Degradation of xenobiotic compounds and dehalogenation by using multi enzyme systems of a newly isolated fungus, Geotrichum canididum Dec 1

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(1) The effluent from kraft pulp bleaching process was decolorized by G. canididum Dec 1 and the color removal ratio reached 70-80%. The decolorization process by Dec 1 consists of two steps, namely the first adsorption of color substances to the surface of the cells and the second biodegradation by the cells. Simultaneously, the absorbable organic halogens (AOX) that correspond to the aromatic compounds containing halogen was reduced by 43%, indicating that Dec 1 conducted dehalogenation in parallel to decolorization of lignin in the effluent.(2) The effluent from oxygen-delignified process was decolorized by Dec 1 and the color removal ratio reached 90%. Bioleaching of oxygen-delignified pulp was carried out by the culture broth of Dec 1 and the brightness of the pulp increased 30 points and the kappa number decreased by 10 points. After the effluent was decolorized by Dec 1, the effluent was mixed with the pulp and the bleaching was continued. As the brightness of the pulp increased … More significantly, Dec 1 showed potential of consecutive treatment of the effluent and the bleaching of the pulp.(3) Bleaching of unbleached kraft pulp was tried by using the culture of Dec 1. The increase in brightness and the reduction of the kappa number were almost equivalent to or more than those of well-studied basidiomycetes. After the unbleached kraft was bleached by Dec 1, the pulp was washed and mixed with the freshly grown Dec 1 culture and the second bleaching was continued. The increase in brightness reached 50 points and this values demonstrate the usefulness of the bio-bleaching of the pulp by Dec 1.(4) Peroxidase (DyP) and manganese peroxidase (MnP) were purified from the culture broth of Dec 1. As the activities of DyP an MnP were detected during decolorization of oxygen-delignified effluent, bleaching of oxygen-delignified pulp and bleaching of unbleached kraft pulp, the two enzymes are found to be heavily involved in those reactions. The higher activity of MnP in the degradation of lignin was newly found.(5) Lignin-degradation ability of Dec 1 was confirmed by the plate test and by the liquid culture using commercial lignin. The color of lignin changed from brown to yellow in plate test. It was confirmed by gel chromatography that the average molecular mass of the original lignin, 80,000 was reduced to less than 3,000. As the activities of DyP and MnP were detected, this is the first report that the existence of two enzymes involved in lignin degradation was found other than basidiomycetes. The degradation of the dye, Poly R-478 by the two enzymes was also clarified. Less