During industrial application, whole cells are usually used as
the source of enzymes but the efficiency can be improved by using
purified enzymes or by excluding certain other unwanted enzymes
(Bajpai, 1997). The crude xylanase from culture OM3 can be partially
purified 2.6-fold with a yield of 67.2% by ammonium sulfate
fractionation (30–70% saturation) and following by dialysis with
glycine NaOH buffer (pH 8.0). After applying the precipitated
xylanase to agar plates containing birchwood xylan, the appearance
of more clear zones also suggests higher hemicellulose hydrolysis
activity. This xylanase was active between pH 5.0–9.0 and
retained more than 80% of its activity while exhibiting an optimum
pH ranging from 5.0 to 8.0 by retaining almost 100% activity at
60 C for 0.5 h. The enzyme activity beyond this range dropped
dramatically, for example, only 54% and 46% activity was retained
at pH 4.0 and 10.0, respectively. The optimum temperature for
hydrolysis reactions was 70 C (with a reaction time of 10 min)
with 77% and 70% of the maximum activity at 50 C and 80 C,
respectively. The enzyme activity kept increasing with an increase
in temperature from 40 C to 70 C but further increase in temperature
adversely affected the enzyme activity. Since utilization of
enzymes in industrial applications often encounters its thermal
inactivation, thermostability studies were carried out by pre-incubating
the enzyme up to 1 h in a temperature range of 60, 70 and
80 C. The xylanase from culture OM3 could retain 100% activity at
60 C after 1 h of incubation while still exhibited nearly 71% and
49% of its maximum activity after incubation of 1 h at 70 C and
80 C, respectively. The utilization of thermostable xylanase in
industry could improve the technical and economic feasibility of
industrial processes (Bajpai, 1997).