BACKGROUND: Hydrogen production through anaerobic dark fermentation is considered to be a potential biological process for xylose utilization. Temperature is one of the most important environmental factors, however, most studies have been carried out over a small temperature range. Batch tests were carried out to investigate the temperature effect on hydrogen production fromxylose using a mixed culture over awide temperature range (35-65 degrees C). Hydrogen production, metabolite distribution and dynamics of microbial communities were investigated. RESULTS: Hydrogen-producing cultures were successfully enriched at each tested temperature. Two peaks of fermentation temperature for hydrogen production were observed at 35 and 55 degrees C (1.11 and 1.30 mol-H2 mol-1-xylose(consumed), respectively). Butyrate and acetatewere the major liquidmetabolites at 35-60 degrees C. While at 65 degrees C the main by-productwas ethanol. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis indicated that Clostridium species were dominant at 35-40 degrees C, while Thermoanaerobacterium dominated at 45-60 degrees C. Both species were found at 65 degrees C, but with lowest microbial community diversity. CONCLUSION: Hydrogen production efficiency was mainly affected by the liquid metabolite distributions, which depended mainly upon the temperature. Several microbial community structureswere formed at mesophilic, transition, thermophilic and extreme-thermophilic conditions, resulting in differentmetabolic pathways of xylose and hydrogen production capacity. (C) 2017 Society of Chemical Industry