Fig. 4

The succinate production of various engineered E. coli strains with fumarate as the substrate. a Succinate production of E. coli T110 expressing different combinations of genes derived from S. oneidensis MR-1 in the MES reaction. b The i–t curve (current versus time) of the MES system for fumarate reduction catalyzed by E. coli T110 and T110(pMtrABC, pFccA-CymA). The Negative electrode was poised at -0.65 V against the Ag/AgCl reference electrode. After 30 min, 10 mM fumarate was added into the MES medium. c Succinate production of E. coli 8739 expressing different combinations of genes derived from S. oneidensis MR-1 in the MES reaction. d The i–t curve (current versus time) of the MES system for the reduction of fumarate catalyzed by E. coli 8739 and 8739(pMtrABC, pFccA-CymA). e Succinate production by E. coli MG1655 expressing different combinations of genes derived from S. oneidensis MR-1 in the MES reaction. f The i–t curve (current versus time) of the MES system for fumarate reduction catalyzed by E. coli MG1655 and MG1655(pMtrABC, pFccA-CymA). The data represent the means of three experiments and the error bars represent their standard deviation. The significance of differences was calculated using Student’s t-test, asterisks indicate a significant difference compared with the control (***p < 0.001; **p < 0.01; *p < 0.05)