Monday, May 5, 2008
6-23

Production and preliminary chemical and biochemical characterization of Aspergillus awamori β-glucosidase and xylanase

Ricardo S. T. Sposina1, Rodrigo R. B. Olivieri1, Félix G. Siqueira2, Edivaldo X. F. Filho2, and Elba Bon1. (1) Biochemistry - Chemistry Institute, Federal University of Rio de Janeiro, Instituto de Quimica, sala 539 - Cidade Universitaria, Ilha do Fundao, Rio de Janeiro, Brazil, (2) Cell Biology, University of Brasília, Cidade Universitaria, Brasília, Brazil

The filamentous fungi Aspergillus awamori produces cellulolytic and hemicellulolytic enzymes that can be used for biomass degradation into sugars that can be used for bioethanol production. This microorganism also produces high levels of β-glucosidase (EC 3.2.1.21) that is critical for the biomass ethanol technology, as this enzyme hydrolyses cellobiose into its two glucose monomers.  As such it minimizes end-product inhibition of cellulolytic enzymes and provides glucose for the ethanol fermentation.  The same microorganism also produces the enzyme xylanase (EC 3.2.1.8), that hydrolyzes the xylosidic linkages in xylan that is the major component of hemicellulose. The present study aims the chemical and biochemical characterization of Aspergillus awamori β-glucosidase and xylanase. Enzymes were produced under optimized conditions using wheat bran as carbon source. The culture supernatant was fractionated by ultrafiltration, gel filtration and ion-exchange chromatography. SDS-PAGE was used to evaluate the extent and nature of the purification. Protein separation through gel filtration resulted in the identification of two peaks with β-glucosidase activity and one with xylanase activity. Further fractionation of a selected β-glucosidase peak using CM-Sepharose, resulted in two peaks showing enzyme activity. The peak with xylanase activity was further separated into three peaks with xylanase activity using a Q-Sepharose column. The study for the characterization of the enzymes produced by Aspergillus awamori aims the formulation of an enzymes cocktail to be used for the hydrolysis of sugar cane bagasse.

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