The employment of hemicellulose fractions from bagasse acid (HF-AC-rich in xylose) and hydrothermal (HF-HT-containing high amounts of xylooligosaccharides) pretreatments led to yields of 265 and 177 mL(H2/gcarbohydrate) after 18 and 45 h of fermentation, respectively. The anaerobic sludge used as inoculum was able to hydrolyze the xylooligosaccharides of HF-HT into simpler sugars, enabling microbial hydrogen production. The acid hydrolysis of xylooligosaccharides in HF-HT before fermentation improved the productivity by 30% and showed similar yield (231 mL(H2/gcarbohydrate)). The adaptive phase for HF-HT consumption was influenced by the hydrolytic step and by inhibitors, as the kinetics of hydrolyzed HF-HT was deeply affected in the first 18 h compared to HF-AC. Higher amounts of HF-AC in the media promoted fermentation inhibition, which could be related to the increased concentrations of acetic acid and carbohydrates, two factors that enhance the system osmolarity. (C) 2019 Elsevier Ltd. All rights reserved.