Production, purification, and properties of glucose oxidase from the biocontrol fungus Talaromyces flavus
Talaromyces flavus produces the enzyme glucose oxidase, which may be involved in biocontrol of the fungal plant pathogen, Verticillium dahliae. A strain of T. flavus was selected from the wild-type population for the production of extracellular glucose oxidase, and the enzyme was purified by a combination of acetone precipitation and high performance liquid chromatography (HPLC). Approximately 12–25 mg of pure protein was obtained from 2 L of culture, and the total recovered activity ranged from 5 to 10 × 103 μmol/min. Homogeneity of the purified enzyme was demonstrated by HPLC and by native and sodium dodecylsulfate polyacrylamide gel electrophoresis. Molecular weight of the native enzyme was 164 000 and that of the subunit was71 000, which indicated that the native enzyme is a dimer. The apparent Km value for D-glucose was 10.9 mM. The optimum pH for the enzyme activity was 5.0, but the enzyme was stable in buffer from pH 3 to 7. The enzyme was observed to be a glycoprotein, and amino acid analysis of the purified enzyme indicated a similarity to glucose oxidases from fungal sources. Isozymes of the enzyme with pI values of 4.40–4.55 were detected on analytical isoelectric focusing gels. Key words: antibiosis, biocontrol, glucose oxidase, Talaromyces flavus.