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 2.5molL 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 24h 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±11.5Umg and high catalytic efficiency (1432.7±47.3Lmmols). 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 0.5molL 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.