Purification and Characterization of Glucosamine Oxidase from Aspergillus Terreus NUK-1204 for Production of Glucosaminic Acid

Abstract

D-Glucosaminic acid (2-amino-2-deoxy-D-gluconic acid) is a valuable glucosamine derivative from the oxidation of the glucosamine (2-amino-2-deoxy-D-glucose). It can be produced via the fermentation of certain microorganisms, which involves complicated purification task, though. In an attempt to find an enzyme suited to glucosaminic acid production, the study presented a purified homogeneous glucosamine oxidase deriving from the wheat bran culture of a soil-isolated fungal strain, Aspergillus terreus NUK-1204. Maximum activity was observed in the wheat bran solid culture after five days of NUK-1204 growth, following its release from cells at 0.011 unitmL -1culture filtrate. The new kind of oxidase comprises a single polypeptide chain with a molecular mass of 54 kDa, containing FAD and exhibiting absorption maxima at 274, 372 and 439 nm. The enzyme was stable in 4.5-11 pH range, with an optimal reaction pH at 10.5 and optimal reaction temperature at 30°C. It remained stable at 20-50°C for 1 hr. The relative activity of glucosamine oxidase towards glucosamine and N-acetyl-glucosamine was 100:7, demonstrating high substrate specificity. It doesn’t inhibit glucosamine. To the best of our knowledge, this is the first report ever on the discovery of a glucosamine oxidase based on enzyme substrate specificity.