A functional hydrogen producing consortium was isolated from soil by heat pre-treatment technique and hydrogen production at different substrate concentration was evaluated. The forest soil was heat pre-treated at 65, 80, 95, 105 and 120 degrees C temperature for 1 h. As revealed by PCR-DGGE analysis and hydrogen yield, the hydrogen producing microbial community changed with increase in heat pretreatment temperatures giving potential hydrogen producing consortium at 95-105 degrees C soil pre-treatment. The maximum hydrogen production rate, hydrogen yield and cumulative hydrogen with 15-20 g glucose were 1390-1576 mL/L/day, 1.83-1.93 mol H(2)/mol glucose, and 2966-3146 mL H(2)/L, respectively. The metabolic pathways shifted from ethanol-type to acetate formate type as soil pre-treatment temperature increased from 65 to 120 degrees C. The soil heat pre-treatment approach is effective for isolating hydrogen producing natural Clostridium consortium from the soil as enumerations of the functional strains need specific temperature range to florish. (C) 2010 Elsevier Ltd. All rights reserved.