We conducted chemical and biochemical studies on mushrooms, and gave the following results. 1. Compounds that are effective for dementia were isolated from Yamabushitake (Hericium erinaceus) and Bunahariatake (Mycoleptodonoides aitchisonii). Regarding Yamabushitake, our research triggered some clinical trials, and improvement effects on dementia were found. 2. Anti-MRSA (methicillin-resistant Staphylococcus aureus) compounds were found out from Yamabushitake and Hanabiratake (Sparassis crispa). 3. Hyaluronan degradation regulating compounds were obtained from Keshoshimeji (Tricholoma orirubens) and Shironumeriiguchi (Suillus laricinus). 4. Gastrointestinal toxic compounds were obtained from Kakishimeji (Tricholoma ustale) and Dokuyamadori (Neoboletus venenatus). 5. Compounds that cause clinical deterioration from drinking were found form Hoteishimeji (Clitocybe clavipes). 6. As studies on lectin, a lectin having food suppression activity was purified from Hiratake (Pleurotus ostreatus). A lectin from Yamabusitake is the first sialic acid specific lectin isolated from other than animals. An N-glycolylneuraminic acid-binding lectin was discovered from Ohshirokarakasatake (Chlorophyllum molybdites) and this is the first lectin showing such sugar binding specificity.

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Brown blotch is a serious bacterial disease affecting mushroom production. The causal agent, Pseudomonas tolaasii, secretes tolaasins, lipodepsipeptide toxins that cause browning of fruiting bodies in a broad range of mushrooms. In this study, to develop biological control agents for bacterial brown blotch on mushrooms, we evaluated the bacterial flora of shiitake fruiting bodies and isolated tolaasin detoxifying bacteria. The culturable flora on fruiting bodies of shiitake consisted of various bacteria, and were stable during shiitake cultivation. Tolaasin detoxifying bacteria, consisting of Bacillus sp., Leifsonia sp., Microbacterium sp., Paenibacillus sp., Plantibacter sp., Pseudoxanthomonas sp., Sphingobacterium sp., and Streptomyces sp., were isolated from shiitake fruiting bodies. Analysis of the mechanism of tolaasin detoxification by Pseudoxanthomonas spp. suggested that tolaasin detoxifying ability is widely distributed in Pseudoxanthomonas spp.

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The cDNA encoding a major laccase isozyme (Lac1) produced by Grifola frondosa in culture fluid was cloned. The lac1 cDNA encodes a mature Lac1 of 499 amino acid residues, preceded by a signal peptide with 21 amino acid residues. The lac1 cDNA was expressed in Pichia pastoris. The recombinant Lac1 (rLac1) was produced as a secreted protein with its own signal peptide. The addition of CuSO4 to the culture medium was effective in increasing laccase activity. The molecular mass of purified rLac1 was estimated to be 95 kDa, which is greater than that of the native form, suggesting that rLac1 is highly glycosylated. The catalytic efficiency (kcat/Km) of rLac1 was lower than that of native Lac1 (nLac1) for all substrates tested. However, rLac1 exhibited higher thermostability and stability in acidic conditions compared to nLac1. In addition, rLac1 showed a high capacity for decolorization of several synthetic dyes comparable to nLac1. These results demonstrated the higher application potential of rLac1 than that of nLac1.

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Rings or arcs of fungus-regulated plant growth often occur on lawns and golf courses, and are commonly called “fairy rings”. The rings are produced by the interaction between grasses and fungi. We investigated the possibility of specific mycelial growth regulator(s) produced by a grass, Agrostis stolonifera (bentgrass). We succeeded in the isolation and purification of an active compound from the bentgrass. The active compound was identified as 2-acetyl-3, 5-dimethoxyphenol by interpretation of NMR and mass data. This compound inhibited mycelial growth of a fairy ring-forming fungus, Lepista sordida, and two basidiomycetes, Flammulina velutipes and Coprinopsis cinerea.

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Shiitake cultivation is being done even in areas affected by radioactive contamination. When using logs in this area, only three trees are inspected before cutting the wood. The results are used to estimate the level of contamination in the log. We compare the results obtained to the index value prior to cutting the wood. Despite these tests, hodagi with high radiocesium concentration and fruit bodies with high radiocesium concentration are often found by a later check. Therefore, as a result of investigating these production lots, wood that exceeded the index value was included. It is rare for hodagi to get contaminated during indoor Shiitake cultivation. It was thought that these hodagi already had a high radiocesium concentration before use in Shiitake cultivation. In sample inspection, there is a possibility that some logs contain higher radiocesium concentration than the results obtained from analysis of test logs. Reliable inspections to eliminate these logs are needed when using trees cut from radioactively contaminated areas. Although the transition coefficient of radiocesium from hodagi to shiitake mushrooms is set at 2.0, it was considered necessary to continue investigation.

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