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BISSETT, J., 1991c. A revision of the genus Trichoderma IV. Additional notes on section Longibrachiatum. Can. J. Bot. 69 . 2418-2420. A revision of the genus Trichoderma IV. Additional notes on section Longibrachiatum
The abundance and diversity of indigenous Trichoderma fungi were tested for correlations with the natural colonization of symbiotic arbuscular mycorrhizal fungi (AMF) in Cd-, Zn- and Ni-polluted soils. Infection frequency (F%) and arbusculum richness (a%) of the mycorrhiza fungi were estimated on red clover grown in a pot experiment set up with calcareous loamy chernozem soil contaminated with Cd, Ni and Zn salts (in 0, 30, 90 and 270 mg kg -1 dry soil concentration) in the field, eight years prior to the pot experiment. Correlation analyses were used to assess the effect of different heavy metal loads on the interrelations of these two types of beneficial fungi. When the test was performed for single variables, significant correlations could be found with very close (r > 0.96 at p < 0.05) results. The rate and direction (positive or negative) of correlations, however, varied with the type of heavy metals. With the combinations of some Trichoderma and mycorrhiza parameters a significant model was obtained for the infection frequency (R² = 0.9405 at p = 0.0062) and for arbusculum richness (R² = 0.997 at p = 0.0007), which suggests a significant complex influence between the symbiotic (AMF) and the free-living ( Trichoderma ) beneficial fungi. This interaction was altered by heavy metals. In the Ni treatments, the correlation data were always negative between the two groups of beneficial fungi.
Because of the need for renewable energy resources, cellulose, which can be enzymatically hydrolyzed to glucose, has drawn lot of attention during the past decade. However, the process of cellulose conversion using cellulase is not yet economically feasible because of the high cost of enzymes. Factors influencing the cellulase production of Trichoderma koningii using both acid and steam treated sugar cane bagasse and rice straw as carbon sources were investigated. The highest levels of cellulase activities were obtained using a culture medium containing urea and (NH4)2SO4 together as nitrogen sources at 0.217% and 0.241% for both carbon sources. When the culture medium was supplemented either with 0.5% Tween 60 or Tween 80, the rate of cellulase production was increased considerably. Maximum levels of both filter paper and CMC-ase activities produced on both media were obtained at 25 °C and 100 r.p.m., while the highest level of â -glucosidase production was obtained at 30 °C and 200 r.p.m.
Aquatic weed water hyacinth was evaluated for its potential to be used as feedstock for fermentable sugar production via enzymatic hydrolysis. Critical factors (pretreatment of substrate, concentration of substrate, incubation period, pH, incubation temperature) affecting enzymatic hydrolysis of water hyacinth were optimised for maximum production of fermentable sugars. Enzyme (mainly cellulase) produced by Trichoderma reesei ATCC 26921 in a simple medium containing the plant biomass as the sole carbon source was directly used at a particular concentration for hydrolysis. It was observed that acid-alkali pretreated water hyacinth was far more accessible to cellulolytic enzymes than untreated one and hence was hydrolyzed to a greater extent. Maximum hydrolysis (41.7%) was obtained with 4% (w/v) pretreated water hyacinth after 72 h of incubation at pH 5.2 and at a temperature of 45 °C. With a view to enhance the percentage of enzymatic hydrolysis, culture metabolite (enzyme source) of T. reesei was supplemented with enzyme from a β-glucosidase mutant, Aspergillus phoenicis . This β-glucosidase enriched cellulase preparation facilitated further enhancement (49.7%) of hydrolysis at FPase to β-glucosidase ratio of 1:1.2. Gas-liquid-chromatographic analysis of the hydrolyzed broth, thus obtained under optimal conditions, revealed the presence of glucose (12.5 g l −1 ) as the most predominant fermentable sugar besides having the presence of xylose, arabinose, mannose and galactose. This widens up the feasibility of utilising such hydrolysate as a cheap carbon source (glucose and to some extent xylose) for yeast fermentation to produce fuel ethanol.
Cadmium, nickel or zinc contaminated soils originating from a long-term heavy metal field experiment were used to assess the influence of those particular treatments on the coexistence of various Trichoderma species. The abundance of six indigenous Trichoderma spp. - T . atroviride , T . harzianum , T . pubescens , T . tomentosum , T . virens and T . viride - were studied 12 years after the application of Cd, Zn and Ni salts on four levels (0, 30, 90 and 270 mg·kg -1 ) in a calcareous chernozem soil. Trichoderma fungal colonies from the soil particles were estimated on selective media. The isolated strains were taxonomically characterized by microscopic visualization. A reduced Trichoderma fungal colonization was found at the lower ratio of the studied metals. No colonization could be recorded in the case of Cd, and a slightly increased abundance at Ni and Zn metal salts at the highest 270 mg·kg -1 doses. The species composition of the fungi varied considerably in the contaminated samples as a function of the metals and the applied doses. Correlation analysis revealed that the population density of T . atroviride , T . harzianum , T . pubescens , T . viride was negatively affected by the available Cd concentration. The nickel content of the soil, however, correlated positively with the abundance of T . harzianum (r = 0.955) and T . virens (r = 0.964). In addition to this finding, the frequency of T . viride and T . tomentosum showed significant positive and negative correlation with the Zn treatment (r = 0.955; r = -0.965, respectively). Great differences between the correlation and partial correlation coefficients suggested that the heavy metals may alter not only the abundance of the fungi, but the interspecific relationships among the indigenous Trichoderma population, as well. This fact is considered to have further influence on some other biotic parameters and the soil functioning in heavy-metal-affected soils.
. Z. Naár B. Biró 2006 Species composition of indigenous Trichoderma fungi affected by Cd, Ni and Zn heavy metals in calcareous chernozem soil
In the microflora of sunflower seeds stored in domestic stores the, Alternaria species dominate, while those of Penicillium, Trichoderma, Stemphylium and Absidia spp. are present in lower numbers. During model tests (cca 20% seed moisture content, 25 °C, 4 weeks storage) the Alternaria species were almost completely eliminated and on the seeds mainly Aspergillus species, characteristic of stores, propagated. The moulds significantly deteriorated the quality of the seed and that of the produced oil and meal (reproductive ability, germinating power, oil content, lipoxygenase enzyme activity, acid value, peroxide value, fatty acid composition, UV absorbance, colour, sensorial properties, as well as the protein content, amino acid composition, colour and the smell of the meal), but no aflatoxin production occurred. The findings offer a comprehensive picture on the multiple destructive effects of incorrect storage.
The effect of a pure endoxylanase (Xyn2) and endoglucanase (EgII) from Trichoderma reesei on bread flour quality were compared to a commercial endoxylanase from Aspergillus niger (Com-xyl) and a cellulase-xylanase cocktail from T. reesei (Cel-xyl). Effects of these enzymes on dough quality, bread weight, height and crumb softness were analysed. Results obtained during commercial-scale baking tests often differed from those obtained during laboratory-scale tests; indicating that results from laboratory-scale baking tests cannot be extrapolated to commercialscale bread production. Low levels of endoxylanase activity benefited bread height and volume without affecting slice brightness in commercial-scale tests. The addition of endoglucanases and α-amylases can also be advantageous resulting in less endoxylanase activity required to obtain similar results.
In the process of making ethanol from lignocellulosics, enzyme production is still the most crucial and costly step. Trichoderma reesei Rut C-30 is the best known cellulase producer. This fungus is very good in endo- and exoglucanase production, however, the amount of β-glucosidase excreted is not sufficient for hydrolysis. In addition, T. reesei Rut C-30 is sensitive to inhibitors generated during steam-pretreatment of wood. In the present study, two good cellulase producers were selected from 16 fungal strains and investigated regarding filter paper activity (FPU) and β-glucosidase activity using inexpensive lignocellulosic carbon sources for cultivation. T. reesei Rut C-30 proved to be a good cellulase producer, resulting in a maximum FPU of 1.39 FPU ml &1 on washed, steam-pretreated willow, but the β-glucosidase activity was insufficient. High β-glucosidase activities were reached with T. viride OKI B1 on all substrates, with a maximum activity of 1.62 IU ml &1 on steam-pretreated spruce.
Mycoviruses are known to infect fungi of different habitats and life style. Some of them, like the Mushroom Virus X (MVX) complex, cause abnormal development of fruiting bodies and severe yield losses in mushroom cultivation. Most mycoviruses have a double-stranded RNA (dsRNA) genome, therefore dsRNA-detection is frequently used as a first step to identify virus infection. In relation with MVX 23 dsRNAs species have been described, occurring in variable number and combination in diseased mushrooms. The aim of our experiments was to find out whether dsRNA-immunoblotting can be used to detect dsRNA in small samples of cultivated A. bisporus varieties and of wild growing Agaricus species. We found that by immunoblotting, the same dsRNA species were detected in apparently healthy cultivated champignon fruiting bodies and in MVX-infected reference samples, respectively, as by conventional CF11 chromatography, but for immunoblotting a much smaller sample size was needed. In two out of three deformed fruit bodies of cultivated A. bisporus from Hungary we detected a 4.1 kbp dsRNA species which was also present in the MVX infected reference samples. Diverse and variable dsRNA patterns were observed in apparently healthy samples of 12 wild growing Agaricus species, indicating that extreme care should be taken when non-cultivated Agaricus is used for breeding new varieties. Non-sterile cultures and environmental mushroom specimens are fairly often mixed with parasitic and endofungal organisms, therefore, we also tested fungi isolated from mushroom cultures. Here again, 1–7 dsRNA species were found in extracts of Trichoderma and Dactylium isolates and of Mycogone-infected sporophores. Our results demonstrate clearly that dsRNAs from very different origins can be present in cultivated champignon and support the view that the MVX symptom-associated dsRNAs are probably of polyphyletic origin and do not represent one defined virus.
