A one-dimensional two-phase flow and transport model is presented for a packed bed photobioreactor with transparent gel granules containing immobilized photosynthetic bacterial cells. The inherently coupled two-phase flow and mass transport, along with the biochemical reactions occurring in the photobioreactor are taken into account. The source term in the species conservation equation of the substrate is derived from a local transport model for a single gel granule. Model predictions of the glucose consumption efficiency and hydrogen production rate are in good agreement with experimental data. The results show that the photoinhibition of immobilized cells appears at incident light intensities higher than 6000 lux. It is the most suitable for photo-hydrogen production under neutral conditions and 30 degrees C of the influent substrate solution. Moreover, a high influent substrate solution flow rate results in a large hydrogen production rate due to the improved substrate transport from the bulk solution to gel granules. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.