Enzymology of hemicellulose degradation

Strains of the genus Trichoderma are not classified solely as a group containing the best cellulase producers. They are also very efficient producers of other types of polysaccharide hydrolases, which include a whole array of hemicellulolytic enzymes. These enzymes hydrolyze the non-cellulosic plant polysaccharides which have been named "hemicelluloses" and which are found in plant cell walls in close association with cellulose (Eriksson et al., 1990). Hemicelluloses are heteropolysaccharides composed of two or more monosaccharides such as D-xylose, L-arabinose, D-mannose, D-glucose, D-galactose and 4-0-methyl-D-glucuronic acid. Some of them are partially esterified with acetic, ferulic and p-coumaric acids. The primary structure of hemicelluloses depends on the source and can vary even between different tissues of a single plant. Often two or three different hemicelluloses occur in the same plant species, but in different proportions.