A halotolerant bifunctional β-xylosidase/α-l-arabinofuranosidase from Colletotrichum graminicola: Purification and biochemical characterization

A β-xylosidase from Colletotrichum graminicola (Bxcg) was purified. The enzyme showed high halotolerance, retaining about 63% of the control activity in the presence of 2.5 mol L−1 NaCl. The presence of NaCl has not affected the optimum reaction temperature (65 °C), but the optimum pH was slightly altered (from 4.5 to 5.0) at high salt concentrations. Bxcg was fully stable at 50 °C for 24 h and over a wide pH range even in the presence of NaCl. In the absence of salt Bxcg hydrolyzed p-nitrophenyl-β-d-xylopyranoside with maximum velocity of 348.8 ± 11.5 U mg−1 and high catalytic efficiency (1432.7 ± 47.3 L mmol−1 s−1). Bxcg revealed to be a bifunctional enzyme with both β-xylosidase and α-l-arabinofuranosidase activities, and hydrolyzed xylooligosaccharides containing up to six pentose residues. The enzyme showed high synergistic effect (3.1-fold) with an endo-xylanase for the hydrolysis of beechwood xylan, either in the absence or presence of 0.5 mol L−1 NaCl, and was tolerant to different organic solvents and surfactants. This is the first report of a halotolerant bifunctional β-xylosidase/α-l-arabinofuranosidase from C. graminicola, and the enzyme showed attractive properties for application in lignocellulose hydrolysis, particularly under high salinity and/or in the presence of residues of pretreatment steps.