Glycerol was used as a substrate for H-2 production by bacterium Enterobacter aerogenes in the test tubes and bioreactor. A BioFlo/CelliGen 115 bioreactor (10 L working volume) was utilized to conduct the experiments for conversion of glycerol into H-2 by E. aerogenes cells. The highest H-2 production rate was observed under 2% glycerol in the culture medium. The glycerol uptake efficiency by bacteria in the bioreactor was found to be 65% during the 6 day period, matching glycerol uptake efficiency observed in the test tubes experiment (65%).Hydrogen production from glycerol (2% glycerol, v/v) by E. aerogenes in the bioreactor and test tubes was measured over the 6 days, showing the maximal H-2 rate at 650 mL dry weight h(-1). The yield of H-2 production from glycerol at 0.89 mol/mol in the bioreactor was high, corresponding to the theoretical yield of 1 mol of H-2 per 1 mol of glycerol. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.