Abstract
Only a third of the biomass of sugarcane is processed into ethanol, while the other two thirds are dropped as bagasse and straw. Cellulose and hemicellulose are the most abundant polymers in sugar cane bagasse, and have a very complex arrangement in the cell wall. Cellulases and hemicellulases are glycoside hydrolases responsible for the complete hydrolysis of plants cell-wall polysaccharides. Filamentous fungi are the largest source for cell-wall degrading enzymes prospection, especially those of the genus Aspergillus. Aspergillus and Trichoderma are extraordinary in their ability to secrete large amounts of proteins into the culture medium. Most fungal proteins undergoes glycosylation co- or posttranslational in the endoplasmic reticulum (ER) and/or Golgi complex, and therefore in essence are glycoproteins. However, this proposal will focus on two major objectives: 1) Effect of N-glycans on functional properties of glycoside hydrolases: investigate possible functional changes of a GH11 endo-xylanase variants, non-glycosylated, hypo- and hyper-glycosylated, cloned from Penicillium funiculosum. These changes include increased or reduced activity, abnormal pattern of hydrolysis products, changes in kinetic constants (Km and Kcat), changes in secondary structure and variations in specificity and affinity to different substrates; 2) Constitutive expression of hacA and cpcA (genes involved in ER stress and unfolded protein response) in A. nidulans: we propose the construction of strains expressing constitutively hacAi and gcn4p/cpcA, systematically checking the heterologous production of a target protein, GH12 xyloglucanase (XegA) from Aspergillus clavatus (Acla_029940). (AU)
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