CAZymes secreted by basidiomycetes and their application in the hydrolysis of lignocellulosic materials

Wood decay basidiomycetes are recognized as the most capable organisms in degradation of lignified biomass. These fungi could be a potential source of new enzymes for biomass hydrolysis. Commercial cellulases supplemented with enzymes from Laetiporus sulfureus and Pleorotus ostreatus were used for the enzymatic hydrolysis of pretreated sugarcane bagasse. The hydrolysis performed at suboptimal enzyme load of commercial cellulases (5 FPU/g of substrate) supplemented with the basidiomycetes enzymes showed initial conversion rates of glucan and xylan similar to those obtained with a full load of commercial cellulases (10 FPU/g substrate). This result was achieved even with the half of the original cellobiohydrolase (CBH) activity in the reaction media. The identification of the basidiomycetes proteins was performed by LC MS/MS and bioinformatic analysis in genome databases. In the P. ostreatus extract, 43 proteins classified as cellulases (5), hemicellulases (12), esterases (8), oxidoreductases (6), and pectinases (11) were considered relevant for the degradation of lignocellulosic substrates. In the case of L.sulphureus extract, 18 proteins were potentially involved in biomass conversion: cellulases (4), hemicellulases (9) esterases (3) and oxidoreductases (2). The three main enzyme groups involved in cellulose hydrolysis (GH7-CBH; GH5-EG; GH3-BGL) were identified in both wood decay fungal extracts. A small GH45-EG that retains homology with other GH45-EGs and also some fungal CBM1-swollenins was found only in the L.sulphureus extract. Both GH3-beta-glucosidases found in wood decay extracts were similar to an interesting GH3-Cel3A from Hypocrea jecorina that is more active in cellotriose and cellotetraose olygosaccharides than in cellobiose.

Acknowledgements: CAPES, FAPESP 14/06923-6