Resumo

The full utilization of lignocellulosic biomass by fermentation of sugars such as glucose and xylose is essential for the economical accomplishment of the second generation bioethanol. These sugars are released by the action of cellulolytic and xylanolytic enzymes that hydrolyze cellulose and hemicellulose, respectively. The yeast Pseudozyma hubeiensis, isolated from the intestinal tract of a Chrysomelidae that is associated to sugarcane roots, has the ability to produce xylanase. Xylanases are glycosyl hydrolases that degrade xylan, the most abundant polysaccharide in hemicellulose, and have many commercial uses, such as the manufacture of paper, animal feed, bakery, juice and wine industries, xylitol production, and this project aims to study and characterize an endoxylanase produced by P. hubeiensis. The enzymatic activity of the supernatant of yeast induced by xylan appeared very high. Therefore, the xylanase produced by P. hubeiensis was purified by Affinity Chromatography, indicating that is has ~24 kDa, with high endoxylanase activity and according to the results of Mass Spectrometry, belongs to family 11 of glycosyl hydrolases. According to Circular Dichroism analysis, its secondary structure consists of β-sheets, a common characteristic of this family of enzymes. The physicochemical characterization of xylanase resulted in optimum pH equal to 4 and optimum temperature 55°C. Its enzymatic activity is affected by some ions, such as Zn2+, Mg2+ and Ca2+. The enzyme activity decreases with increasing branching of the substrate and the kinetics indicated a sigmoidal behavior characteristic of allosteric enzymes. According to Capillary Electrophoresis, the xylanase produces xylooligosaccharides of various sizes that can be used industrially as prebiotics. Thus, xylanase studied possesses considerable biotechnological importance, being promising in various industrial uses. Finacial support: FAPESP and CNPq, Brazil.