Effect of pH on hydrogen production from glucose by a mixed culture

The effect of pH on the conversion of glucose to hydrogen by a mixed culture of fermentative bacteria was evaluated. At 36 degreesC, six hours hydraulic retention, over 90% of glucose was degraded at pH ranging 4.0-7.0, producing biogas and an effluent comprising mostly fatty acids. At the optimal pH of 5.5, the biogas comprised 64 +/- 2% of hydrogen with a yield of 2.1 +/- 0.1 mol-H-2/mol-glucose and a specific production rate of 4.6 +/- 0.4 1-H-2/(g-VSS day). The effluent was composed of acetate (15.3-34.1%) and butyrate (31.2-45.6%), plus smaller quantities of other volatile fatty acids and alcohols. The diversity of microbial communities increased with pH, based on 16S rDNA analysis by denaturing gradient gel electrophoresis (DGGE). (C) 2002 Published by Elsevier Science Ltd.