**5. Fungal enzyme sets for lignocellulosic degradation**

Fungi play a central role in the degradation of plant biomass, producing an extensive ar‐ ray of carbohydrate-active enzymes responsible for polysaccharide degradation. The en‐ zyme sets for plant cell wall degradation differ between many fungal species, and our understanding about fungal diversity with respect to degradation of plant matter is es‐ sential for the improvement of new strains and the development of enzymatic cocktails for industrial applications.

Carbohydrate-active enzymes are usually classified in different families, based on amino acid sequence of the related catalytic module. An extensive and detailed database present‐ ing these hydrolytic enzymes can be found at www.cazy.org (CAZymes, **C**arbohydrate**A**ctive En**Zy**mes) [32]. The fungal carbohydrate-active enzymes commonly (but not always) present a carbohydrate-binding module (CBM), which promotes the association of the en‐ zyme with the substrate. A review on fungal enzymes related to plant biomass degradation describes that such enzymes are assigned to at least 35 glycoside hydrolase (GH) families, three carbohydrate esterase (CE) families, and six polysaccharide lyase (PL) families [33]. Al‐ though the classification of CWDEs into families facilitates our view about a specific en‐ zyme, the activities of these enzymes are quite complicated to classify, because some families can contain several enzymatic activities. This is especially important because CA‐ Zymes usually act in a synergistic way, complementing the substrate specificity of each oth‐ er, in order to degrade complex polysaccharide matrices. For instance, GH5 comprises many catalytic activities, such as endoglucanases, exoglucanases and endomannanases [34]. This section will describe the fungal enzymatic set required for the main polysaccharides present in the plant biomass: cellulose, hemicellulose and pectin. A brief description of enzymes re‐ quired for lignin degradation will be depicted. Because most of the research in cellulase/ hemicellulase field is performed using the fungi *T. reesei* and *A. niger*, the focus of our dis‐ cussion about CWDEs will be conducted based on these microorganisms, although some as‐ pects related to other fungal species could be mentioned to demonstrate the diversity of carbohydrate-active enzymes.
