Hydrogen production by Escherichia coli is mediated by the formate hydrogenlyase (FHL) complex. E. coli strain HD701 cannot synthesize the FHL complex repressor, Hyc A. Consequently, it has an up-regulated FHL system and can, therefore, evolve hydrogen at a greater rate than its parental wild type, E. coli MC4100. Resting cells of E. coli strain HD701 and MC4100 were set up in batch mode in phosphate buffered saline (PBS) to decouple growth from hydrogen production at the expense of sugar solutions of varying composition. Strain HD701 evolved several times more hydrogen than MC4100 at glucose concentrations ranging from 3 to 200 mM. The difference in the amount of H-2 evolved by both strains decreased as the concentration of glucose increased. The highest rate of H-2 evolution by strain HD701 was 31 ml h(-1) ODunit-1 l(-1) at a glucose concentration of 100 mM. With strain MC4100, the highest rate was 16 ml h(-1)OD(unit)(-1) l(-1) under these conditions. Experiments using industrial wastes with a high sugar content yielded similar results. In each case, strain HD701 evolved hydrogen at a faster rate than the wild type, showing a possible potential for commercial hydrogen production. (C) 2003 Elsevier Science Inc. All rights reserved.