A sequential approach to uncapping of theoretical hydrogen production in a sulfate-reducing bacteria-based bio-electrochemical system

Abstract

The presence of undesired methanogens with Sulfate-reducing bacteria (SRBs) is a serious challenge faced by the bioelectrochemical system (BES). In the present study, we investigate the impact of ammonia pre-treated electrodes on hydrogen production in a 600 ml anaerobic (BES) enriched with sulfate-reducing bacteria (SRBs) to inhibit the CH4 production for achieving the theoretical H2 production. The highest hydrogen production of 3.67 ± 0.31 M/M of glucose was recorded in the BES. The BES completely inhibited the growth of methanogens after the 7th cycle of operation. The higher hydrogen production efficiency of BES can be justified by assuming a higher hydrogen mass transfer from the electrode surface to the biofilm. In presence of sulfate, acetate acid type of the fermentation was dominating in hydrogen production, while limitation of SO42− switch over to the dominance of butyric acid type fermentative hydrogen production. Despite the sign of change in the acetate to butyric acid type metabolism, the BES system was able to uncap the theoretical hydrogen production. The notable change in vector orientation of H2, butyric acid, and hexanoic acid inferring the significant differences in the microbial community adapted on the electrodes in the R–NH3 and R-Cont. SEM image clearly showing ammonia-treated electrode harbour more microbial growth on the electrode surface. The ratio obtained for CH3 and CH2 for the R–NH3 and R-CONT of 1.316 and 1.755 respectively by FTIR stretching vibrations showing the difference in the bacterial species adapted on the bioanodes. Cumulative hydrogen production data was computed to confirm its validity of the Gompertz model, Richard model, and Logistic model. The Richard model was found in the best-fitted models for cumulative hydrogen production.