Thermophilic dark fermentation of acid hydrolyzed waste ground wheat for hydrogen gas production

Batch dark fermentation experiments were performed to investigate the effects of biomass and substrate concentration on bio-hydrogen production from acid hydrolyzed ground wheat at 55 °C. In the first set of experiments, the substrate concentration was constant at 20 g total sugar L⁻¹ and biomass concentration was varied between 0.52 and 2.58 g L⁻¹. Total sugar concentration was varied between 4.2 and 23.7 g L⁻¹ in the second set of experiments with a 1.5 g L⁻¹ constant biomass concentration. The highest cumulative hydrogen formation (582 mL, 30 °C, 1 atm), formation rate (5.43 mL h⁻¹) and final total volatile fatty acid (TVFA) concentration (6.54 g L⁻¹) were obtained with 1.32 g L⁻¹ biomass concentration. In variable substrate concentration experiments, the highest cumulative hydrogen (365 mL) and TVFA concentration (4.8 g L⁻¹) were obtained with 19.25 g L⁻¹ initial total sugar concentration while hydrogen gas formation rate (12.95 mL h⁻¹) and the yield (200 mL H₂ g⁻¹ total sugar) were the highest with 4.2 g L⁻¹ total sugar concentration.