We conducted food science and biochemical research on the functional ingredients contained in mushrooms, and obtained the following results. 1. Enzymes related to GABA production in <Flammulina velutipe<i>Grifora frondosa</i>, and <i>Lentinula edodes</i>, were purified and characterized. 2. The properties of the red chromoprotein of <i>Pleurotus salmoneostramineus</i> were clarified. 3. It was clarified that the yellow pigment contained in<i>P. salmoneostramineus</i> and <i>Pleurotus citrinopileatus</i> is a substance for water-soluble melanin. 4. The function of trehalose and syringic acid in edible mushrooms was clarified. 5. The method for preparing a high-amino acid fermented solution using of edible mushroom protease was established.

View full abstract

<i>Lentinula edodes</i> (shiitake) is a white-rot fungus that can break down plant cell wall carbohydrates including cellulose, hemicellulose, and pectin by glycoside hydrolases (GHs). Among these, degradation of pectin has been suggested to be important for the initial stages of wood decay. We purified and characterized a pectin-degrading enzyme from <i>L. edodes</i> (LePG28A) that has endotype polygalacturonase activity. The enzyme showed synergistic action with oxalic acid in the degradation of calcium polygalacturonate gel, indicating that oxalic acid has a role in the chelation of calcium ions from pectic substrates. The cell walls of fungi such as <i>L. edodes</i> are constructed mainly from chitin and β-1,3/1,6-glucans. Therefore, fungi also produce GHs associated with cell wall polysaccharides. Lentinan is aβ-1,3/1,6-glucan with physiological activities that are found in fresh <i>L. edodes</i> fruiting bodies. Lentinan content in mushrooms decreases rapidly during post-harvest storage due to the actions ofβ-1,3-glucanases. We developed a shiitake mushroom strain with high lentinan content through the downregulation ofβ-1,3-glucanase EXG2.

View full abstract

By next-generation sequencing analysis, 24 mating-type genes and mating-type-related genes were identified in the bipolar basidiomycete <i>Rhizopogon reseolus</i>, including two homeodomain protein genes, four pheromone receptor genes, and 18 genes around the A mating-type locus that are conserved among mushrooms.The 24 genes were clustered in three different nodes (assembled contig nucleotide sequences). Two pheromone receptor genes, Rcb1 and Rcb2, were closely linked with the Hox genes on node 8,230, and the distance between A2-Rcb1 and A2-hox2 was only 875 bp. The other two Rcb genes (A2-Rcb3 and A2-Rcb4) were located on node 11,781. Six genes that flanked the A mating-type locus and are conserved with other mushrooms were found in node 880. Linkage analysis using single-nucleotide polymorphism analysis revealed that the 24 genes located in the three nodes were genetically linked, and that the three nodes comprised a partial nucleotide sequence of a single chromosome. We hypothesized that the chromosome on which the A mating-type locus is located might have resulted from a recombination event between the A mating-type gene cluster and the pheromone and pheromone receptor cluster in ancient species of this bipolar mushroom.

View full abstract

Soluble dietary fiber was prepared from the hot water extract of the fruiting bodies of beefsteak fungus, <i>Fistulina hepatica</i> (Schäeff: Fr.) Fr., to evaluate its pharmaceutical properties. The fruiting bodies contained approximately 7% (dry weight) soluble dietary fiber of which the molecular mass was estimated to be 12.5 ± 0.8 kDa through high-performance liquid chromatography. In vitro glucose diffusion assays suggested that a 0.25% (w / v) solution of the soluble dietary fiber had significantly decreased glucose diffusion by up to 50% in an experimental vessel. Furthermore, the soluble dietary fiber exhibited high bile acid-binding capacity. These results suggest that ingestion of this soluble dietary fiber may prevent rapid increases in blood glucose and decreases serum cholesterol levels in humans.

View full abstract