Characterization of crude xylanase produced by A. lentulus
The pH and thermal stabilities of cellulase-free xylanases are
important attributes for their potential industrial applications. The
crude xylanase enzyme obtained from A. lentulus was characterized
for its optimal pH and temperature range. The relative xylanase
activities obtained at different pH ranges (4e10) are presented in
Fig 3a. The pH was adjusted with 0.5 M citrate buffer (pH 4e6) or
0.5 M phosphate buffer (pH 7e10). The highest xylanase activity
was reported at pH 5 which reduced to 92% at pH 4. The decline in
enzyme activity was marginal till neutral pH range (91.6% residua activity at pH 7) however; it declined sharply in alkaline pH ranges
with 38.5% activity at pH 10 where statistically significant differences
were observed at p 0.05. Although a sharp decline at
alkaline pH was observed in the xylanase activity, still 77.2% and
59.1% activity was retained at pH 8 and pH 9 which is the prevailing
pH during the bleaching process of the pulp. The pH stability profile
for crude xylanase is represented in