Placed within the field of renewable energy, the enzymatic pre-treatment of biomass (the enzymatic degradation of plant wall polysaccharide) is becoming a more attractive alternative than the use of chemicals pre-treatment or mechanical processes. Furthermore, the biodegradation of cellulose by cellulases and cellulosomes produced by numerous microorganisms, represents the largest carbon flow from carbon fixed for atmospheric CO2. Likewise, this process is very important for various processes for agro-industrial waste that can be used for bioenergy to replace fossil fuels. Enzymatic hydrolysis of cellulose involves the synergistic action of at least three enzymes, endoglucanase, exoglucanase or cellobiohydrolase, and ²-glucosidase. One of the groups most abundant polysaccharide in nature, hemicellulose are classified according to the sugar present in its molecule, and the basic structure is composed by: xylan, galacto-glucomannan, ±-1,5-L-arabinan and arabinogalactan. Xylan is a polymer of xylose, but in nature, is usually associated with other sugars forming glucuronoxylan, glucuroarabinoxylan, glucomannan, arabinogalactans, and galactoglucomannan. In this context, hemicellulases are a diverse group of enzymes that hydrolyze hemicelluloses. These enzymes have many biotechnological applications and their link structure/ function, is a subject of intense research. The attraction of filamentous fungi as expression machinery is based on your natural ability to secrete large amounts of protein (mainly hydrolytic enzymes) to the medium. Compared with other systems available for expression of heterologous proteins in liquid cultures, filamentous fungi show great performance, high yield and an inexpensive option with respect to nutritional requirements. The main focus of this proposal is to study and consolidate Aspergillus nidulans (strain A773) as a model for rapid and stable heterologous expression and secretion of cellulases and hemicellulases. Our main objective is to develop a collection of recombinant strains which overexpress the different enzyme activities involved in the degradation of plant cell wall polysaccharides. In addition to study the functional properties of these enzymes, with broad biotechnological applications that include the production of bioethanol, in this study we intend to develop strains that over-express two or more synergistic cellulolytic and hemicellulolycic activities.
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