Page 60 - Biofuels Refining and Performance

Energy and Its Biological Resources 43

Glucose Pyruvate Acetyl CoA Products
H
Formate 2
NADH Fd H 2
(NAD)

C H O + 2H O 2CH COO + 2CO + 4H 2
12
6
2
3
6
2
a b c d e
2 2 2
c d e
K =
ab 2
Figure 1.14 Hydrogen production.
Removal of or reducing concentrations of either CO or H or the com-
2
2
bination of both is likely to favor a forward reaction, i.e., to improve pro-
duction of H . Attempts to remove CO by collecting the evolved gases
2
2
through 25% (w) NaOH solution, using E. aerogenes (E 82005), showed
better production of H , which improved further by enriching nitroge-
2
nous nutrients in the culture media—from 0.52 moles of H per mole of
2
glucose, increased to 1.58 moles [9].
Similar attempts are made using E. cloacae and reducing the partial
pressure of H during the production of gases, by reducing the operat-
2
ing pressure of the reactor and simultaneous removal of CO [through
2
30% (w/v) KOH], maintaining an anoxic condition by flushing Ar at the
onset [10]; by reducing the operating pressure to 0.5 atm, the molar ratio
of H yield per mole of substrate doubled (1.9–3.9). Other technical and
2
economic benefits were also cited. There are other similar claims of
improved biohydrogen production [11], using altered nutrients (20 g of glu-
cose, 5 g of yeast extract, and 5 g/L of tryptone) and different mutants of
E. aerogenes HU-101. HU-101 and mutants A1, HZ3, and AAY, respec-
tively yielded 52.5, 78, 80, and 101.5 mmol of hydrogen per liter of media.

References
1. R. BuveI, M. J. Allen, and J. P. Massue. Living Systems as Energy Converters,
Amsterdam: North Holland, 1977.
2. H. Baltscheffsky. Origin and Evolution of Biological Energy, Amazon Company: United
Kingdom, 1996.
3. L. A. Kristofferson and V. Bokalders. Renewable Energy Technologies: Their
Applications in Developing Countries. A Study of the Beijer Institute and the Royal
Swedish Academy of Sciences, Oxford, Pergamon: Sweden, 1986.
4. M. Calvin. Photosynthesis as a resource for energy and materials, American Scientist
64, 270–278, 1976.
5. A. Nag and K. Vizaykumar. Environmental Education and Solid Waste Management,
New Age Publisher: New Delhi, India, 2006.
6. Proceedings of Bio-Energy Society (Department of Nonconventional Energy), CGO,
New Delhi, India, October 14–16, 1985.