The main essential constituents of agricultural wastes are lignocellulosic and fibrous components. These fibrous and lignocellulosic components are localized in cell wall of plants. The plant cell wall is viewed as an integrated
association of complex macromolecules forming a largely insoluble matrix. Lignocellulose refers to plant dry matter biomass, so called lignocellulosic biomass. It is the most abundantly available raw material for the production of
bio-fuel, mainly bio-ethanol. It is composed of carbohydrate polymers (cellulose, hemicellulose) and an aromatic polymer (lignin). These carbohydrate polymers
contain different sugar monomers (six and five carbon sugars) and they are tightly bound to lignin. Short and long term prospect of ethanol production from lignocellulosic biomass have been evaluated. Lignocellulosic biomass can be converted to ethanol by hydrolysis and subsequent fermentation. Pretreatment
process (Delignification) is needed to increase the yield of hydrolysis. The hydrolysis reaction is catalyzed by either acids or/and enzymes. A family of cellulases such as that provided by Tricoderma fungus is necessary for the
saccharification process and for complete enzymatic hydrolysis of cellulose. A anaerobic fermentation by yeast is to make hexose sugars to ethanol and carbon dioxide by the pyruvate decarboxylase-alcoholdehydrogenase (PDC-ADH)
system (decarboxylation of pyruvic acid to CO2 and acetaldehyde and the latter reduced to ethanol). Pentose-fermenting microorganisms are found among bacteria, fungi and yeasts. Microorganisms in general, metabolize xylose to
xylulose through two separate routes. Xylulose subsequently is phosphorylated to xylulose-5-phosphate that can be further catabolized via phosphate pentose pathway and the Embden-Meyerhof pathway to ethanol. L-Arabinose can
catabolized by engineered yeast to D-xylulose -5-P and finally to ethanol.