Thesis (M.Sc.) - Cairo University - Faculty of Science - Department of Biochemistry

Aspergillus niger was isolated and purified from soil. The result of the preliminary experiment revealed that A. niger was a good producer of extracellular naringinase enzyme in the medium. Statistical experiment was used for optimization of narigniase enzyme using orange peel as enzyme inducer, which was resulted 18 different media with different compositions. The medium number 15 gave highest enzyme activity (1.2 U/ml) with relatively low protein concentration (1.6 mg/ml), it was selected for the large scale production of nariginase. The fractional precipitation with ammonium sulfate (65%) step yielded enzyme activity (2930 U/ml), while the recovery was (55%) with purification fold (5.8), further purification on DEAE Sephadex column yielded enzyme activity (1395 U/ml), while the recovery was (26%) with purification fold (9). The molecular weight was determined on SDS-PAGE, which showed one band at 80 kDa. The optimum temperature and pH for naringinase activity were 40{u00B0}C and 4.0. The enzyme was stable at pH 4.0 and thermally at 40{u00B0}C and 50{u00B0}C. Zn²⁺ was the best metal ion for enhancement of naringinase activity, while Co²⁺ showed high inhibitory effect. The EDTA and other metal (Mg²⁺, Ca²⁺, Mn²⁺, Cu²⁺ and Hg²⁺) showed significant influence on naringinase activity.

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