菌根形成食用担子菌, ホンシメジおよびマツタケの子実体形成研究の現状

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記事区分：原著[Author Abstract]The ectomycorrhizal fungi Tricholoma matsutake and Lyophyllum shimeji are famous and delicious edible mushrooms from Japan. Since they form mycorrhiza on the fine roots of living plants, their growth depends facultatively on living plants. To cultivate these fungi for in a pure culture, glucose and a few other monosaccharides must be used as carbon sources. In 1994,it was reported that L.shimeji can form mature fruit-bodies on a medium that consists mainly of barley grains ; in addition, they form without a host plant. These observations indicate that some mycorrhizal mushroom fungi have the ability to utilize barley starch. When fungi form fruit-bodies, large amounts of mycelia may be needed either to store nutrients or to transport nutrients to the fruit-bodies, or for both purposes. However, it is very difficult to cultivate large amounts of mycelia using monosaccharides in a pure culture. The addition of low molecular weight substances in high concentrations increases the osmotic pressures of a medium, which in this case would suppress the growth of the mycelium. Then, amylase productions during the vegetative mycelial growth of T.matsutake (No.114 and Z-1 strain), which hydrolize starch as a substrate for the growth of the fungi were examined using a somewhat modified matsutake liquid medium. Amylase activity (α-and gluco-amylase) in the culture filtrates had relatively high values at 40 days after the inoculation. Maximum activity was attained 80 days after inoculation. α-Amylase showed more activity than glucoamylase in both strains. Amylase activity in the culture filtrate of T.matsutake was assayed by using several kinds of starch as the substrate ; the starches were purified from barley (5 kinds), corn, sweet potato, and potato. The enzyme was most active in the presence of the starch prepared from the "Amagi" and "Ichibanboshi" strains in the "Nonwaxy" barley group among the starches. This activity was were observed at a circa 2.0-fold higher value than that of the control (potato). The addition of potato and yam to the culture medium increased the dry weight of mycelia 4.8-5.6 times, as compared to the control (without addition) ; moreover, the value of amylase activity was 1.9-2.6 times that of the control. A positive correlation between vegetative mycelial growth and amylase activity was detected. To elucidate the properties of extracellular amylases in the T.matsutake Z-1 strain, the amylase fractions obtained from the DEAE-Toyopearl column chromatography were identified. One type of α-amylase, glucoamylases and α-glucosidases showed activity upon analysis by thin layer chromatography using hydrolyzates.[JST抄録]菌根形成食用担子菌,ホンシメジ(Lyophyllum shimeji)およびマツタケ(Tricholoma matsutake)の子実体形成研究についてレビューした。最初に,菌根形成きのこ類の人工栽培が難しい理由の一端を説明した。次に,ホンシメジが人工栽培化に至った過程,また,マツタケの人工的な子実体形成研究の現状について,これらの菌根菌類の生育生理の面から成育基質として重要な澱粉の利用性に注目して,アミラーゼなどの生成酵素との関連で述べた。マツタケ「シロ」中にどの程度の澱粉が含まれ,マツタケ菌がアミラーゼを生成してその澱粉をどの程度利用しているかなど今後解明すべき点は多い。
2001-03-31

菌根形成食用担子菌, ホンシメジおよびマツタケの子実体形成研究の現状

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