Purification and Characterization of Endo-β-1,4 Mannanase from Aspergillus niger gr for Application in Food Processing Industry

A thermostable extracellular β-mannanase from the culture
supernatant of a fungus Aspergillus niger gr was purified
to homogeneity. SDS-PAGE of the purified enzyme showed
a single protein band of molecular mass 66 kDa. The β-
mannanase exhibited optimum catalytic activity at pH 5.5
and 55oC. It was thermostable at 55oC, and retained 50%
activity after 6 h at 55oC. The enzyme was stable at a pH
range of 3.0 to 7.0. The metal ions Hg2+, Cu2+, and Ag2+
inhibited complete enzyme activity. The inhibitors tested,
EDTA, PMSF, and 1,10-phenanthroline, did not inhibit the
enzyme activity. N-Bromosuccinimide completely inhibited
enzyme activity. The relative substrate specificity of enzyme
towards the various mannans is in the order of locust
bean gum>guar gum>copra mannan, with Km of 0.11,
0.28, and 0.33 mg/ml, respectively. Since the enzyme is
active over a wide range of pH and temperature, it could
find potential use in the food-processing industry.