Methane free biohydrogen production from carbon monoxide using a continuously operated moving bed biofilm reactor

Biological water-gas shift (WGS) reaction is a green and sustainable alternative to thermochemical-catalytic WGS process for hydrogen production from carbon monoxide (CO). However, CO tolerant carboxydotrophic microbes for hydrogen production and scaling up the technology using a bioreactor system present challenges in successful application of this technology. This study demonstrated the capability of anaerobic microbial consortium for biohydrogen production from CO using a moving bed biofilm reactor (MBBR). The CO conversion pathway followed by the anaerobic biomass was first elucidated by inhibiting the methanogens present using 2-bromoethanesulfonate (BES) at an optimum concentration of 10 mmol/L. An increase in inlet CO concentration to the MBBR enhanced the H₂ production, but the CO conversion efficiency was low. More than 80% CO conversion efficiency was obtained only for a low inlet CO concentration. A maximum H₂ concentration of 19.5 mmol/L along with 2 mmol/L of acetate were obtained for 36 mmol/L of inlet CO concentration in the bioreactor. The carbon flux analysis showed that the CO was mainly utilized for methane free H₂ production, and only <10% of carbon flux was diverted towards acetate formation. Overall, this study demonstrated that MBBR system can be used for steady state biohydrogen production over a prolonged operation period.