Extreme-thermophilic biohydrogen production from lignocellulosic bioethanol distillery wastewater with community analysis of hydrogen-producing microflora

Extreme-thermophilic biohydrogen production from distillery wastewater was investigated in batch and continuous-mode operation. Hydrogen-producing mixed culture was enriched by repeated batch cultivations. Effect of temperature and pH on biohydrogen yield was investigated in batch experiments. The highest hydrogen yield of 196. mL/g-volatile solidsaddded (VSadded) was obtained at 70 °C and pH 7.0 in batch culture. Continuous biohydrogen production was performed in CSTR reactor with yield of 172.0 mL/g-VSadded at HRT (hydraulic retention time) of 4 days. The main metabolic products were acetate, lactate, and ethanol. Community structure of hydrogen-producing microflora was investigated by 16S rRNA gene sequence analysis. The microorganisms involved in both batch and continuous-mode operation were similar and hydrogen production was carried out by a group of extreme-thermophilic bacterial species related to Thermotoga, Coprothermobacter, Caldanaerobacter, Thermobrachium, and Caldicellulosiruptor.

► Biohydrogen production from distillery wastewater was investigated and hydrogen yield of 172.0 mL/g-VSadded was obtained in CSTR at 70 °C. ► Hydrogen-producing mixed culture was enriched by repeated batch cultivations. ► Bacterial species related to Thermotoga and Coprothermobacter species were found to be the dominant bacteria in the mixed cunture.