Biofuels in Perspective

Biological Hydrogen Production by Anaerobic Microorganisms 215
the H2-producing reactions. Dependent on the electron carrier used, energy-conserving
membrane-bound hydrogenases as well as cytoplasmic hydrogenases appear to catalyze
the ultimate H2 forming reactions. However, to make biohydrogen formation feasible we
need to increase the H2/glucose ratio beyond the current maximum of 4. To achieve this,
future research will focus on metabolic engineering to decrease the amount of acetate or
on acetate oxidation by electricity-mediated electrolysis or photofermentation.
Acknowledgment
Our research on biological hydrogen formation was financially supported by the Dutch
Programme Economy, Ecology, Technology (EET), a joint initiative of the Ministries of
Economic Affairs, Education, Culture and Sciences, and of Housing, Spatial Planning
and the Environment (EETK03028 BWPII) and the Commission of the European Communities,
Sixth Framework Programme, Priority 6, Sustainable Energy Systems (019825
HYVOLUTION).
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