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[Introduction] Larix kaempferi (Larch), rich biomass in Hokkaido, is available as an inexpensive medium for mushroom production. We have previously developed a variety of Hypsizygus marmoreus with high ability to utilize larch sawdust without watering, Hm 219 (Marbure 219) with high fruit-body yield and high score of sensory evaluation, was selected. In this study, we investigated the effects of supplements to larch sawdust-based medium on taste components of fruit-bodies of Hm 219. [Materials and methods] The strain of H. marmoreus used in this study was Hm 219, the stock culture of Hokkaido Research Organization Forest Products Research Institute. Each 850 ml plastic bottle containing 540 g of larch sawdust-based substrate, was used for cultivation. Moisture content of each medium was adjusted to 61% based on the fresh weight of the mixture of solid materials. The substrate substituted with 0-40% of supplements (wheat bran, soybean curd residue and soybean shell) for rice bran as a nutrient, were used for cultivation. Cultivation was conducted by the standard procedure reported earlier (Harada et al., 2004). The harvested fruit-bodies were freeze-dried to determine the chemical composition. Soluble sugars, free amino acids and 5’-nucleotides were extracted with hot water from freeze-dried powder. These soluble components were determined by using HPLC. [Results] As a result, fruit-body yields on the substrate substituted with 20% of soybean shell for rice bran as a nutrient, were about 20% higher than those on the substrate with rice bran only. According to the replacement rate of soybean curd residue increasing , morphological quality of fruit-body tended to decline. As major free amino acids in fruit-body, monosodium glutamate-like (MSG-like) components which gave the umami taste, including aspartic acid and glutamic acid, and sweet components including alanine, threonine and serine were detected. As flavor 5’-nucleotides, GMP and IMP were found. In fruit-body of H. marmoreus, with respect to major soluble sugars, mannitol and trehalose were mainly contained. Each taste component content indicated differences among the different supplements to larch sawdust-based medium. The equivalent umami concentration (EUC ) is the concentration of MSG equivalent to the umami intensity of that given by the mixture of MSG and the 5’-nucleotide (Lee, Yu-Ling et al., 2009). The EUC value in a cultivation condition was more 15% higher than that of control condition. [References] Harada, A. et al. (2004) Effects of strain and cultivation medium on the chemical composition of the taste components in fruit-body of Hypsizygus marmoreus. Food Chemistry, 84, 265-270. Lee, Yu-Ling et al. (2009) Composition and non-volatile components of Hypsizygus marmoreus, LWT- Food Science and Technology, 42, 594-598.