Ultrasonication was evaluated as a pretreatment for biological hydrogen production from glucose in batch studies, in comparison with heat-shock pretreatment, acid pretreatment, and base pretreatment. The optimized sonicatdon energy for hydrogen production using anaerobic digester sludge was 79kJ/gTS. Sonication with temperature control (less than 30 degrees C) increased volumetric hydrogen production by 120% over the untreated sludge, and by 40% over the heat-shock and acid pretreated sludge, with a marginal (similar to 10%) increase in hydrogen production rate. Upon comparing the molar hydrogen yield in sonicated sludge with and without temperature control, the deleterious effect of heat on some hydrogen producers as reflected by a 30% decrease in yield to 1.03 mol H(2)/mol glucose is evident. Sonication with temperature control affected a 45% increase in molar hydrogen yield to 1.55 mol H(2)/mol glucose over heat-shock pretreatment at 70 degrees C for 30 min and acidification to pH 3.0 for 24 h at 4 degrees C. Sonication with temperature control produced a biomass yield of 0.13 g VSS/g COD, as compared to 0.24 g VSS/g COD for the untreated sludge. The hydrogen yield increased linearly with the molar acetate to butyrate ratio and decreased linearly with the biomass yield. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.