This paper investigated the enhancement effect of nanometre-sized metallic (Pd, Ag and Cu) or metallic oxide (FexOy) nanoparticles on fermentative hydrogen production from glucose by a Clostridium butyricum strain. These nanoparticles (NP) of about 2-3 nm were encapsulated in porous silica (SiO2) and were added at very low concentration (10(-6) mol L-1) in batch hydrogen production test. The cultures containing iron oxide NP produced 38% more hydrogen with a higher maximum H-2 production rate (HPR) of 58% than those without NP or with silica particles only. The iron oxide NP were used in a 2.5 L sequencing-batch reactor and showed no significant effect on the yields (established at 2.2 mol(hydrogen) mol(glucose)(-1)) but an improvement of the HPR (+113%, reaching a maximum HPR of 86 mL(hydrogen) L-1 h(-1)). These results suggest an improvement of the electron transfers trough some combinations between enzymatic activity and inorganic materials. (C) 2012 Elsevier Ltd. All rights reserved.