Fermentative hydrogen production with xylose by Clostridium and Klebsiella species in anaerobic batch reactors

Hydrogen production was obtained from low concentrations of xylose metabolized by heat treated inoculum obtained from the slaughterhouse wastewater treatment UASB reactor installed in Brazil. The molecular biological analysis Clostridium and Klebsiella species, recognized as H2 and volatile acid producers, in addition to Burkholderia species and uncultivated bacteria. The assays were carried out in batch reactors: (1) 630.0 mg xylose/L, (2) 1341.0 mg xylose/L, (3) 1848.0 mg xylose/L and (4) 3588.0 mg xylose/L. The following yields were obtained: 3% (0.2 mol H2/mol xylose), 8% (0.5 mol H2/mol xylose), 10% (0.6 mol H2/mol xylose) and 14% (0.8 mol H2/mol xylose), respectively. The end products obtained were acetic acid, butyric acid, methanol and ethanol in all of the anaerobic reactors. The concentrations of xylose did not inhibit microbial growth and hydrogen production. This suggested that low concentrations of xylose should be added to wastewater to produce hydrogen.