The effect of L-malic acid and sodium glutamate, which serve as the carbon and nitrogen source, respectively, on hydrogen production by Rhodobacter sphaeroides O.U.001 has been investigated in a batch water jacketed glass column photobioreactor (PBR), which has an inner volume of 400 ml. The PER was operated at different carbon to nitrogen ratios at 32 degrees C with a tungsten lamp at a light intensity of 200 W m(-2). Carbon to nitrogen ratio was found to be an important parameter for bio-hydrogen production. Moreover, hydrogen gas production was dependent on certain threshold concentrations of sodium glutamate. L-malic acid consumption was found to be first order with respect to L-malic acid concentration, whereas sodium glutamate consumption was found to be second order with respect to glutamate concentration. It was concluded that there is a close relationship between the hydrogen production rate and substrate consumption rates. A kinetic model is developed, which relates hydrogen gas production per amount of biomass, L-malic acid, and sodium glutamate concentrations. (C) 1999 Elsevier Science B.V. All rights reserved.