Cloning, expression and characterization of C. crescentus xynA2 gene and application of Xylanase II in the deconstruction of plant biomass

• DOI: 10.1007/s11033-020-05507-2
• Publication Date: 2020-06-15T11:04:17Z
• Authors: Débora Jacomini; Larissa Bussler; Juliana Moço Corrêa; Marina Kimiko Kad...; Alexandre Maller; José Luis da-Conc...; Rita de Cássia Ga...
• Keywords: 0301 basic medicine; Endo-1,4-beta Xylanases; Hydrolysis; Temperature; Hydrogen-Ion Concentration; Chromatography, Affinity; Recombinant Proteins; Substrate Specificity; Kinetics; 03 medical and health sciences; Xylosidases; Caulobacter crescentus; Enzyme Stability; Xylans; Biomass; Cloning, Molecular

Biotechnology offers innovative alternatives for industrial bioprocesses mainly because it uses enzymes that biodegrade the hemicellulose releasing fermentable sugars. Caulobacter crescentus (C. crescentus) has seven genes responsible for xylanolytic cleavage, 5 to β-xylosidases (EC 3.2.1.37) and 2 for endoxylanases, like xynA2 (CCNA_03137) that encodes Xylanase II (EC 3.2.1.8) of the glycohydrolases-GH10 group. The xynA2 gene was amplified by PCR, cloned into the pTrcHisA vector e efficiently overexpressed in E. coli providing a His-tag fusion protein. Recombinant xylanase (XynA2) was purified by affinity chromatography using a nickel sepharose column and exhibited a single 43 kDa band on SDS-PAGE gel. XynA2 showed an optimum alkaline pH (8) and stability at alkaline pH for 24 h. Although C. crescentus is mesophilic, XynA2 has optimum temperature of 60 °C and is thermo-resistance at 65 °C. XynA maintains 66% of the enzymatic activity at high temperatures (90 °C) without being denatured.The enzyme displayed a xylanolitic activity free of cellulase to xylan from beechwood and it was not inhibited in the presence of 50 μmol mL-1 of xylose. In addition, dithiothreitol (DTT) induced XynA2 activity, as it improved its kinetic parameters by lowering the KM (5.78 μmol mL-1) and increasing the KCat/KM ratio (1.63 U s-1). Finally, C. crescentus XynA2 efficiently hydrolyzed corn straw with high release of reducing sugars that can be applied in different branches of the industry.