The active constituent in yeast extract for fruit body formation of Lentinula edodes

This investigation attempted to identify the active constituent in yeast extract for fruit body formation of Lentinula edodes. Yeast extract was applied to a Sephadex G-25 column and was divided into five fractions, I to V, on the basis of the peaks of UV absorption. Of the five fractions, fraction II was the most effective for fruit body formation. Fraction II was still effective for fruit body formation at a dilution of 10(-2), but its activity was drastically lowered by autoclaving under alkaline conditions. Thiamin, which is well known to exist in yeast extract and to be sensitive to alkaline hydrolysis, was contained in fraction II in a free form at about 85% of the total content. When most of the thiamin was eliminated by passing it through a permtid column or heating it under alkaline conditions, the fruiting activity of fraction II disappeared. The addition of thiamin, instead of fraction II, also caused fruit body formation in the basal peptone-glucose liquid media. Thus, it was concluded that thiamin must be the active substance in fraction II of the yeast extract for fruit body formation of L. edodes.