Bioprocess and biotecnology: effect of xylanase from Aspergillus niger and Aspergillus flavus on pulp biobleaching and enzyme production using agroindustrial residues as substract

Abstract

This study compares two xylanases produced by filamentous fungi such as A. niger and A. flavus using agroindustrial residues as substract and evaluated the effect of these enzymes on cellulose pulp biobleaching process. Wheat bran was the best carbon source for xylanase production by A. niger and A. flavus. The production of xylanase was 18 and 21% higher on wheat bran when we compare the xylanase production with xylan. At 50°C, the xylanase of A. niger retained over 85% activity with 2 h of incubation, and A. flavus had a half-life of more than 75 minutes. At 55°C, the xylanase produced by A. niger showed more stable than from A. flavus showing a half-life of more than 45 minutes. The xylanase activity of A. niger and A. flavus were somehow protected in the presence of glycerol 5% when compared to the control (without additives). On the biobleaching assay it was observed that the xylanase from A. flavus was more effective in comparison to A. niger. The kappa efficiency corresponded to 36.32 and 25.93, respectively. That is important to emphasize that the cellulase activity was either analyzed and significant levels were not detected, which explain why the viscosity was not significantly modified.

Keywords: Agroindustrial residues; Aspergillus flavus; Aspergillus niger; Biobleaching; Wheat bran.

Figure 1

Characterization of the xylanases fromA. nigerandA. flavus. Thermostability of the xylanase of A. niger(A) and A. flavus(B) were determined using McIlvaine buffer pH 5.0 at 60°C after incubating the enzymes on temperatures of 45 (■), 50 (●) and 55°C (▲). Thermostability of the xylanases at 55 (A. niger) (C) and 50°C (A. flavus) (D), without additives (■), and with 5% glycerol (●) and polyethyleneglycol (▲). pH stability of A. niger(E) and A. flavus(F) were determined incubating both enzymes at different pHs (3.0 - 8.0) at 0°C, during 1 hour and after the residual activities were determined at 60°C, pH 5.0.