Purification and characterization of xylanases from Trichoderma inhamatum

ABSTRACT

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 Hg2+ and the detergent SDS strongly reduced the activity while 1,4-dithiothreitol stimulated both enzymes. The xylanases showed specificity for xylan, Km and Vmax 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.