ABSTRACT
Lignocellulosic biomass is a promising feedstock for fuel ethanol production because it is both readily available and less expensive than either corn or sugarcane. This chapter reviews advances in the development of microorganisms for ethanol production from lignocellulosic feedstocks and highlights those strategies that have demonstrated some measure of success. There are several advantages to the use of Saecharomyces cerevisiae in biomass fermentations. It ferments glucose to ethanol as virtually the sole product, and is known for its superior ethanol tolerance. A genetically engineered S. cerevisiae in which the xylose reductase, xylitol dehydrogenase, and xylulokinase genes were coordinately expressed can apparently ferment a mixture of 10% glucose and 5% xylose to ethanol within 2 days and with very little xylitol formation. The xylose-fermenting bacteria are recognized for their high fermentation rates, but only at the expense of low ethanol yields that result from the formation of numerous coproducts, e.g., acetate, succinate, lactate, and formate.
