Purification and thermodynamic characterization of glucose oxidase from a newly isolated strain of Aspergillus niger

• Published in: Canadian journal of microbiology Vol. 52; no. 6; pp. 519 - 524
• Main Authors: Bhatti, H.N, Madeeha, M, Asgher, M, Batool, N
• Format: Journal Article
• Language: English
• Published: Ottawa, Canada NRC Research Press 01.06.2006; Canadian Science Publishing NRC Research Press
• Subjects: Ammonium; Aspergillus; Aspergillus niger; Aspergillus niger - enzymology; Aspergillus niger - isolation & purification; Aspergillus niger - metabolism; Biosensors; Body fluids; Chemical properties; Chemicals; Defense mechanisms; Diagnostic tests; enzyme activity; enzyme kinetics; Enzyme Stability; Enzymes; Food; Fruit juices; glucose; glucose oxidase; Glucose Oxidase - chemistry; Glucose Oxidase - isolation & purification; Glucose Oxidase - metabolism; heat stability; Hydrogen-Ion Concentration; Kinetics; Microbiology; oxidation; Plant pathology; purification; Strain; Temperature; thermal stability; Thermodynamics
• ISSN: 0008-4166; 1480-3275
• DOI: 10.1139/w05-158

An intracellular glucose oxidase (GOD) was isolated from the mycelium extract of a locally isolated strain of Aspergillus niger NFCCP. The enzyme was partially purified to a yield of 28.43% and specific activity of 135 U mg -1 through ammonium sulfate precipitation, anion-exchange chromatography, and gel filtration. The enzyme showed high specificity for D-glucose, with a K m value of 25 mmol L -1 . The enzyme exhibited optimum catalytic activity at pH 5.5. Optimum temperature for GOD-catalyzed D-glucose oxidation was 40 °C. The enzyme displayed a high thermostability having a half-life (t 1/2 ) of 30 min, enthalpy of denaturation (H*) of 99.66 kJ mol -1 , and free energy of denaturation (G*) of 103.63 kJ mol -1 . These characteristics suggest that GOD from A. niger NFCCP can be used as an analytical reagent and in the design of biosensors for clinical, biochemical, and diagnostic assays.Key words: glucose oxidase, Aspergillus niger, kinetics, thermodynamics, thermal stability.