Hydrogen (H(2)) production and end-product synthesis were characterized in a novel, mesophilic, cellulolytic, anaerobic bacterium, Clostridium termitidis strain CT1112, isolated from the gut of the termite, Nasutitermes lujae. Growth curves, pH patterns, protein content, organic acid synthesis, and H(2) production were deter-mined. When grown on 2 gl(-1) cellobiose and 2 gl(-1) alpha-cellulose, C. termitidis displayed a cell generation time of 6.5 h and 18.9 h, respectively. The major end-products synthesized on cellobiose included acetate, hydrogen, CO(2), lactate, formate and ethanol, where as on cellulose, the major end-products included hydrogen, acetate, CO(2) and ethanol. The concentrations of acetate were greater than ethanol, formate and lactate on both cellobiose and a-cellulose throughout the entire growth phase. Maximum yields of acetate, ethanol, hydrogen and for-mate on cellobiose were 5.9, 3.7, 4.6 and 4.2 mmol l(-1) culture, respectively, where as on cellulose, the yields were 7.2, 3.1, 7.7 and 2.9 mmol l(-1) culture, respectively. Hydrogen and ethanol production rates were slightly higher in C. termitidis cultured on cellobiose when compared to alpha-cellulose. Although, the generation time on a-cellulose was longer than on cellobiose, H(2) production was favored corresponding to acetate synthesis, thereby restricting the carbon flowing to ethanol. During log phase, H(2), CO(2) and ethanol were produced at specific rates of 4.28, 5.32, and 2.99 mmol h(-1) g dry weight(-1) of cells on cellobiose and 2.79, 2.59, and 1.1 mmol h(-1) g dry weight(-1) of cells on alpha-cellulose, respectively. (C) 2008 Published by Elsevier Ltd on behalf of International Association for Hydrogen Energy.