Thermophilic fermentative hydrogen production from xylose by Thermotoga neapolitana DSM 4359

Abstract

Biohydrogen production from xylose by Thermotoga neapolitana was investigated in batch culture using serum bottles and a continuously stirred anaerobic bioreactor (CSABR). The effect of various xylose concentrations on growth and H 2 production were studied in small batch culture for highly efficient H 2 production. The highest hydrogen production of 32.1 ± 1.6 mmol-H 2/L and maximum biomass concentration of 959.63 ± 47.9 mg/L were obtained at initial xylose concentration of 5.0 g/L. To develop a large-scale biohydrogen production system as well as overcome the problems in small batch culture, a continuously stirred anaerobic bioreactor was tested on T. neapolitana in both pH-uncontrolled batch culture and pH-controlled batch culture. The results showed that the production level of H 2 from fermentation in a pH-controlled batch culture was much higher than those from a pH-uncontrolled batch culture for H 2 production from xylose. The H 2 yield in a pH-controlled batch culture on xylose substrate was 2.22 ± 0.11 mol-H 2 mol −1 xylose consumed, which was nearly 1.2-fold higher than pH-uncontrolled batch cultures. In order to study the precise effect of a stable pH on hydrogen production, and metabolite pathway involved, cultures was conducted with pH-controlled at different levels ranging from 6.5 to 7.5. The maximum H 2 yield of 2.8 ± 0.14 mol-H 2 mol −1 xylose consumed was measured while the pH was maintained at 7.0. The acetic acid and lactic acid production were 2.98 ± 0.15 g/L and 0.36 ± 0.02 g/L, respectively.