Background: Two xylanases, Xyl I and Xyl II, were purified from the crude extracellular extract of a Trichoderma inhamatum strain cultivated in liquid medium with oat spelts xylan.

Results: The molecular masses of the purified enzymes estimated by SDS-PAGE and gel filtration were, respectively, 19 and 14 kDa for Xyl I and 21 and 14.6 kDa for Xyl II. The enzymes are glycoproteins with optimum activity at 50ºC in pH 5.0 - 5.5 for Xyl I and 5.5 for Xyl II. The xylanases were very stable at 40ºC and in the pH ranges from 4.5 - 6.5 for Xyl I and 4.0 - 8.0 for Xyl II. The ion Hg²⁺ and the detergent SDS strongly reduced the activity while 1,4-dithiothreitol stimulated both enzymes. The xylanases showed specificity for xylan, K_m and V_max of 14.5, 1.6 mg ^● mL^-1 and 2,680.2 and 462.2 U ^● mg of protein^-1 (Xyl I) and 10.7, 4.0 mg ^● mL^-1 and 4,553.7 and 1,972.7 U ^● mg of protein^-1 (Xyl II) on oat spelts and birchwood xylan, respectively. The hydrolysis of oat spelts xylan released xylobiose, xylotriose, xylotetrose and larger xylooligosaccharides.