Effect of fermentation temperature on hydrogen production from xylose and the succession of hydrogen‐producing microflora

Abstract

Abstract 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 from xylose using a mixed culture over a wide temperature range (35–65°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°C (1.11 and 1.30 mol‐ H 2 mol −1 ‐xylose consumed, respectively). Butyrate and acetate were the major liquid metabolites at 35–60°C. While at 65°C the main by‐product was ethanol. Polymerase chain reaction‐denaturing gradient gel electrophoresis ( PCR‐DGGE ) analysis indicated that Clostridium species were dominant at 35–40°C, while Thermoanaerobacterium dominated at 45–60°C. Both species were found at 65°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 structures were formed at mesophilic, transition, thermophilic and extreme‐thermophilic conditions, resulting in different metabolic pathways of xylose and hydrogen production capacity. © 2017 Society of Chemical Industry