English

Oliveira Da Silva Patricia,Henrique Betini Jorge,De Carvalho Peixoto-Nogueira Simone,De Lourdes Teixeira De Moraes Polizeli Maria Maria,Fonseca Zanoelo Fabiana,Cristina Giannesi Giovana,Cavalieri De Alencar Guimarães Nelciele,Rossato Marchetti Clarice,Rita Marques Maria

doi:10.5897/ajb2015.14943

Abstract

The production of xylanase without cellulase is required for prebleaching of pulp in pulp and paper industry. Aspergillus flavus produced high levels of xylanase on agricultural residues with wheat bran and sugarcane bagasse (4.17 U/mg), and wheat bran and corncob (2.97 U/mg). Xylanase was found to be stable at 45°C with 100% of its original activity remaining after 2 h incubation. At 50°C, xylanase was stable for the first twenty minutes, and had half-life of 50 min. The pH stability for the xylanase from A. flavus was most stable in the range of pH 3.0-8.0 retaining more that 100% activity after 1 h. The addition of 5% glycerol, mannitol or xylitol protected the xylanase from thermal inactivation at 50°C. The protective effect by glycerol, xylitol and mannitol resulted in increases of 162, 262.5 and 150% when compared with the control at 120 min, approximately. Increasing the polyols concentration up to 20% (w/v) further improved the thermostability of xylanase after 120 min at 50°C by 300% when compared with the control (no additive). The kappa number reduced 2.56 points, which corresponds to 18.34 kappa efficiency. This xylanase is an attractive enzyme for potential future application in the pulp and paper industries, since industrial application requires a cellulase-free activity, maintenance of high temperature and enzyme stability are desirable. Key words: Aspergillus flavus, polyols, xylanase, biobleaching cellulose pulp.

Highlights

After cellulose, hemicellulose is the second most abundant renewable biomaterial available in nature and, among the hemicelluloses constituents, xylans are the major portion of the hemicellulose
Increasing the polyols concentration up to 20% (w/v) further improved the thermostability of xylanase after 120 min at 50°C by 300% when compared with the control
Maximum xylanase production was observed in wheat bran and sugarcane bagasse

Summary

Introduction

Hemicellulose is the second most abundant renewable biomaterial available in nature and, among the hemicelluloses constituents, xylans are the major portion of the hemicellulose. Xylan is a heteropolymer consisting principally of xylose and arabinose (Abdel-Sater and El-Said, 2001). A complex of enzymes are responsible for the hydrolysis of xylan, but the main enzymes involved are endo-1,4-β-xylanase and βxylosidase. These enzymes can be produced by bacteria, yeast or insect, but the principal commercial source is filamentous fungi (Biswas et al, 2010; Guimaraes et al, 2013a). A large number of different Aspergillus species have been reported as good producers of xylanases (Abdel-Sater and El-Said, 2001; Sandrim et al, 2005; Betini et al, 2009; Guimarães et al, 2013b)

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