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C R Wilson - One of the best experts on this subject based on the ideXlab platform.
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effect of inoculum density of sclerotium cepivorum on the ability of Trichoderma koningii to suppress white rot of onion
Plant Disease, 2004Co-Authors: D A Metcalf, J J C Dennis, C R WilsonAbstract:ABSTRACT Amendment of soil with Trichoderma koningii strain Tr5 grown on autoclaved white millet grain provided between 63 and 79% control of white rot of onion when added to soil containing 10, 25, 50, or 100 sclerotia of Sclerotium cepivorum per kilogram of soil at the time of onion seed sowing. There was no significant difference in the proportion of S. cepivorum infections suppressed among the different sclerotial density treatments. Rhizosphere colonization by T. koningii Tr5 was assessed by incubating onion roots sampled from plants growing in soil with the appropriate density of sclerotia, on a Trichoderma selective medium (Rose bengall-Allisan-streptomycin-Previcur agar) developed for the purpose of the study. Trichoderma spp. isolated were typed by comparison of culture morphology as well as polygalacturonase (PG) (EC 3.2.1.15) and pectinesterase (PE) (EC 3.1.1.11) isozyme profiles to the series of one PG and two PE isozymes known to be produced by T. koningii Tr5. The method was used successfull...
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the process of antagonism of sclerotium cepivorum in white rot affected onion roots by Trichoderma koningii
Plant Pathology, 2001Co-Authors: D A Metcalf, C R WilsonAbstract:Trichoderma koningii (strain Tr5) grew in the epidermal mucilage of onion roots without entering healthy epidermal tissue. When placed on the epidermis of Sclerotium cepivorum-infected roots, T. koningii colonized epidermal passage cells, with little colonization of other epidermal tissues, then branched and spread throughout the root cortical tissues damaged by enzymes and toxins which diffused ahead of S. cepivorum hyphae, and impeded the path of the infection. When T. koningii colonized infected tissue, many S. cepivorum hyphae became detached at septa, cell walls dissolved and many hyphal apices burst. Contact between hyphae was not necessary for lysis to occur. T. koningii produced two endochitinases (Rf 0·15 and 0·24) and two exo-acting chitinolytic enzymes (Rf 0·46 and 0·62) during degradation of crabshell chitin and S. cepivorum cell walls. The Rf 0·24 and 0·46 proteins were detected when T. koningii colonized S. cepivorum-infected roots and are likely to be a component of the antagonism process.
Yawkuen Li - One of the best experts on this subject based on the ideXlab platform.
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effective extraction and purification of β xylosidase from Trichoderma koningii fermentation culture by aqueous two phase partitioning
Enzyme and Microbial Technology, 2001Co-Authors: Yawkuen LiAbstract:Effective extraction of protein from bulk medium is an important technique in bioresearch. In the present study, we describe an extracellular b-xylosidase from the fermentation supernatant of Trichoderma koningii G-39 that was successfully extracted and purified simultaneously in a single step by using an aqueous two-phase partitioning method. This two-phase system was prepared by dissolving suitable amount of poly(ethylene glycol) (PEG) and sodium dihydrogenphosphate (NaH 2PO4) in aqueous solution. b-Xylosidase was recovered with high yield and high concentration in the bottom salt-rich phase when 25% (w/v) PEG 1500 and 20 ‐25% (w/v) NaH 2PO4 were applied. Based on a 1-liter scale extraction, the purity of the enzyme was enhanced at least 33-fold. The total activity increased 422% in comparison with that in the untreated filtrate. The effectiveness and simplicity may make this technique potentially useful in various applications. The transxylosylation activity of the enzyme purified by this technique was also investigated. © 2001 Elsevier Science Inc. All rights reserved.
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effective induction purification and characterization of Trichoderma koningii g 39 β xylosidase with high transferase activity
Biotechnology and Applied Biochemistry, 2000Co-Authors: Yawkuen LiAbstract:: A beta-xylosidase was induced and purified from the culture filtrate of Trichoderma koningii G-39, grown in a medium containing 1% oat spelts xylan and 0.1% xylose. The presence of xylose unequivocally enhanced the induction of beta-xylosidase. The purified enzyme, which exhibited a significant alpha-arabinosidase activity, was obtained with high yield simply via ethanol precipitation and a single anion-exchange chromatography and was characterized as a monomeric glycoprotein with an estimated molecular mass of 104 kDa and a pI of 4.6. The K(m) values towards p-nitrophenyl beta-D-xylopyranoside and p-nitrophenyl alpha-L-arabinopyranoside are 0.04 and 7.5 mM, respectively. It is stable at pH 2.5-7.4, 37 degrees C. The pH and temperature optima are in the range of 3.5-4.0 and 55-60 degrees C, respectively. Contrary to most beta-xylosidases from other sources, Hg(2+) (up to 25 mM) has no effect on enzyme activity. Xylose was shown to inhibit the purified enzyme with a moderate K(i) value of 5 mM. The enzyme exhibited transxylosylation activity and was characterized as a 'retaining' enzyme, catalysing the hydrolysis of substrate with the retention of anomeric configuration.
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mechanistic study of beta xylosidase from Trichoderma koningii g 39
Journal of Biochemistry, 2000Co-Authors: Yawkuen LiAbstract:: The catalytic mechanism of the beta-xylosidase purified from the culture filtrate of Trichoderma koningii G-39 was investigated. By NMR spectroscopy, the stereochemistry of the enzyme catalyzing the hydrolysis of 2,4-dinitrophenyl and p-nitrophenyl-beta-D-xylosides was found unequivocally to involve retention of the anomeric configuration. Based on the k(cat) values of a series of arylxylosides with leaving group pK(a)s in the range of 4-10, an extended Bronsted plot was constructed with a slope (beta(lg)) near zero. Enzymatic hydrolysis of aryl-beta-D-xylosides in acetate buffer (pH 4.0) containing 3 or 5% methanol showed a constant product ratio (methylxyloside/xylose), indicating the presence of a common intermediate, probably the xylosyl-enzyme intermediate. In the presence of DTT, the k(cat) values of p-cyanophenyl-beta-D-xylopyranoside and p-nitrophenyl-beta-D-xylopyranoside increased greatly. A two-step mechanism involving the formation and breakdown of the xylosyl-enzyme intermediate was therefore proposed. The rate-limiting step is the breakdown of the intermediate. The secondary deuterium kinetic isotope effect (k(H)/k(D)) measured for 2,4-dinitrophenyl-beta-D-xyloside was 1.02+/-0.01, suggesting that the transition state for breakdown of the xylosyl-enzyme intermediate is S(N)2-like.
D A Metcalf - One of the best experts on this subject based on the ideXlab platform.
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effect of inoculum density of sclerotium cepivorum on the ability of Trichoderma koningii to suppress white rot of onion
Plant Disease, 2004Co-Authors: D A Metcalf, J J C Dennis, C R WilsonAbstract:ABSTRACT Amendment of soil with Trichoderma koningii strain Tr5 grown on autoclaved white millet grain provided between 63 and 79% control of white rot of onion when added to soil containing 10, 25, 50, or 100 sclerotia of Sclerotium cepivorum per kilogram of soil at the time of onion seed sowing. There was no significant difference in the proportion of S. cepivorum infections suppressed among the different sclerotial density treatments. Rhizosphere colonization by T. koningii Tr5 was assessed by incubating onion roots sampled from plants growing in soil with the appropriate density of sclerotia, on a Trichoderma selective medium (Rose bengall-Allisan-streptomycin-Previcur agar) developed for the purpose of the study. Trichoderma spp. isolated were typed by comparison of culture morphology as well as polygalacturonase (PG) (EC 3.2.1.15) and pectinesterase (PE) (EC 3.1.1.11) isozyme profiles to the series of one PG and two PE isozymes known to be produced by T. koningii Tr5. The method was used successfull...
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the process of antagonism of sclerotium cepivorum in white rot affected onion roots by Trichoderma koningii
Plant Pathology, 2001Co-Authors: D A Metcalf, C R WilsonAbstract:Trichoderma koningii (strain Tr5) grew in the epidermal mucilage of onion roots without entering healthy epidermal tissue. When placed on the epidermis of Sclerotium cepivorum-infected roots, T. koningii colonized epidermal passage cells, with little colonization of other epidermal tissues, then branched and spread throughout the root cortical tissues damaged by enzymes and toxins which diffused ahead of S. cepivorum hyphae, and impeded the path of the infection. When T. koningii colonized infected tissue, many S. cepivorum hyphae became detached at septa, cell walls dissolved and many hyphal apices burst. Contact between hyphae was not necessary for lysis to occur. T. koningii produced two endochitinases (Rf 0·15 and 0·24) and two exo-acting chitinolytic enzymes (Rf 0·46 and 0·62) during degradation of crabshell chitin and S. cepivorum cell walls. The Rf 0·24 and 0·46 proteins were detected when T. koningii colonized S. cepivorum-infected roots and are likely to be a component of the antagonism process.
Sueli Rodrigues - One of the best experts on this subject based on the ideXlab platform.
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optimization of chitosanase production by Trichoderma koningii sp under solid state fermentation
Food and Bioprocess Technology, 2012Co-Authors: Luis Antonio Da Silva, Talita L Honorato, Telma Teixeira Franco, Sueli RodriguesAbstract:This study aimed at the optimization of the production of chitosanase in solid culture. Trichoderma koningii sp., an entomopathogenic fungus, was used to produce chitosanase under solid-state fermentation using a mixture of wheat bran and chitosan. The incubation period; addition of moistening water and culture medium composition were optimized. The protocol to extract the enzyme was also optimized. The optimal conditions for chitosanase production by T. koningii were obtained using a mixture of 3.0 g of wheat bran and 1.5 g of chitosan, with the addition of 2.5 mL of moistening water (pH 5.5) and of 2.5 mL of saline solution (pH 5.5) containing NaNO3 (1.0 g/L), (NH4)2HPO4 (1.0 g/L), MgSO4.7H2O (1.0 g/L), and NaCl (1.0 g/L). Optimal enzyme extraction was carried out adding 20 mL of sodium acetate buffer (200 mM, pH 5.5) at 30 °C under orbital agitation at 150 rpm for 6 min. The optimized production yielded 4.84 IU/gds.
Zhang Yuzhong - One of the best experts on this subject based on the ideXlab platform.
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broad spectrum antimicrobial activity and high stability of trichokonins from Trichoderma koningii smf2 against plant pathogens
Fems Microbiology Letters, 2006Co-Authors: Song Xiaoyan, Shen Qingtao, Xie Shutao, Chen Xiulan, Sun Caiyun, Zhang YuzhongAbstract:Antimicrobial metabolites produced by Trichoderma koningii SMF2 exhibited antimicrobial activity against a range of Gram-positive bacterial and fungal phytopathogens. Purification of these metabolites was achieved using combinations of gel filtration and high-performance liquid chromatography. Identified by liquid chromatography electrospray ionization tandem mass spectrometry, the active metabolites proved to be three known peptaibols: Trichokonin VI, VII and VIII. The Trichokonins were stable and remained biological active over a wide pH range and at every temperature tested, showing no loss of activity even after autoclaving. Trichokonins were insensitive to proteolytic enzymes. Trichokonin VI takes on typical helical structure and the structure changes only slightly at different temperatures and pH values. The present study presented the potential of Trichokonins to be used as biological control agents.
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acute toxicity of Trichoderma koningii smf2 spores and extracellular metabolites
Agrochemicals, 2006Co-Authors: Zhang YuzhongAbstract:Acute oral toxicity testing in white mice, and skin and eye irritation studies in rabbits were conducted with spores and extracellular metabolites of Trichoderma koningii SMF2. Spores and extracellular metabolites of T. koningii SMF2 were not toxic to mice, and did not cause skin irritation in rabbits. Extracellular metabolites caused no rabbit eye irritation, but spores were slightly irritating. These results provide a basis for approval and widespread use of T. koningii SMF2 as a green biopesticide.
