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 50°C in pH 5.0–5.5 for Xyl I and 5.5 for Xyl II. The xylanases were very stable at 40°C and
in the pH ranges from 4.5–6.5 for Xyl I and 4.0–8.0 for Xyl II. The ion Hg
2+ 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 2680.2 and 462.2 U·mg of protein
-1 (Xyl I) and 10.7, 4.0 mg·mL
-1
and 4553.7 and 1972.7 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.
Conclusions: The enzymes present potential for application in industrial processes that require activity in acid
conditions, wide-ranging pH stability, such as for animal feed, or juice and wine industries.