The observation strategy developed in this paper consists of an H-infinity Luenberger observer coupled to a classical super-twisting observer. The H-infinity Luenberger observer uses the biohydrogen flow rate measured at the reactor output to estimate the glucose and the biomass concentrations inside the reactor. These estimations are taken by the super-twisting observer to estimate the glucose concentration at the reactor input. First, pseudo-stoichiometric and kinetic parameters of the bioreactor model are identified. Two semi-definite optimization problems are then proposed to compute the observer gains. Results show that the biomass is a sensitive state variable. In spite of this, the glucose estimated at the reactor input correctly follows the experimental data and the estimation error remains close to zero in the complete period of time considered. (C) 2015 Elsevier Ltd. All rights reserved.