Résumé : [en] Hydrogen has received wide attention in the last decades as a clean energy vector. The majoradvantage of energy generation from hydrogen is the near-zero carbon emissions, since theutilization of hydrogen, either via combustion or via fuel cells, results in pure water. Recently,there has been increasing interest on the biological production of hydrogen gas from renewablebiomass such as carbohydrates from agriculture or agro-food industries. This specific anaerobicdigestion is called dark fermentation and is involved in the classic anaerobic digestion producingmethane. Indeed, in a two-step process, i.e. when acido- and aceto-genesis are carried out in adifferent bioreactor than methanogenesis, it is feasible to generate separated biogas flowscontaining either H2 or CH4 depending on specific operating parameters.This paper deals with the comparison of the first stage performances whether operated inoptimum conditions for H2 production with a mixed culture or a pure Clostridium butyricumstrain. Hydrogen yields of about 1.75 and 2.3 mol H2/mol glucose were achieved respectively.The metabolites, mainly acetate and butyrate, contained in the spent medium were efficientlyconverted to methane in a second anaerobic digester with a methane yield of about 170 ml/gCOD initially fed in the first stage.