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

Abstract

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 degrees 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.

Enhanced thermal stability and pH behavior of glucose oxidase on electrostatic interaction with polyethylenimine

“…At a pH range between 5 and 11, GOx formed a complex with PEI. Maximum activity for GOx, both in complex and in its free form, was reached at around pH 5 as reported in the literature [38]. Complex formation at pH 5-11 led to the disappearance of the FAD peak that could be interpreted as a decrease in the exposure of the active site of GOx-a consequence of the configuration it acquires when in complex with PEI.…”

Thermostability and thermodynamic characterization of sprouted pearl millet ?-amylases for its biotechnological applications

“…The high values of the change in enthalpy of denaturation obtained for thermoinactivation of the α-amylases from pearl millet indicated that the enzyme would undergo a considerable change in conformation during denaturation (Marin et al, 2003). The fact that ΔH values decreased with increase in temperature reveals that less energy is required to denature the enzyme at high temperature (Bhatti et al, 2006). A similar trend in the values of ΔH was observed in peroxidase from white yam (Eze et al, 2010) though with different magnitude, α-amylase from digestive tract of tropical house cricket (Kouadio et al, 2013), α-amylase from sorghum bicolar (Kumar, 2008).…”

Offline glucose biomonitoring in yeast culture by polyamidoamine/ cysteamine‐modified gold electrodes

“…changes between a wide range of 1.59-130 mM for beta-D-glucose. [48][49][50][51][52] Also the free form of pyranose oxidase from Cariolus hirsutus and Cariolus versicolor sp. has K M values 0.83 and 1.7 for D-glucose, respectively.…”