PURIFICATION AND CHARACTERIZATION OF β-D-GLUCOSIDASE FROM ASPERGILLUS NIGER NARINGINASE

ABSTRACT β-D-glucosidase has been purified from naringinase of Aspergillus niger to homogeneity by ammonium sulfate fractionation and chromatographies on diethylaminoethyl Sepharose, phenyl-Sepharose and Sephacryl S-200 HR, with the aid of prunin used as a specific substrate to detect the β-D-glucosidase activity by a high-performance liquid chromatography method. The molecular weight of the β-D-glucosidase was determined to about 100 kDa by exclusive gel chromatography and sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis analysis. Optimal pH and stable pH range of the enzyme were 4.5–5 and 3.5–8.0, respectively. Its optimal temperature was in the range of 55–60C. The enzyme was strongly inhibited by 1 and 5 mM of Fe2+, Fe3+, Zn2+, Al3+, Mn2+, Cu2+, Ag+ and Hg2+ ions and SDS. This β-D-glucosidase had a higher specific affiliation to prunin than p-nitrophenyl-β-D-glucopyranoside. Its Km and Vmax toward prunin were 2.59 mM and 18.76 U/mg. PRACTICAL APPLICATIONS This paper mainly focused on the purification and characterization of the β-D-glucosidase from the enzyme complex naringinase, which was prepared from a fermented broth of Aspergillus niger. To our knowledge, it is the first successful attempt to purify and characterize the β-D-glucosidase from this naringinase, which is considered safe for food use. This study can help interested readers to take further insights into naringinase from A. niger and set strong base for the production and industrial applications of the β-D-glucosidase, which is useful to debitter citrus juice and produce medical ingredients.