Encyclopedia of Geobiology

2011 Edition
| Editors: Joachim Reitner, Volker Thiel


Reference work entry
DOI: https://doi.org/10.1007/978-1-4020-9212-1_90

Fermentation is a route of obtaining energy from the oxidation of organic substrates using an endogenous electron acceptor (usually an organic compound). The energy yield in fermenting systems is limited when compared to respiration. Nevertheless, fermentation still allows growth under conditions when external, inorganic electron acceptors are lacking, or when iron as part of the electron carriers in the respiratory chain is not available and therefore an electron transport chain cannot be synthesized. Common fermentation substrates are sugars, which are present in large amounts in the environment, for example, as photosynthesis products and constituents of plant cell wall material. Microbial sugar fermentation pathways encompass lactic acid fermentation, alcoholic fermentation, and propionate fermentation, according to the major metabolic products generated. Another important fermentation pathway is acetoclastic methanogenesis, that is, fermentation of acetate to CO2 and CH4, which...

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© Springer Science+Business Media B.V. 2011