Lignocellulose refers to plant dry matter, so called lignocellulosic biomass. It is the most abundantly available raw material on the Earth for the production of bio-fuels, 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.

Lignocellulosic materials include a variety of materials such as sawdust, pop­lar trees, sugarcane bagasse, waste paper, brewer’s spent grains, switch grass, and straws, stems, stalks, leaves, husks, shells and peels from cereals like rice, wheat, corn, sorghum and barley, among others.

Lignocellulose wastes are accumulated every year in large quantities, causing environmental problems. The major constituents of lignocellulose are cellulose, hemicellulose, and lignin, polymers that are closely associated with each other con­stituting the cellular complex of the vegetal biomass. Basically, cellulose forms a skeleton, which is surrounded by hemicellulose and lignin. The chemical composi­tion of plants differs considerably and is influenced by genetic and environmental factors (Table 15.1).

On the other hand, amorphous regions within the cellulose crystalline structure have a heterogeneous composition characterized by a variety of different bonds. Ultimately, this asymmetrical arrangement, which characterizes amorphous regions, is crucial to the biodegradation of cellulose. The accessibility of cell wall polysac­charides from the plant to microbial enzymes is dictated by the degree to which they are associated with phenolic polymer.

Lignocellulose is a complex substrate and its biodegradation is not dependent on environmental conditions alone, but also the degradative capacity of the microbial population. The composition of the microbial community charged with lignocellu- lose biodegradation determines the rate and extent thereof.