The pH stability of xylanase was assessed at a pH ranging 4.0–
12.0 at 60 C after 30 min incubation. To determine the thermostability
of xylanase activity, the xylanase was incubated at different
temperatures (60–80 C) in the absence of substrate. After incubating
for 1 h, the residual xylanase activity was determined at 70 C
for 10 min (Bailey et al., 1992). Additionally, the effects of various
reagents (0.01 M) on xylanase activity were determined by preincubating
the enzyme with individual reagents in 0.05 M
glycine/NaOH (pH 8.0) at 30 C for 30 min. Activities were then
measured at 70 C for 10 min in the presence of the metal ions or
reagents. The activity assayed in the absence of reagents was recorded
as 100%. Finally, the kinetic constants Km and Vmax were
determined following the method of Lineweaver and Burk (Bajpai,
1997; Gupta et al., 2000).