Novel alkali-thermostable xylanase from Thielaviopsis basicola (MTCC 1467): Purification and kinetic characterization

A novel extracellular alkali-thermostable xylanase was purified to an apparent homogeneity from the submerged fermented culture filtrate of Thielaviopsis basicola MTCC 1467, wherein, the fungus was fed with rice straw as prime carbon source. SDS-PAGE analysis of the xylanase showcased molecular weight of similar to 32 kDa. This extracellular protein macromolecule had maximum xylanolytic activity at pH 5.5 and 60 degrees C, and was stable in the range of pH 5.0-10.0 for 5 days retaining >70% activity. The enzyme was stable at 30-50 degrees C for 5 h retaining >85% activity and further by retaining 70% activity at 60 degrees C for 2 h. The enzyme deactivation constants (k(d)) were in range of 0.41-1.3. The kinetic experiments specified that the enzyme had K-m and V-max values of 1.447 +/- 0.22 mg mL(-1) and 60.04+/-1.25 IU mL(-1), respectively, for xylan. The purified xylanase was significantly inhibited by Cu2+ and Zn2+ (similar to 58%), whilst Ca2+ and Na+ ions displayed partial inhibition (<8%) Intriguingly, the K+ and Mn2+ ions enhanced the activity by about similar to 10%. Both SOS and EDTA reduced its activity by 20%. (C) 2015 Elsevier B.V. All rights reserved.