ABSTRACT
Bioethanol is the most attractive alternative to fossil fuel due to its high octane number, environmentally sustainable production and easy blending options with gasoline. Currently the major industrial production of bioethanol depends on fermentation of cane sugar or corn starch by yeast, that is the first generation bioethanol. To reduce the dependency on food crops the non-edible part of plants, the storage carbohydrate lignocellulose, is being extensively studied as an alternative resource for bioethanol production. Lignocellulose has a complex structure made up of two carbohydrate cellulose, hemicellulose and a polymer lignin. Hence rigorous chemical or physical pretreatment is required to increase the accessibility of carbohydrates to enzymes which is followed by enzymatic hydrolysis of cellulose into reducing sugars and fermentation of sugars to ethanol. The main hindrance for economical production of second generation cellulosic bioethanol is the cost of huge amount of cellulase enzymes required for hydrolysis. Consolidated bioprocessing where cellulase production, saccharification and fermentation all are performed in a single genetically engineered cell factory has been proposed to bring down the cost of production. This chapter discusses the recent advances in metabolic engineering for design and development of cell factories for integrated production of cellulosic ethanol.
