Mycelial growth of Lentinula edodes (shiitake, pyogo) was examined in a sawdust-based substrate under four moisture contents: 43, 55, 64 and 69% with various strain types. The moisture content significantly affected mycelial growth and primordial formation but the water effects differed depending upon the fungal strains. Moisture content at 43% significantly reduced mycelial growth, but Sanrim No. 6 strain was less affected by the moisture content than others were. The mycelial growth of Sanrim No. 4 decreased at both 43 and 69% moisture contents. Moisture content at 64% was the best for mycelial growth and substrate decomposition. The trend of dry weight loss due to the decomposition was similar to that of mycelium growth. However, primordial formation was neither related to the mycelial growth nor to the decomposition. The moisture content of 69% dramatically increased the primordial formation, but the effect differs among the strains. Ergosterol content of the sawdust-based culture was higher at 55 and 64% than at 43 and 69% moisture content levels. The primordial formation was not related to the ergosterol content. This study clearly showed that the moisture content differently affected mycelial growth and primordial formation depending on L. edodes strains.

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Six strains of Grifola frondosa (Maitake) were tested for an antimutagenic effect against EMS (ethyl methanesulfonate) using Salmonella typhimurium TA100. The boiled water extract of G. frondosa fruit-bodies in Sample H (Hokuto strain) presented the highest effects against EMS. The remaining mutagenicity in 1.0 mg/plate of the G. frondosa from Hokuto was observed to be about 50%. Compared to the antimutagenicity of vegetables and fruits, the antimutagenicity of mushrooms showed to be weaker. In order to study the mechanisms, we examined antimutagenicity and bio-antimutagenicity against EMS using the commercial β-1, 3 glucan reported as a main substance having antitumorigenesis and anticarcinogenesis. The β-1, 3 glucan was observed to exhibit both moderate antimutagenicity and bio-antimutagenicity. It was possible that a complex was formed between the β-1, 3 glucan and EMS. We also estimated that the bioantimutagenic effect caused the excision of methylation in DNA and results in excision repair.

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Bed-logs for the Shiitake (Lentinula edodes) mushroom cultivation were inoculated with the suspension of Graphostroma platystoma ascospore using various inoculation methods. The rate of stroma formation in each method was evaluated to elucidate the location of the invasion of G. platystoma in the bed-logs [the rate of stroma formation (=stroma rate): a ratio of areas with stromata to total surface area of the bed-logs]. Wounds inflicted through bark to sapwood are required for the ascospores to invade the bed-logs. The relation between the timing of inoculation with the ascospores and the rate of stroma formation was also examined. A high rate of stroma formation was scored when bed-logs were inoculated with the ascospores one month before the inoculation of the Shiitake spawn or simultaneous inoculation with the spawn. However, the rate of stroma formation was low when the ascospores were inoculated two months after the inoculation with the spawn. These results suggest that the ascospores invade bed-logs during early periods of inoculation season of the Shiitake spawn. After the inoculation of the ascospores to live Quercus acutissima trees in the spring, the trees were cut down during winter of the same year, inoculated with the Shiitake spawn and incubated in a standard cultivation protocol. In this case the high rate of stroma formation in the bed-logs was observed. These results suggest that the ascospores are capable of invasion and inhabitation even on live trees.

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The addition of maitake homogenate to white bread dough affected the gas production by baker's yeast. After 4 hours of incubation, total gas production increased about 2.1 times more than that of standard dough, and a few large holes and many small holes appeared on top of the dough containing maitake after 6 hours of incubation. Gas production increased with the increasing consumption of glucose and mannitol in maitake. The addition of maitake to wheat flour increased the production of low molecular weight sugar (fermentable sugar). Therefore, we concluded that the addition of maitake to white bread dough provided nutrients as a fermentable sugar for the yeast. This resulted in the excessive initial production of gas forming holes upon exiting the dough and reducing the volume of the dough as a result. Consequently, the dough in which holes were formed on top was broken before oven baking, and the loaf volume and specific loaf volumes of the bread containing 5% maitake was markedly decreased when an automatic bread baker was used.

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The mycelium of Coprinus phlyctodosporus accumulated mannitol during the vegetative growth period but more than half of the amount was decreased by translocation into the fruit-bodies during development. The mannitol content in the fruit-bodies increased during their development. The mycelium only contained NAD-MDH, but the fruit-bodies contained both NADP- and NAD-MDHs. NAD-MDH in mycelium continue to increase until the fruiting initiation, and then began to decrease thereafter. On the other hand, both NAD- and NADP-MDH activities in the fruit-bodies increased until the middle stage of development and then decreased with maturation. NAD-MDH reactions for the mannitol formation in both mycelium and fruit-bodies showed the optimum pH at 7.0, and its Km values for fructose and NADH were 6.0×10^<-2> M and 1.0×10^<-5>M, respectively. The mannitol oxidation by NAD-MDH showed the maximum activity at pH 8.8, and its Km values for mannitol and NAD were 2.8×10^<-3>M and 2.3×10^<-4>M, respectively. On the other hand, the Km values of NADP-MDH in fruit-bodies for fructose and NADPH at pH 7.0 were 3.3×10^<-1> and 1.4×10^<-5>M. Those for mannitol and NADP were 1.1×10^<-2>M and 1.0×10^<-4>M at the optimum pH of 9.6, respectively. These results suggest that mannitol was synthesized in the mycelium and translocated into the fruit-bodies, at which it was converted to fructose by NADP-MDH and then entered into the glycolytic pathway of this mushroom.

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