A peroxidase (DyP) involved in the decolorization of dyes and produced by the fungus strain Geotrichum candidum Dec 1 was purified. DyP, a glycoprotein, is glycosylated withN-acetylglucosamine and mannose (17%) and has a molecular mass of 60 kDa and an isoelectric point (pI) of 3.8. The absorption spectrum of DyP exhibited a Soret band at 406 nm corresponding to a hemoprotein, and its Na2S2O4-reduced form revealed a peak at 556 nm that indicates the presence of a protoheme as its prosthetic group. Nine of the 21 types of dyes that were decolorized by Dec 1 cells were decolorized by DyP; in particular, anthraquinone dyes were highly decolorized. DyP also oxidized 2,6-dimethoxyphenol and guaiacol but not veratryl alcohol. The optimal temperature for DyP activity was 30°C, and DyP activity was stable even after incubation at 50°C for 11 h.

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A fungus, Geotrichum candidum Dec 1, newly isolated as a dye-decolorizing microorganism, was used to decolorize molasses and an anthraquinone dye in shaken flasks. A degree of decolorization of molasses of 87% was achieved after 12 days of cultivation, and the maximum rate of decolorization of the dye in the culture broth was obtained in 7 days. The apparent activity of peroxidase in the molasses, which is responsible for dye decolorization, was significantly lower than that of purified peroxidase, due to the inhibition by molasses, but the inhibition was reduced after the fungus was fully grown. As two ultrafiltered fractions of molasses were similarly decolorized by Dec 1, Dec 1 apparently degraded colored substances of a wide range of molecular weights. When Dec 1 was cultivated in a medium in which sucrose in the molasses was hydrolyzed with invertase, the degree of decolorization of molasses, and rate of decolorization of the dye were similar to these obtained above.

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