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Category: Applied and Industrial Microbiology
Energetic Aspects of Methanogenic Feeding Webs, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555815547/9781555819057_Chap14-1.gif /docserver/preview/fulltext/10.1128/9781555815547/9781555819057_Chap14-2.gifAbstract:
The degradation of organic matter by methanogenesis is the most complex and the most efficient way of transforming organic matter into an energetically useful product. This chapter deals with the complex cooperations in methanogenic microbial communities under different treatment regimes and the technological perspectives in the optimization of energy recovery from biomass treatment in the present and in the future. Energy-rich products other than methane can be produced fermentatively from biomass. A real breakthrough in the treatment of high-strength wastewaters was the development of the Upflow Anaerobic Sludge Blanket (UASB) technology developed by G. Lettinga and his coworkers in Wageningen, The Netherlands, in the 1980s. Although the reason for the development of the microbial aggregates remains obscure, the UASB technology has proven to be applicable to many different types of high-load wastewaters and has conquered the market in this field nearly worldwide. All major constituents of living biomass or organic waste materials can be converted to methane plus CO2, with the only exceptions being lignin and lignocellulose. It is the energetic efficiency that makes the overall process possible at all, but it also limits its kinetic and dynamic versatility.
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Network of the methanogenic feeding chain. Depolymerizations and primary fermentations are carried out by the same fermenting organisms. Note the decrease of chemical complexity with every step.
Basic concept of the energy metabolism of a syntrophically fermenting bacterium (“secondary fermenter” in Fig. 1 ). ATP is formed in the oxidative branch of the metabolism by substrate-level phosphorylation, and part of it is consumed in the release of electrons, e.g., as molecular hydrogen, in a reversed electron transport step.
Changes of Gibbs free energy for secondary fermentations and methane-forming reactions