Purification and characterization of endo-Beta-1,4 mannanase from Aspergillus niger gr for application in food processing industry

Abstract

A thermostable extracellular ?-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 ?-mannanase exhibited optimum catalytic activity at pH 5.5 and 55°C. It was thermostable at 55°C, and retained 50% activity after 6 h at 55°C. The enzyme was stable at a pH range of 3.0 to 7.0. The metal ions Hg 2+, 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. © The Korean Society for Microbiology and Biotechnology.