Background: Bacillus subtilis
UMC7 isolated from the gut of termite Macrotermes malaccensis
has the ability to
secrete a significant amount of extracellular endoglucanase, with an enzyme activity of 0.12 ± 0.01 μmol/min/
mL. However, for economically viable industrial applications, the enzyme needs to be expressed in a
heterologous host to overcome the low enzyme production from the wild-type strain.
The endoglucanase gene from B. subtilis
UMC7 was successfully cloned and expressed. A higher
enzyme activity was observed in the intracellular fraction of the recombinant clone (0.51 ± 0.02 μmol/
min/mL) compared with the cell-bound fraction (0.37 ± 0.02 μmol/min/mL) and the extracellular fraction
(0.33 ± 0.01 μmol/min/mL). The recombinant endoglucanase was approximately 56 kDa, with optimal
enzyme activity at 60°C and pH 6.0. The activity of the enzyme was enhanced by the addition of Ca2+
However, the enzyme was inhibited by other metal ions in the following order:
. The enzyme was able to hydrolyze both
low- and high-viscosity carboxymethyl-cellulose (CMC), avicel, cotton linter, filter paper and avicel but not
starch, xylan, chitin, pectin and p-nitrophenyl α-D-glucopyranoside.
The recombinant endoglucanase showed a threefold increase in extracellular enzyme activity
compared with the wild-type strain. This result revealed the potential of endoglucanase expression in E. coli
which can be induced for the overexpression of the enzyme. The enzyme has a broad range of activity with
high specificity toward cellulose.