production and the succinic acid synthesis was explored by whole-genome sequencing and real-time quantitative polymerase chain reaction. The results showed the positive influences of pH, hydrogen pressure and magnesium ions on succinic acid production. The stage transition of hydrogen production and utilization was detected, and the nonlinear relationship between succinic acid production and exogenous carbon dioxide was proved. Under optimized conditions, the carbon fixation rate of 1.77 g/L*d and the succinate production rate of 7.51 g/L*d were finally achieved at pH = 7.0 with 50 KPa of hydrogen pressure and 4.0 g/L of MgCl2. This study demonstrated that this Citrobacter could be a promising platform for hydrogen production and convert CO2 to diverse acids.