Production and Properties of Thermostable Xylanase by Thermomyces lanuginosus NK-2 Grown on Lignocelluloses

Thermophilic Thermomyces lanuginosus NK-2, isolated from wheat straw compost, produced 1418 IU mL-1 of thermostable xylanase (EC 3.2.1.8) on Czapek`s basal medium containing wheat bran (2% w/v). The specific activity of NK-2 xylanase was found to be 1107 IU mg-1 of total protein. The fungus could also utilize different low-value agricultural residues and produce xylanase on corncobs (1004 IU mL-1), lentil bran (941 IU mL-1) and groundnut shells (355 IU mL-1). Supplementation of pure xylan (1% w/v) to wheat bran medium enhanced xylanase yield by 39% while other C-supplements repressed it. The xylanase was found to be active over a broad pH (4.0-9.0) and temperature range (25-85°C) and the pH and temperature optima were 5.0 and 6°C, respectively. It showed excellent thermal stability by retaining 83.4% activity after one hour of incubation at 6°C and its half-life at 7°C was 40 min. Presence of β-xylosidase (0.007 IU mg-1) was also noticed while CMCase and α-L-arabinosidase were not detected.