Fatty acid profiles of polar and non-polar lipids of Pleurotus ostreatus and P. cornucopiae var. ‘citrino-pileatus’ grown at different temperatures

The application of fatty acid (FA) composition data has now extended to studies of physiology, chemotaxonomy, and intrageneric differentiation, as well as to studies of human nutrition. Environmental factors such as nutritional components, oxygen, and temperature are known to affect lipid content and composition in living organisms, including fungi. In the present study, the polar and non-polar lipid content of Pleurotus ostreatus and P. cornucopiae var. citrino-pileatus fruiting bodies produced at temperatures ranging from 12–27 °C and from 17–27 °C, respectively, were analysed to evaluate the effect of temperature on lipid composition in these mushrooms. Results showed that lowering the growth temperature below 17 °C generally provided an expected increase in FA unsaturation in polar and non-polar lipids of P. ostreatus. Although raising the temperature above 17 °C did not show any clear-cut tendency in FA unsaturation, it did reveal that growth temperature had a differential effect on the FA profiles in fruiting bodies of P. ostreatus and P. cornucopiae. This study suggests that care should be taken when using FA content and unsaturation data for physiological, chemotaxonomic, and intrageneric differentiation studies, and that it may be possible to manipulate lipid unsaturation in Pleurotus spp. through modified growth temperatures.     

Effects of concentrated carbon dioxide on the fruiting of several cultivated basidiomycetes (II)

Edible basidiomycetesFlammulia velutipes andPleurotus ostreatus were cultivated in the usual manner on media based on sawdust and rice bran, and the cultures were exposed to slowly flowing CO₂-enriched air (550 (control), 3,000, 6,000, and 9,000µl/l) for seven days at different stages of cultivation. When the cultures were exposed at the primordium stage (less than 10 mm in length), length and yield of fruit-bodies increased and pileus expansion was slightly inhibited inF. velutipes, while inP. ostreatus length increased, yield decreased, and pileus expansion was greatly inhibited. When the cultures with fruit-bodies larger than 10 mm were exposed, length and yield were insensitive and pileus expansion was greatly inhibited inF. velutipes, while inP. ostreatus length was insensitive, but pileus expansion was heavily damaged by trumpet-like deformation and yield decreased. The different action of CO₂ on the two species appeared to be due to the different anatomical structures of their fruit-bodies.     

Effects of different heat pre-treatments of wheat straw on its microbial activity and colonization by different tropical and sub-tropical edible mushrooms

Quantitative differentiation of microbial activity in wheat straw substrate is described after different heat pre-treatments and addition of water during solid-state fermentation. All the 28 tested strains of tropical and sub-tropical edible mushrooms colonized sterile wheat straw. Substrate pre-treated at 25°C was primarily colonized by Coprinus sp. and other competitive microorganisms, and had the highest pH values. With some exceptions, increasing rates of growth occurred with substrate pre-treatment at 60 and 90°C. Best growth and highest speed of colonization were on sterilized straw. Heat pre-treatment of cereal straw at 60 and 90°C should be sufficient for commercial cultivation processes. Thus, a short fermentative pre-treatment could reduce the risk of infection. The strains tested do not differ significantly from those of temperate climates.R. Maziero was with the Instituto de Botânica, CP 4005, 01061-970, São Paulo, SP, Brazil, and is now at DISTAM Section of Industrial Microbiology, University of Milano, Via G. Celoria 2, 20133, Milano, Italy. F. Zadrazil is with the Institut für Bodenbiologie, Bundesforchungsanstalt für Landwirtschaft, Bundesallee 50, D 38116 Braunschweig, Germany.     

Rapid strain classification and taxa delimitation within the edible mushroom genus Pleurotus through the use of diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy

Fourier transform infrared (FT-IR) spectroscopy has been successfully applied for the identification of bacteria and yeasts, but only to a limited extent for discriminating specific groups of filamentous fungi. In the frame of this study, 73 strains - from different associated hosts/substrates and geographic regions - representing 16 taxa of the edible mushroom genus Pleurotus (Basidiomycota, Agaricales) were examined through the use of diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. A binary matrix, elaborated on the basis of presence/absence of specific absorbance peaks combined with cluster analysis, demonstrated that the spectral region 1800-600 cm(-1) permitted clear delimitation of individual strains into Pleurotus species. In addition, closely related species (e.g., Pleurotus ostreatus and Pleurotus pulmonarius) or taxa of the subgenus Coremiopleurotus demonstrated high similarity in their absorbance patterns, whereas genetically distinct entities such as Pleurotus dryinus, Pleurotus djamor, and Pleurotus eryngii provided spectra with noteworthy differences. When specific regions (1800-1700, 1360-1285, 1125-1068, and 950-650 cm(-1)) were evaluated in respect to the absorbance values demonstrated by individual strains, it was evidenced that this methodology could be eventually exploited for the identification of unknown Pleurotus specimens with a stepwise process and with the aid of a dichotomous key developed for this purpose. Moreover, it was shown that the nature of original fungal material examined (mycelium, basidiomata, and basidiospores) had an effect on the outcome of such analyses, and so did the use of different mycelium growth substrates. In conclusion, application of FT-IR spectroscopy provided a fast, reliable, and cost-efficient solution for the classification of pure cultures from closely related mushroom species.     

Cultivation of oyster mushrooms (<Emphasis Type="Italic">Pleurotus</Emphasis> spp.) on various lignocellulosic wastes

Cultivation of speciality mushrooms on lignocellulosic wastes represents one of the most economically and cost-effective organic recycling processes. Three species of Pleurotus, namely P. columbinus, P. sajor-caju and P. ostreatus were experimentally evaluated on untreated organic wastes including chopped office papers, cardboard, sawdust and plant fibres. Production studies were carried out in polyethylene bags of about 1 kg wet weight with 5% spawning rates of substrate fresh weight in a custom-made growth room especially designed for spawn run and cropping. The conversion percentage from dry substrate weight to fresh mushroom weight (biological efficiency) was determined. The highest biological efficiency was noted with P. columbinuson cardboard (134.5%) and paper (100.8%), whereas P. ostreatus produced maximum yield on cardboard (117.5%) followed by paper (112.4%). The overall yield of P. sajor-cajuwas comparatively low (range 47–78.4%). The average number of sporophore flushings ranged between 5 and 6 times. The findings that P. columbinus and P. ostreatus are superior to P. sajor-caju are consistent with previous reports elsewhere. Further evaluation of P. columbinus alone on different bagging systems containing partially pasteurized office papers as a growing substrate revealed that polyethylene bags resulted in 109.4% biological efficiency in contrast to pottery (86%), plastic trays (72%) or polyester net (56%). The above findings reveal an opportunity for commercial implication of oyster mushroom especially P. columbinus for utilization of different feasible and cheap recyclable residues.     

Differential Patterns of Constitutive Intracellular Laccases of the Vegetative Phase of Pleurotus Species

The constitutive intracellular laccase activity of ten strains of Pleurotus spp. was determined in vitro and by zymograms, using different substrates. Differences in the in vitro activities were observed between all the strains; however, zymogram patterns were only similar for strains within same species, independently of any of the three substrate (2,6-dimethoxyphenol, p-anisidine or o-tolidine) used. The differences observed in the number and positions of the isoforms in the gel suggest that laccase zymograms can be used to differentiate species of this organism.     

Can mushrooms fix atmospheric nitrogen?

It is generally reported that fungi likePleurotus spp. can fix nitrogen (N₂). The way they do it is still not clear. The present study hypothesized that only associations of fungi and diazotrophs can fix N₂. This was testedin vitro. Pleurotus ostreatus was inoculated with a bradyrhizobial strain nodulating soybean andP. ostreatus with no inoculation was maintained as a control. At maximum mycelial colonization by the bradyrhizobial strain and biofilm formation, the cultures were subjected to acetylene reduction assay (ARA). Another set of the cultures was evaluated for growth and nitrogen accumulation. Nitrogenase activity was present in the biofilm, but not when the fungus or the bradyrhizobial strain was alone. A significant reduction in mycelial dry weight and a significant increase in nitrogen concentration were observed in the inoculated cultures compared to the controls. The mycelial weight reduction could be attributed to C transfer from the fungus to the bradyrhizobial strain, because of high C cost of biological N₂ fixation. This needs further investigations using¹⁴C isotopic tracers. It is clear from the present study that mushrooms alone cannot fix atmospheric N₂. But when they are in association with diazotrophs, nitrogenase activity is detected because of the diazotrophic N₂ fixation. It is not the fungus that fixes N₂ as reported earlier. Effective N₂ fixing systems, such as the present one, may be used to increase protein content of mushrooms. Our study has implications for future identification of as yet unidentified N₂ systems occurring in the environment.     

Enzyme activities and substrate degradation during white rot fungi growth on sugar-cane straw in a solid state fermentation

Two strains of Pleurotus spp., grown in solid state fermentation on sugar-cane straw, degraded the dry matter by 50% after 60 days. The rate of substrate consumption and the dry weight of fruiting bodies decreased in consecutive flushings. Both strains vigorously attacked hemicellulose (80% of total degradation) and lignin (70%). Fruiting bodies were rich in protein and lipids, and had a low content of carbohydrates and ash.     

Spawn viability in edible mushrooms after freezing in liquid nitrogen without a cryoprotectant

Five strains of edible mushrooms (Lentinula boryana, Lentinula edodes, Pleurotus djamor, Pleurotus pulmonarius, and Volvariella volvacea) were studied. Spawn were prepared from sorghum seeds and then incubated for 14 days under optimum conditions for each species. Once covered by mycelia, the sorghum seeds were placed in polycarbonate vials for freezing in liquid nitrogen. The effect of adding a cryoprotective solution before freezing (either 10% glycerol v/v or 5% dimethylsulfoxide v/v) was evaluated as a function of mycelial growth and percent viability. Three main treatments were undertaken: (1) freezing with a glycerol or dimethylsulfoxide cryoprotectant, (2) freezing with water and (3) freezing without cryoprotectant or water. Samples were maintained frozen for a week, after which time they were thawed (10 min at 30 degrees C) and the seeds placed in Petri dishes with a culture medium. A recovery rate of 96.8% was obtained for the total number of samples summed over all strains and treatments. In contrast, 99.2% of the samples frozen without cryoprotectant were recovered. The recovery of frozen mycelia was delayed with respect to a control group, which was not frozen. However, no difference was observed in percent recovery and mycelial diameter when a new series of spawn was prepared from mycelia that had been previously frozen. Results obtained from this experiment demonstrate that an adequate recovery of mycelia can be obtained without using a cryoprotectant. This capacity might enable large quantities of commercial mushroom strains to be handled at reduced production costs. It is suggested that the mycelia survived freezing without cryoprotectants because they were embedded and protected within the sorghum seeds used to elaborate the spawn.     

大叶桃花心木树皮化学成分研究

为了解大叶桃花心木(Swietenia macrophylla)树皮的化学成分,采用硅胶、凝胶、制备液相等手段分离、纯化,从其树皮提取物中分离得到9个化合物。根据理化性质及波谱数据,鉴定化合物结构分别为香草酸(1)、东莨菪素(2)、大黄素甲醚(3)、3,4,5-三甲氧基苯基-β-D-吡喃葡萄糖苷(4)、(+)-儿茶素(5)、5′-甲氧基异落叶松脂素-9′-O-β-D-吡喃木糖苷(6)、南烛木树脂酚-9′-O-β-D-吡喃木糖苷(7)、豆甾醇(8)、豆甾醇-3-O-β-D-吡喃葡萄糖苷(9)。除化合物5外,其余化合物为首次从该植物中分离。细胞毒活性试验表明化合物均无显著的细胞毒活性。     

Protein enrichment and digestibility of soft rush (<Emphasis Type="Italic">Juncus effusus</Emphasis>) and rice residues using edible mushrooms <Emphasis Type="Italic">Pleurotus ostreatus</Emphasis> and <Emphasis Type="Italic">Pleurotus sajor-caju</Emphasis>

Pleurotus species are found to be among the most efficient lignocellulolytic types of white-rot fungi. Rice is the main grain cultivated in the extreme south of Brazil. Defatted rice bran and straw are by-products of low aggregate value. Soft rush (Juncus effusus) is a common native plant also very abundant in the region. In the present work, we evaluated changes in substrate composition after growth of two white-rot fungal species: Pleurotus ostreatus and Pleurotus sajor-caju, aiming to increase protein content and digestibility from substrates through solid fermentations and obtain edible mushrooms of high aggregate value. For that, defatted rice bran, defatted rice straw and soft rush were utilized as substrate. The influence of the variables thermal treatment temperature of substrate, substrate moisture and concentration were evaluated on the protein content, digestibility and biological efficiency. The highest protein enrichment of rice bran in P. sajor-caju-fermented medium was due the fact that there was no fructification in these media, while for the P. ostreatus-fermented medium, part of the synthesized protein was converted into mushrooms. The highest protein enrichments were verified in medium with 80% moisture and 25% soft rush (47.1% using P. ostreatus and 49.0% using P. sajor-caju). A higher digestible protein increase was obtained for both species in media with 70% moisture and 25% soft rush.     

Changes in lignocellulolytic enzyme activites in six <Emphasis Type="Italic">Pleurotus</Emphasis> spp. strains cultivated on coffee pulp in confrontation with <Emphasis Type="Italic">Trichoderma</Emphasis> spp.

Summary The antagonistic effect of six Pleurotus spp. strains was studied in confrontation with three strains of Trichoderma spp. Pleurotus strains were cultivated on sterile coffee pulp, with and without a Trichoderma inoculant. Laccase, Mn peroxidase and endoglucanase activities were determined during incubation. Laccase production was also studied by PAGE analysis to detect enzymatic isoforms. Results show that the presence of Trichoderma induced a significant increase in oxidase production by the Pleurotus strains. Nevertheless, Trichoderma was not observed to induce laccase isoforms.     

Decolourization of Municipal Effluent and Sludge by Pleurotus sajor-caju and Pleurotus ostreatus

Summary The Americana Municipal Treatment Station, S?o Paulo, Brazil, manages 400 l of effluent s⁻¹, from domestic and textile origin, which produces an average of 20 t of sludge per day. The decolourization of the effluent and sludge by three strains of Pleurotus (Pleurotus sajor-caju F2, F6 and Pleurotus ostreatus) was evaluated. The strains of P. sajor-caju F2 and F6 were able to decolourize the sludge, while P. ostreatus was less efficient. Detoxification was appraised with three bioassays comprising the cnidarian Hydra attenuata, the alga Selenastrum capricornutum and lettuce seeds. After exposure to fungi, effluent toxicity decreased but not that of its sludge. Strain P. sajor-caju F6 presented signs of toxicity shown by electron microscopy in the presence of the effluent. The three strains produced high amounts of manganese-peroxidase (Mn–P) and laccase in the presence of the sludge. Although P. ostreatus produced large amount of Mn–P and laccase enzymes, these enzymes did not result in decolourization of the sludge, suggesting that other factors are likely to be involved. Carbon content decreased only in the treatment with P. ostreatus.     

The white-line-in-agar test is not specific for the two cultivated mushroom associated pseudomonads, Pseudomonas tolaasii and Pseudomonas "reactans"

A sharply defined white line in vitro forms between the pathogenic form of Pseudomonas tolaasii and another Pseudomonas bacterium, referred to as "reactans". This interaction has been considered as highly specific. However, results presented in this study rise doubt about the strict specificity of this interaction, as some other pseudomonads, associated with the cultivated mushroom Agaricus bisporus, also yielded a white line precipitate when they were streaked towards Pseudomonas tolaasii LMG 2342T. Moreover, some Finnish isolates inducing brown blotch symptoms on mushrooms like P. tolaasii(T), produced a typical white precipitate when streaked towards P. "reactans" LMG5329, even though phenotypical and genotypical features exclude these isolates from the species P. tolaasii. We propose that the white-line-in-agar (WLA) test should no longer be considered as an unequivocal diagnostic trait of P. tolaasii.     

Growth and laccase production by Pleurotus ostreatus in submerged and solid-state fermentation

Pleurotus ostreatus showed atypical laccase production in submerged vs. solid-state fermentation. Cultures grown in submerged fermentation produced laccase at 13,000 U l⁻¹, with a biomass production of 5.6 g l⁻¹ and four laccase isoforms. However, cultures grown in solid-state fermentation had a much lower laccase activity of 2,430 U l⁻¹, biomass production of 4.5 g l⁻¹, and three laccase isoforms. These results show that P. ostreatus performs much better in submerged fermentation than in solid-state fermentation. This is the first report that shows such atypical behavior in the production of extracellular laccases by fungi.