ABSTRACT
Ethanol production by anaerobic mesophilic or thermophilic fermentation is one way to use renewable resources. This chapter outlines the production of ethanol by Clostridium species from xylose and cellulose, components of biomass such as agricultural and wood residues, and describes genetic improvements of these microorganisms, as efficient ethanol producers, that used mutagenesis techniques and gene manipulation. To improve the ethanol productivity from xylose as well as glucose in the Clostridia, decreasing the production of by-products such as acetic acid and lactic acid, and enhancing their ethanol tolerance have been performed by use of mutagenesis or enrichment culture techniques. Some species of Clostridium could be useful for ethanol production from xylose and cellulose contained in agricultural and forest wastes because of the direct conversion of such substrates to ethanol. After all, some mutants of Clostridium that ferment xylose or cellulose have been obtained, but no wild or genetically improved strains of Clostridium are currently suitable for industrial purposes.
