Production of a new D-amino acid oxidase from the fungus Fusarium oxysporum

Abstract

The fungus Fusarium oxysporum produced a D-amino acid oxidase (EC 1.4.3.3) in a medium containing glucose as the carbon and energy source and ammonium sulfate as the nitrogen source. The specific D-amino acid oxidase activity was increased up to 12.5-fold with various D-amino acids or their corresponding derivatives as inducers. The best inducers were D-alanine (2.7 μkat/g of dry biomass) and D-3-aminobutyric acid (2.6 μkat/g of dry biomass). The addition of zinc ions was necessary to permit the induction of peroxisomal D-amino acid oxidase. Bioreactor cultivations were performed on a 50-liter scale, yielding a volumetric D-amino acid oxidase activity of 17 μkat liter-1 with D-alanine as an inducer. Under oxygen limitation, the volumetric activity was increased threefold to 54 μkat liter-1 (3,240 U liter-1).