Enhancement of L-cysteine on continuous fermentative biohydrogen production

The research study plans to investigate the influence of L-cysteine on the continuous anaerobic fermentative biohydrogen production system, utilizing two continuously stirred tank reactors (CSTR) operated under two parallel controlling parameters; one added with L-cysteine continuously at 0.1 g/L with the inflow of water and the other without any addition. The oxidation-reduction potential (ORP), biomass, fermentation liquid end metabolites and characteristics of hydrogen production were inspected contrastively. In the reactor with L-cysteine addition, the time taken for ORP to decrease below-400 mV and ethanol-type fermentation formation took 1 day and 25 days respectively, however it took 10 days and 35 days in the other reactor in contrast. In the stable operating stage, the hydrogen production rate was 3.06 L/d in the reactor with L-cysteine addition, higher than 2.99 L/d in the other without addition. The results show that, L-cysteine accelerates the formation of low ORP environment, which is favored by ethanol-type fermentation, because it leads to a quick startup of continuous hydrogen production system, and enhances hydrogen production of the system.