Power to hydrogen-oxidizing bacteria: Effect of current density on bacterial activity and community spectra

Abstract

Hydrogen-oxidizing bacteria (HOB) can utilize hydrogen, oxygen, and carbon dioxide as electron donor, electron acceptor, and carbon source, respectively. These bacteria can convert hydrogen and carbon dioxide to biomass which is different from hydrophilic denitrification. “Power to HOB”, a new supplementary to “Power to Gas”, was proposed and demonstrated in this study, in which HOB were cultivated via in-situ consuming hydrogen generated by water electrolysis. The objects of this work were to explore the effect of current density on HOB activity and microbial community. The results showed good activity of enriched HOB that the nitrate consumption rate was 21 mg/L/d in batch and continuous modes under the current density (CD) of 2.14 mA/cm2. The cyclic voltammetry curve demonstrated the electric activity of HOB that redox peaks were 0.330 V and 0.195 V at corresponding CDs of 2.14 mA/cm2 and 4.29 mA/cm2, respectively. Finally, the community spectra revealed that the percentage of Cupriavidus sp. TA19 decreased by 15.59% (2.14 mA/cm2 vs 4.29 mA/cm2), and Pseudonocardia sp. YK32 increased by 38.31%. Moreover, Cupriavidus sp. TA19 was reported as HOB for polyhydroxyalkanoate (PHA, degradable plastics) production. Pseudonocardia sp. YK32 was also reported as HOB and the function was unknown. Thus, “Power to HOB” can be a new supplementary to “Power to Gas” and the results extend HOB applications.