Cellulases from fungi and bacteria and their biotechnological applications.

Cellulases (EC 3.2.1.4) catalyze the endohydrolysis of (1->4)-?-D-glucosidic linkages in cellulose, and play a significant role in nature by recycling this polysaccharide which is the main component of plant cell wall. Cellulases work in synergy with other hydrolytic enzymes in order to obtain the full degradation of the polysaccharide to soluble sugars, namely cellobiose and glucose, which are then assimilated by the cell. The enormous potential that cellulases have in biotechnology is the driving force for continuous basic and applied researches on these biocatalysts from Fungi and Bacteria. Nowadays, cellulases found application in many fields, such as animal feeding, brewery and wine, food, textile and laundry, pulp and paper industries. Moreover, the growing interest towards the conversion of lignocellulosic biomass to fermentable sugars has generated an increasing demand for cellulases and related enzymes. In fact, bioconversion of biomass has significant advantages over other alternative energy strategies because lignocellulose is the most abundant and renewable biomaterial on our planet. Bioconversion of lignocellulose is initiated primarily by microorganisms which are capable of degrading lignocellulosic materials. Several Fungi produce large amounts of extracellular cellulolytic enzymes, whereas bacterial and few anaerobic fungal strains mostly produce cellulolytic enzymes in a complex associated with the cell wall called cellulosome. However, the heterogeneous and recalcitrant nature of lignocellulosic waste represents an obstacle for an efficient saccharification process, and pre-treatment techniques are required to make the polysaccharide more accessible to the enzymatic action. Thermostable enzymes can offer potential benefits in the hydrolysis of pre-treated lignocellulosic substrates because the harsh conditions often required by several pre-treatments can be harmful for conventional biocatalysts. Their enhanced stability to high temperature and extreme operative parameters allow improved hydrolysis performance and increased flexibility with respect to process configurations, all leading to enhancement of the overall economy of the process. The present review gives an outline of several cellulases from Fungi e Bacteria (both mesophilic and [(extremo)thermophilic] that have been described in last years and application of these enzymes in some biotechnological fields with particular regard to lignocellulose bioconversion.