Cellobiose dehydrogenase (CDH) is produced as an extracellular enzyme by many fungal species grown on cellulose and plant biomass. CDH is the flavoheme enzyme which oxidizes the end group of cellobiose to form the lactone via extraction of two electrons from the substrate to an appropriate electron acceptor. We investigated the electron transfer mechanism during the catalytic cycle of CDH and clarified a sophisticated regulatory function of cellobiose metabolism involving the interaction between the flavin and heme of CDH. In addition to its catalytic activity, CDH can bind to the amorphous surface of cellulose. These properties of CDH are important for understanding the fungal system of cellulose degradation and useful for application of CDH. We have developed a method for real-time and sensitive detection of cellulase activity using a CDH catalytic system and a method for surface analysis of cellulosic materials based on the evaluation of CDH adsorption.

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Degradation of dibenzo p-dioxin (DD) by an edible ectomycorrhizal mushroom, Lyophyllum shimeji, was examined. DD was degraded by treatment with L. shimeji, resulting in the metabolite monohydroxylated DD. DD degradation was significantly inhibited by the addition of cytochrome P450 monooxygenase inhibitors and inhibited by the generation of hydroxylated DD. These results suggest that L. shimeji can metabolize DD to a monohydroxylated compound, most likely mediated initially by the cytochrome P450 system. This is the first report of an ectomycorrhizal fungus with the ability to metabolize DD.

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We purified and characterized extracellular β-glucosidase of the Tricholoma matsutake J-1 strain isolated from hardwood forest (Quercus sp.). The purified enzyme was obtained from about 0.76l static culture filtrate, with 17.7% recovery and a single band on SDS-PAGE. The enzyme displayed the most activity around 60℃ and pH4.0. The activity of this enzyme against cello-oligosaccharides as a substrate was higher than that of the T. matsutake Z-1 strain isolated from softwood (Pinus densiflora). Furthermore, the enzyme activity increased with an increase in the number of β-1,4 glucosidic bonds.

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Light and electron microscopic observations were made on ectomycorrhizae aseptically synthesized between Rhizopogon roseolus (shoro) and Pinus thunbergii. Initial mycorrhizal formation could be observed within 2 weeks after inoculation with mycelial plugs. Typical dichotomous ectomycorrhizae and extraradical mycelia were clearly detectable in P. thunbergii seedlings 8 weeks after inoculation. Light microscopy of semi-thin sections revealed multi-branched structures of the Hartig net and polyphenolic inclusions in the inner mantle layers, while transmission electron microscopy of thin sections revealed dense cytoplasmic cells in the mantle and Hartig net hyphae. At the interface between the host cortical cell and the multi-branched Hartig net, the host and fungal cell walls were fused and became indistinguishable forming a characteristic involving layer. Intercellular hyphae presented many aberrant mitochondria, whereas host cortical cells included typical mitochondria. Particularly elongated mitochondria were detected in the multi-branched Hartig net.

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Sake lees were fermented with mushroom to add high antioxidant activity. During fermentation with mushroom, sake lees increased their antioxidant activity and brown color. The pigment was analyzed by time-of-flight mass spectrometry. The main compound that had increased by fermentation was determined to be C_<18>H_<14>O_5. As sake lees are made from rice, it was speculated that this main compound had two dehydrated p-coumaric acids.

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