Characterization of hydrogen production and microbial community shifts in microbial electrolysis cells with L-cysteine

L-cysteine is used to improve efficiency in anaerobic biological systems as an oxygen scavenger, electron shuttle and substrate source. The performance of MEC by addition of L-cysteine was investigated during start-up and operation phases, respectively. Results showed that the maximum current density of 6.36 ± 0.14 A/m², hydrogen yield of 1.08 ± 0.05 m³/m³ and energy efficiency of 130% were achieved with L-cysteine adding during operation phase. By contrast, the addition of L-cysteine during the start-up phase reduced the energy efficiency by more than 30%. The microbial community analysis revealed that a higher microbial community richness and diversity were achieved, the enrichment of Sulfuricurvum, Sulfurospirillum, Desulfovibrio and other electroactive microorganisms indicated their relative abundance could be regulated by L-cysteine during start-up phase when L-cysteine was added. This study provided an alternative method to enhanced hydrogen production and a better understanding of the mechanism of L-cysteine action in MEC performance.