Treated ricebran hydrolysate was fermented anaerobically using Clostridium saccharoperbutylacetonicum N1-4 at an initial pH of 6 +/- 0.2 and an operating temperature of 30 degrees C for production of hydrogen. The effects of different pretreatment methods on the liberation of sugar from 100 g of ricebran per litre of medium (distilled water) were investigated. In addition, the effects of the pretreatment method on ricebran hydrolysates of different initial ricebran concentrations on liberated sugar as well as the effects of the initial inoculum concentration, ricebran (substrate) concentration, and FeSO4 center dot 7H(2)O concentration on the yield as well as the productivity of hydrogen were investigated. The combination of enzymatic hydrolysis and a boiling pretreatment method produced the most fermentable sugar, 29.03 +/- 0.0 g/L from 100 g of ricebran per litre of medium (distilled water), while the amount of sugar liberated by ricebran hydrolysates of different initial ricebran concentrations upon pretreatment monotonically increased with the initial ricebran concentration. The increment in substrate, inoculum, and FeSO4 center dot 7H(2)O concentrations had a significantly positive effect (p < 0.05) on both the yield and productivity of hydrogen. The maximum hydrogen gas yield (Y-P/S) and productivity of 3.37 mol-H-2 per mol-sugar consumed and 7.58 mmol/(L h), respectively, were obtained from ricebran hydrolysate with a 100 g/L ricebran concentration (equivalent to 28.59 +/- 1.27 g sugar/L). In other experiments, 0.03 g/L FeSO4 center dot 7H(2)O and 1.5 g/L inoculum resulted in the best hydrogen gas yield and productivity from ricebran hydrolysates. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.