The batch fermentations of two hyperthermophilic eubacteria Thermotoga maritima strain DSM 3109 and Thermotoga neapolitana strain DSM 4359 were carried out to optimize the hydrogen production. The simple and economical culture medium using cheap salts with strong buffering capacity was designed based on T. maritima basal medium (TMB). Both strains cultivated under strictly anaerobic conditions showed the best growth at temperature of 75-80 degrees C and pH of 6.5-7.0. The maximum cell growth of 3.14gDCW/L and hydrogen production of 342 mL H(2) gas/L were obtained, respectively, in the modified TB medium containing 7.5 g/L of glucose and 4 g/L of yeast extract. Hydrogen accumulation in the headspace was more than. 30% of the gaseous phase. Cells were also cultivated in cellulose-containing medium to test the feasibility of hydrogen production. (c) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.