Comparison of kinetic characteristics of xylanases from <i>Aspergillus niger<i> and <i>Trichoderma</i> sp. with pH and temperature baking process parameters

Abstract

Arabinoxylans are the predominant non-starch polysaccharides of the cell walls of wheat grain, and can contribute up to 3% of the total polysaccharide content of the flour. Endo-(1-4)-β-xylanase is able to hydrolyze the glycosidic bonds between two xylose units in the xylan backbone during baking process. The use of xylanases in the baking process leads to changes in the rheology of the dough. The aim of this work was to establish the best enzymatic hydrolysis conditions. The results suggest that the pure xylanase from Aspergillus niger needs less substrate to achieve maximum velocity (V_max). However the xylanase from Trichoderma sp. has a higher V_max apparent which means that it needs less time to convert the substrate into products. The xylanase from A. niger presented 50°C as its optimum temperature, 40% residual activity at 25°C and 80% at 36°C. The xylanase from Trichoderma sp. presented 50°C as its optimum temperature, 20% residual activity at 25°C and 60% at 36°C, which could be evidence that this enzyme is less active than the xylanase from A. niger. Moreover, the xylanase from Trichoderma sp. presented 90% residual activity in the baking process pH range, indicating that this enzyme can be more effective in the dough making process. The catalytic reactions of both enzymes are endothermic due to positive enthalpy and they are favourable process because the both Gibbs free energy were negative.

Keywords: Xylanase, baking, enzyme, Trichoderma sp., Aspergillus niger