Chapter 4 : Ethanol, Biomass, and Clostridia

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A vigorous debate on gradual substitution of petroleum by use of renewable alternatives such as starch or sugar to ethanol or cellulosic biofuels dominates the political and economic agenda worldwide. Ethanol has been produced from sugarcane since the 1990s; an aggressive program has achieved the use of neat ethanol in new cars. There are various reports on lignocellulosic ethanol production using biomass. These indicate that ethanol from lignocellulosic biomass reduces “greenhouse gases” (GHG) emissions by about 80% compared to gasoline, whereas ethanol from corn reduces them by 20 to 30%. The cellulase system in comprises multiple enzyme complexes. In the case of hemicellulose, enzymatic saccharification by occurs, generating xylose and xylobiose; both are utilized by for production of ethanol, lactic acid, and acetic acid. The combination of both microorganisms in the production of ethanol has been central in the development of the consolidated bioprocessing concept of researchers. Although the coculture system is very promising, several barriers exist such as end product inhibition by the produced ethanol. This disadvantage can almost be counterbalanced by the process of ethanol distillation from dilute broths. The work by researchers on the structure of the cell surface multisubunit complex called the cellulosome has been very important for understanding the detailed interactions between the organism and its enzymes and the binding affinity to cellulose through the cellulosic binding domain.

Citation: Báez-Vásquez M, Demain A. 2008. Ethanol, Biomass, and Clostridia, p 49-54. In Wall J, Harwood C, Demain A (ed), Bioenergy. ASM Press, Washington, DC. doi: 10.1128/9781555815547.ch4
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Image of Figure 1.
Figure 1.

Production of ethanol from U.S. corn.

Citation: Báez-Vásquez M, Demain A. 2008. Ethanol, Biomass, and Clostridia, p 49-54. In Wall J, Harwood C, Demain A (ed), Bioenergy. ASM Press, Washington, DC. doi: 10.1128/9781555815547.ch4
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Image of Figure 2.
Figure 2.

A comparison of estimated selling prices of bioethanol from lignocellulosic biomass and bioethanol from corn.

Citation: Báez-Vásquez M, Demain A. 2008. Ethanol, Biomass, and Clostridia, p 49-54. In Wall J, Harwood C, Demain A (ed), Bioenergy. ASM Press, Washington, DC. doi: 10.1128/9781555815547.ch4
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Image of Figure 3.
Figure 3.

Ethanol production with a coculture system of and (modified from ).

Citation: Báez-Vásquez M, Demain A. 2008. Ethanol, Biomass, and Clostridia, p 49-54. In Wall J, Harwood C, Demain A (ed), Bioenergy. ASM Press, Washington, DC. doi: 10.1128/9781555815547.ch4
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