Studies on structure and generation of volatile formating gene in edible mushrooms

1997 Fiscal Year Final Research Report Summary

• Project/Area Number: 07456154
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 食品科学・栄養科学
• Research Institution: Niigata university
• Principal Investigator: HAYAKAWA Toshiro Niigata University, Faculty of Agriculture, Professor, 農学部, 教授 (60018538)
• Co-Investigator(Kenkyū-buntansha): JOH Toshio Niigata University, Faculty of Agriculture, Assistant, 農学部, 助手 (00251794) ; MITSUI Toshiaki Niigata University, Graduate School of Science and Technology, Associate Profess, 大学院・自然科学研究科, 助教授 (70183960)
• Project Period (FY): 1995 – 1997
• Keywords: lipoxygenase / hydroperoxide lyase / lentinus edodes / grifola frondosa / pleurotus streatus / molecular weight of lipoxygenase / 1-octen-3-ol / induction

Research Abstract

Induction of lipoxygenase in mycelia of Shiitake mushroom (Lentinus edodes) was studied.
Fresh weight of mycelia cultured for 3 weaks in soybean medium, in which soybean oil and flour were respectively used as carbon and nitrogen sources, was 11-fold that in GC medium, in which goucose and casamino acids were respectively used as carbon and nitrogen sources. Mycelial forms of both cultures differed greatly : GCculture, a large spherical form ; soybean soybean culture, a small spherical form or a fibriform. Lipoxygenase activity of mycelia cultured in soybean medium was 26-fold higher than the corresponding activity in GC medium, indicating the induction of lipoxygenase in mycelia by soybean culture. Optimum concentrations of soybean oil and flour in the medium for the growth of mycelia and the induction of lipoxygenase were 60 ml/1 and 12g/1, respectively. Active staining of lipoxygenase revealed that among 4 lipoxygenase isozymes in mycelia of GC culture only one isozyme is induced by soybean culture. The induced lipoxygenase showed high activity below pH 4.5, and was stable at pH 3.0 to 8.5 and below 50ﾟC.The enzyme had a higher specificity against linoleic acid and arachidonic acid than against linolenic acid. Cu^<2+>, N-ethylmaleimide and indoactic acid inhibited the enzyme activity.
Analysis of Volatile compouds from Maitake mushroom (Grifola frondosa) homogenate was done by gaschromatograph equipped with PEG 20M fused silica capilary column (i.d.0.25 mm x 60 m).
The capacity of maitgake lipoxygenase and hydroperoxidelyase to generate short-chaine volatile carbonyl compounds depended on the concentrations of enzyme, substrate fatty acids, and duration of incubation period. The major volatile compounds generated from the oxidation of linoleic acid by lipoxygenase and hydroperoxide lyase in maitake homogenate were 1-octen-3-ol (60%), 3-octenol (31%), 2-octenal (3%), n-heptanal (2.2%), methyl cinnamate (1.5%), nerolidol (1.3%), 2-dcanone (0.8%), n-octanal (0.4%), 3-octen-3one, and etc.
The molecular weight of lipoxigenase from Hiratake mushroom (Pleurotuso streatus), was 87.00 by the use of gel chromatography with Sephacryl S-400.