Thermophilic hydrogen production from cellulose with rumen fluid enrichment cultures: Effects of different heat treatments

Elevated temperatures (52, 60 and 65 °C) were used to enrich hydrogen producers on cellulose from cow rumen fluid. Methanogens were inhibited with two different heat treatments. Hydrogen production was considerable at 60 °C with the highest H₂ yield of 0.44 mol-H₂ mol-hexose⁻¹ (1.93 mol-H₂ mol-hexose-degraded⁻¹) as obtained without heat treatment and with acetate and ethanol as the main fermentation products. H₂ production rates and yields were controlled by cellulose degradation that was at the highest 21%. The optimum temperature and pH for H₂ production of the rumen fluid enrichment culture were 62 °C and 7.3, respectively. The enrichments at 52 and 60 °C contained mainly bacteria from Clostridia family. At 52 °C, the bacterial diversity was larger and was not affected by heat treatments. Bacterial diversity at 60 °C remained similar between heat treatments, but decreased during enrichment. At 60 °C, the dominant microorganism was Clostridium stercorarium subsp. leptospartum.