High-rate hydrogen production from galactose in an upflow anaerobic sludge blanket reactor (UASBr)

High-rate hydrogen production from galactose and rapid granule formation were achieved in a mesophilic (37 degrees C) upflow anaerobic sludge blank reactor (UASBr). Hybrid immobilized cells were seeded to a CSTR fed with galactose (15 g L-1) at a hydraulic retention time (HRT) of 12 h for 12 days, after which the mixed liquor from the CSTR was transferred to the UASBr. Rapid granule formation was observed after 5 days of initial UASBr operation at 6 h HRT and further enhanced at 3 h HRT. The peak hydrogen production rate (HPR) and hydrogen yield (HY) of 32.7 L L-1 d(-1) and 1.95 mol mol(-1) galactose were attained at the HRT of 3 h with an organic loading rate (OLR) of 120 g L-1 d(-1). Microbial community analysis characterized by pyrosequencing of 16S rRNA genes showed that the proportion of Clostridium increased during the HRT at 3 h, whereas Bacilli proportions dominated at 6 h HRT.