Evaluation of the chemical qualities and microstructural changes of Lentinula edodes caused by airborne ultrasonic treatment combined with microwave vacuum drying.

This study analyzed a new drying method using airborne ultrasound combined with microwave vacuum to study its effect on the quality characteristics and microstructure of dehydrated L. edodes. Ultrasonic treatment resulted in many micropores in the product, forming the sponge effect caused by ultrasonic waves, which can promote the rapid evaporation of water in the product. Samples of Lentinula edodes individuals were dried using four methods: hot air drying (HAD), microwave vacuum drying (MVD), microwave vacuum drying after ultrasonic pretreatment (US+MVD) and airborne ultrasonic treatment combined with microwave vacuum drying (USMVD). The results showed that USMVD can reduced the loss of total sugar, total phenol, and total antioxidants in L. edodes, and increased the relative content of ergosterol, sulfur compounds, and free amino acids (p < 0.05). Scanning electron microscope observation revealed that USMVD resulted in a uniform reticular porous structure, which could better maintain desirable levels of nutrients. Therefore, USMVD can produce high quality products. PRACTICAL APPLICATION: Airborne ultrasonic waves combined with MVD provides an innovative drying method for mushrooms, which has not been studied at present. The mixed drying method has great potential in maintaining product quality. It provides a theoretical basis for studying drying technology in the future.

Cell wall structure of secreted laccase-silenced strain in Lentinula edodes.

Laccase1 (Lcc1) is abundantly secreted from vegetative mycelia into culture medium by Lentinula edodes. Down-regulation of lcc1 in L. edodes results in abnormal hyphal structure and thinner cell wall in mycelia. In this study, we observed the effects of Lcc1 on the hyphal morphology and cell wall structure of L. edodes. A thick cell wall and fibrous layer were clearly observed in the lcc1-silenced strain ivrL1#32, when purified Lcc1 (0.1 mU/mL) was added to the culture medium. The ratio of cell wall polysaccharide contents was compared between the ivrL1#32 strain and the wild-type (WT) strain SR-1, revealing that levels of the alkali soluble ß-1,3-1,6-glucan were significantly lower in the lcc1-silenced strain than in the WT strain. Chronological analysis revealed that chitin content in the cell wall did not increase over time, but that the alkali soluble ß-1,3-1,6-glucan content increased after Lcc1 secretion in the WT. Taken together, these data suggest that the increased level of ß-1,3-1,6-glucan induced by Lcc1 in the mycelial cell wall contributes to increased cell wall thickness and strength.

Brown Mycelial Mat as an Essential Morphological Structure of the Shiitake Medicinal Mushroom Lentinus edodes (Agaricomycetes).

We show here, to our knowledge for the first time, that the brown mycelial mat of the xylotrophic shiitake medicinal mushroom, Lentinus edodes, not only performs a protective function owing to significant changes in the ultrastructure (thickening of the cell wall, increased density, and pigmentation of the fungal hyphae) but also is a metabolically active stage in the development of the mushroom. The cells of this morphological structure exhibit repeated activation of expression of the genes lcc4, tir, exp1, chi, and exg1, coding for laccase, tyrosinase, a specific transcription factor, chitinase, and glucanase, which are required for fungal growth and morphogenesis. This study revealed the maximum activity of functionally important proteins with phenol oxidase and lectin activities, and the emergence of additional laccases, tyrosinases, and lectins, which are typical of only this stage of morphogenesis and have a regulatory function in the development and formation of fruiting bodies.

Alteration in the ultrastructural morphology of mycelial hyphae and the dynamics of transcriptional activity of lytic enzyme genes during basidiomycete morphogenesis.

The morphogenesis of macromycetes is a complex multilevel process resulting in a set of molecular-genetic, physiological-biochemical, and morphological-ultrastructural changes in the cells. When the xylotrophic basidiomycetes Lentinus edodes, Grifola frondosa, and Ganoderma lucidum were grown on wood waste as the substrate, the ultrastructural morphology of the mycelial hyphal cell walls differed considerably between mycelium and morphostructures. As the macromycetes passed from vegetative to generative development, the expression of the tyr1, tyr2, chi1, chi2, exg1, exg2, and exg3 genes was activated. These genes encode enzymes such as tyrosinase, chitinase, and glucanase, which play essential roles in cell wall growth and morphogenesis.

[Activity and expression of laccase, tyrosinase, glucanase, and chitinase genes during morphogenesis of Lentinus edodes].

Activation of expression of the lcc4 and tir genes encoding laccase and tyrosinase was observed during transition of a xylotrophic basidiomycete Lentinus edodes from the vegetative to the generative growth stages. This was especially pronounced in the brown mycelial mat (the stage preceding formation of the fruiting bodies). Development of this structure was shown to be associated with a sharp increase of laccase and tyrosinase activities, as well as with rearrangements in the phenol oxidase complex. Formation of the tissues with thickened cell walls was associated with enhanced expression of the chi and exg1 genes encoding chitinase and glucanase, respectively. Exogenous treatment of the vegetative mycelium with laccase preparation from the brown mycelial mat promoted formation of this morphological structure. Activation of the lcc4, tir, chi, and exg1 genes may be used as a marker of readiness to fruition in xylotrophic fungi.

Absorbed-dose estimation and quality attributes of gamma-irradiated fresh shiitake mushrooms.

BACKGROUND: The general use of food irradiation requires reliable identification methods as well as extensive quality characterization. Shiitake (Lentinus edodes) mushrooms, packed in polystyrene trays and covered with polyvinylchloride film, were investigated for dose-dependent identification and quality characterization upon gamma irradiation (0, 1, 2, and 3 kGy). RESULTS: Thermoluminescence (TL) analysis of separated minerals provided excellent results to characterize the irradiated mushrooms. Low-dose re-irradiation (200-600 Gy), medium-dose re-irradiation (1-3 kGy) and high-dose re-irradiation (2-6 kGy) were performed and compared using an additive dose method. An electronic-nose analysis showed a difference in the volatile profiles of mushrooms following irradiation. One-kGy-irradiated mushrooms showed similar or better quality attributes to those of the control samples. Scanning electron microscopy revealed the dose-dependent degradation in microstructure of mushrooms upon irradiation. CONCLUSION: An absorbed dosed estimation was possible using TL analysis in which 1-3 kGy re-irradiation technique gave most promising results. An E-nose analysis effectively distinguished the samples based on irradiation history. The best quality attributes were observed at 1 kGy irradiation. However, the drastic effects of irradiation were prominent in 2 and 3 kGy-irradiated mushrooms.

Reduction of organic and inorganic selenium compounds by the edible medicinal basidiomycete Lentinula edodes and the accumulation of elemental selenium nanoparticles in its mycelium.

We report for the first time that the medicinal basidiomycete Lentinula edodes can reduce selenium from inorganic sodium selenite (Se(IV)) and the organoselenium compound 1,5-diphenyl-3-selenopentanedione-1,5 (DAPS-25) to the elemental state, forming spherical nanoparticles. Submerged cultivation of the fungus with sodium selenite or with DAPS-25 produced an intense red coloration of L. edodes mycelial hyphae, indicating accumulation of elemental selenium (Se(0)) in a red modification. Several methods, including transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS), and X-ray fluorescence, were used to show that red Se(0) accumulated intracellularly in the fungal hyphae as electron-dense nanoparticles with a diameter of 180.51±16.82 nm. Under designated cultivation conditions, shiitake did not reduce selenium from sodium selenate (Se(VI)).

Identification and characterization of gamma-irradiated dried Lentinus edodes using ESR, SEM, and FTIR analyses.

UNLABELLED: A detailed electron spin resonance (ESR) analysis for different parts of gamma-irradiated (0 to 50 kGy) dried mushroom (Lentinus edodes) was conducted to identify radiation-induced signals. All studied mushroom parts except gills produced strong dose-dependent radiation-induced ESR signals particularly at about g = 2.0076, 20005, and 1.9911 demonstrating the generation of crystalline sugar radicals following irradiation. The intensity of these signals was highest in cap skin samples, followed by the cap core, stem skin, whole mushroom powder, and stem core samples, respectively. ESR-based identification was easily possible at 2 kGy or more using mushroom cap skin or cap core as samples. The radiation-induced ESR signals were found sensitive to thermal treatment showing the limitation of ESR-based detection in case of heat-processed samples. Scanning electron microscopy (SEM) showed micro-structural damage upon irradiation resulting decreased percentage of rehydration; however, no major alteration was observed through the Fourier transform infrared (FTIR) spectra. Irradiation changed the structural morphology; however, the main functional groups were stable against radiation treatment. PRACTICAL APPLICATION: Food irradiation can confirm hygienic quality and prolong the product shelf life. However, due to lack of international consensus, effective identification methods and detailed quality characterization are required for the general use of this technology.

Structure and composition changes in the cell wall in relation to texture of shiitake mushrooms (Lentinula edodes) stored in modified atmosphere packaging.

BACKGROUND: Firmness in shiitake mushroom (Lentinula edodes) is an important textural attribute affecting consumer attitudes toward freshness and quality. In this study, the effects of modified atmosphere packaging (MAP) treatments on structure and composition changes in cell walls in relation to the texture of mushrooms were investigated. RESULTS: Shiitake mushrooms were packaged in low density polyethylene bags with no holes (M(0)), two microholes (M(1)), four macroholes (M(2)), stored at 4 degrees C for 16 days with non-wrapped mushrooms as control. Control mushrooms showed the highest firmness value due to significant increase of cellulose and chitin. All three MAP treatments reduced losses of protein and polysaccharides; the M(2) treatment can best preserve the original texture while mushrooms in M(0) became soft and deteriorated, possibly due to higher CO(2) accumulation, lower cellulose and chitin content. Transmission electron microscopy performed on caps at harvest and after 16 days indicated that disintegration of plasmalemma had been alleviated by M(2) treatment, leading to better preservation of the cell wall. CONCLUSION: Our results suggest that differences in firmness of shiitake mushrooms during storage may be due to differences in cellulose and chitin concentrations. M(2) treatment may be a useful way of maintaining shiitake mushrooms texture during storage at 4 degrees C.

Generation of nuclear hybrids overcoming the natural barrier of incompatibility: transfer of nuclei from Lentinula edodes into protoplasts of Coriolus versicolor.

Heterokaryotic nuclear hybrids overcoming the natural barriers of incompatibility have been studied in basidiomycetes. To produce these nuclear hybrids between incompatible mushrooms, which have several potent pharmacological effects, nuclear transfer was performed between Lentinula edodes and Coriolus versicolor. Nuclei from serine auxotrophs of Lentinula edodes, LE207 (Ser-) were transferred into the protoplasts of arginine auxotrophs of Coriolus versicolor, CV17 (Arg-), using 30% polyethylene glycol 4000 in 10 mM CaCl2-glycine solution (pH 8.0). Nuclear transfer progenies were selected by nutritional complementation on minimal media supplemented with 0.6 M sucrose. The progenies were classified based on colony morphology to L. edodes-like, C. versicolor-like and non-parental type. Most of the progenies grew slower than either parent. The number of nuclei per cell was similar but the DNA content varied between progenies. The isozyme patterns of nuclear hybrids resembled either of the parent profiles or showed a mixed profile.