An Eco-Friendly Production of a Novel and Highly Active Endo-1,4-beta-xylanase from Aspergillus clavatus

Abstract

Aims: Here, we describe a novel way to produce an endo-1,4-beta-xylanase from Aspergillus clavatus using paper and pulp industry waste. Methodology:  Optimal Aspergillus clavatus NRRL1 cultivation conditions were evaluated using minimal medium with different concentrations (1 to 10%) of paper sludge pretreated with HCl, during different periods (1 to 14 days), with different pH values (3.0; 3.5; 4.0; 4.5; 5.0; 5.5; 6.0; 6.5; 7.0; 7.5 and 8.0), different temperatures (25, 30, 35, and 40 ºC) and different mixing conditions (static and stirring). After that, the enzyme activity was determined by DNS (3,5-dinitrosalicylic acid), protein concentration was quantified by Bradford, SDS-PAGE was performed to evaluate the molecular mass, and TLC observed hydrolysis products. Results: The enzyme showed a molecular mass of 25 kDa, and its production has been highly improved by optimizing culture conditions. The best activity of this enzyme was obtained when A. clavatus was cultivated for 5 days, at 120 rpm, 5% paper sludge, pH 6.0, and 35 ºC. The degradation profile of the beechwood xylan by the crude extract containing the GH11 xylanase showed xylotriose as the main product, but xylotetraose and xylobiose were also produced in significant amounts. Conclusion: In addition to the fact that this xylanase has the property of producing large quantities of XOS (mainly xylotriose), it has the advantage of being obtained from recyclable waste of the pulp and paper industry. These facts confer great potential for future biotechnological and industrial applications.