Hydrogen gas production potentials of acid-hydrolyzed and boiled ground wheat were compared in batch dark fermentations under mesophilic (37 degrees C) and thermophilic (55 degrees C) conditions. Heat-treated anaerobic sludge was used as the inoculum and the hydrolyzed ground wheat was supplemented by other nutrients. The highest cumulative hydrogen gas production (752 ml) was obtained from the acid-hydrolyzed ground wheat starch at 55 C and the lowest (112 ml) was with the boiled wheat starch within 10 days. The highest rate of hydrogen gas formation (7.42 ml H(2) h(-1)) was obtained with the acid-hydrolyzed and the lowest (1.12 ml H(2) h(-1)) with the boiled wheat at 55 degrees C. The highest hydrogen gas yield (333 ml H(2) g(-1) total sugar or 2.40 mol H(2) mol glucose) and final total volatile fatty acid (TVFA) concentration (10.08 g L(-1)) were also obtained with the acid-hydrolyzed wheat under thermophilic conditions (55 degrees C). Dark fermentation of acid-hydrolyzed ground wheat under thermophilic conditions (55 degrees C) was proven to be more beneficial as compared to mesophilic or thermophilic fermentation of boiled (partially hydrolyzed) wheat starch. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.