H-2 can potentially be produced in a two-stage biological process: the fermentation of glucose by Escherichia coli HD701 and the photofermentation of the residual medium by Rhodobacter sphaeroides O.U. 001. In a typical batch fermentation, E. coli consumed glucose and produced H-2, organic end-products and biomass. Organic end-products and residual glucose were removed during subsequent photofermentation by R. sphaeroides, with associated growth and neutralization of pH. However, photoproduction of H-2 did not occur during photofermentation of the residual liquor per se due to the presence of fixed nitrogen compounds. Nevertheless, this two-stage approach could be applied to dispose of sugar-containing industrial wastes, H-2 being used for on-site power generation. (c) 2006 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.