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Qiu C.,Tianjin Chengjian University | Qiu C.,Tianjin Key Laboratory of Aqueous Science and Technology | Zheng Y.,Tianjin Chengjian University | Zheng J.,Tianjin Chengjian University | And 5 more authors.
Energy and Fuels | Year: 2016

Anaerobic dark fermentation biohydrogen production from xylose was investigated under mesophilic (35 °C) and thermophilic (55 °C) conditions at various initial pH (5.0-10.0) and substrate concentrations (2.5-12.5 g/L). In addition, the microbial community structure variations under different temperatures were analyzed. It was demonstrated that the maximum hydrogen yield (1.24 mol-H2/mol-xylose) was obtained with substrate concentration of 7.5 g/L and initial cultivation, pH 7.0, at 35 °C, with butyrate, acetate, and ethanol as the major byproducts. The increase of substrate concentration resulted in accumulation of volatile fatty acids (VFAs), especially propionate, and a decrease in final pH under mesophilic conditions. However, the hydrogen yield increased along with the increase of substrate concentration at 55 °C with butyrate and ethanol as the main metabolite. Stable pH of the system could be maintained even at high xylose concentration up to 12.5 g/L due to a low level of VFAs accumulation. A lower hydrogen yield of 1.14 mol-H2/mol-xylose was obtained at thermophilic condition, while a stable operation condition could be achieved and maintained more easily. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis showed that microbial community structures of both systems were dominated with bacterial species related to Clostridium, while the thermophilic system had fewer hydrogen-producing microbial species than that at mesothermal condition. © 2016 American Chemical Society.

PubMed | Tianjin Chengjian University and Tianjin Key Laboratory of Aqueous Science and Technology
Type: Journal Article | Journal: World journal of microbiology & biotechnology | Year: 2016

Biohydrogen is considered as one of the most promising energy alternatives considering the climate and energy crisis. The dark fermentative hydrogen production from xylose at extreme thermophilic condition (70C) using mixed culture was conducted in this study. The effects of initial pH values (ranged from 5.0 to 10.0) and substrate concentrations (ranged from 2.5 to 15.0g/L) on the hydrogen production, substrate degradation and metabolite distributions were investigated using batch-mode operations. Results showed that initial substrate pH values in the neutral region (6.0-7.0) were beneficial for hydrogen production. The fermentation at initial pH 7.0 and 7.5g/L xylose reached an optimal hydrogen yield of 1.29mol-H

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