Cellulosic hydrogen production and microbial community characterization in hyper-thermophilic continuous bioreactor

A continuous stirred tank reactor was used for the dark hydrogen fermentation of cellulose by mixed microflora at hyper-thermophilic temperature (70 ± 1 °C) for 240 days. A total of twenty six batch experiments were conducted to investigate the effect of temperature on the activity of cellulosic-hydrogen producing bacteria. The results show that the system reached a steady state condition after 90 days. A stable hydrogen yield of 7.07 ± 0.23 mmol H₂/g cellulose was maintained for 150 days with acetate, butyrate, ethanol and propionate as main soluble byproducts. Analysis of 16S rRNA sequences showed that the cellulolytic bacteria were close to Thermoanaerobacterium genus. The cellulosic-hydrogen producing bacteria were able to utilize the cellulose or glucose within a wide range of fermentation temperatures (45–80 °C) to produce hydrogen. The activation energy for cellulose and glucose were estimated at 133.2 and 117.7 kJ/mol, respectively.