Comparison of properties and mode of action of six secreted xylanases from Chrysosporium lucknowense

Eight homogeneous xylanases were purified from crude multienzyme preparations produced by various mutant strains of the fungus Chrysosporium lucknowense. Peptide mass fingerprinting showed that the isolated enzymes are the products of six different genes of C. lucknowense, three of them encoding xylanases belonging to family 10 of glycoside hydrolases (GH) and three other genes encoding enzymes of the GH11 family. Intact Xyn10A and Xyn10B possessed a family 1 CBM at the N- and C-terminus, respectively; each of the enzymes was also isolated in the form without CBM. The GH11 family xylanases displayed very high specific activities against various xylans, the Xyn11A being the most active (329–494 U mg−1). In hydrolysis of glucuronoxylan and arabinoxylan, xylanases belonging to the same family were characterized by very similar kinetic behavior and composition of the final products. The GH10 family xylanases showed greater catalytic versatility and formed shorter oligosaccharides than those of family 11. Xyn10A, Xyn10B and Xyn11A were characterized by broad pH optima and displayed high activity in neutral and moderate alkaline medium. The GH10 family xylanases demonstrated high thermostability retaining more than 70% of activity after 1-h incubation at 60 °C. These properties make the C. lucknowense xylanases promising candidates for different biotechnological applications.