Based on hydrogen production by photosynthetic bacteria (PSB) in biofilm bioreactor, in the present study, a substrate solution with specific inlet concentration flowing past a circular cylinder with biochemical reaction in an attached thin PSB biofilm is numerically simulated by applying the lattice Boltzmann method (LBM). A non-equilibrium extrapolation method is employed to handle the velocity and concentration curved boundary. The model is validated by available theoretical and numerical results in terms of the drag and lift coefficients and concentration profiles. The good agreement demonstrated that LBM is an effective method to simulate nonlinear biochemical reaction systems with curved boundary. The velocity profile and concentration distributions of the substrate and hydrogen are determined, and the effect of Reynolds number on mass transfer characteristics is also discussed by introducing Sherwood number. The simulation results show that for both the substrate and product the concentration extension along X- and Y-directions decrease with increasing Reynolds number. The highest hydrogen concentration is obtained at the back of the cylinder. Furthermore, increasing Reynolds number results in decreasing substrate consumption efficiency, while hydrogen yield almost keeps a steady value. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.