| 1. |
- Bennett, Neil A., et al.
(författare)
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Biochemical and catalytic properties of an endoxylanase purified from the culture filtrate of Thermomyces lanuginosus ATCC 46882
- 1998
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Ingår i: Carbohydrate Research. - 0008-6215 .- 1873-426X. ; 306:3, s. 445-455
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Tidskriftsartikel (refereegranskat)abstract
- An endoxylanase (1,4-beta-D-xylan xylanohydrolase, EC 3.2.1.8) from the culture filtrates of T. lanuginosus ATCC 46882 was purified to homogeneity by DEAE-Sepharose and Bio-Gel P-30 column chromatographies. The purified endoxylanase had a specific activity of 888.8 mumol min-1 mg-1 protein and accounted for approximately 30% of the total protein secreted by this fungus. The molecular mass of native (non-denatured) and denatured endoxylanase were 26.3 and 25.7 kD as, respectively. Endoxylanase had a pI of 3.7 and was optimally active between pH 6.0-6.5 and at 75 degrees C. The enzyme showed > 50% of its original activity between pH 5.5-9.0 and at 85 degrees C. The pH and temperature stability studies revealed that this endoxylanase was almost completely stable between pH 5.0-9.0 and up to 60 degrees C for 5 h and at pH 10.0 up to 55 degrees C for 5 h. Thin-layer chromatography (TLC) analysis showed that endoxylanase released mainly xylose (Xyl) and xylobiose (Xyl2) from beechwood 4-O-methyl-D-glucuronoxylan, O-acetyl-4-O-methyl-D-glucuronoxylan and rhodymenan (a beta-(1-->3)-beta(1-->4)-xylan). Also, the enzyme released an acidic xylo-oligosaccharide from 4-O-methyl-D-glucuronoxylan, and an isomeric xylotetraose and an isomeric xylopentaose from rhodymenan. The enzyme hydrolysed [1-3H]-xylo-oligosaccharides in an endofashion, but the hydrolysis of [1-3H]-xylotriose appeared to proceed via transglycosylation. since the xylobiose was the predominant product. Endoxylanase was not active on pNPX and pNPC at 40 and 100 mM for up to 6 h, but showed some activity toward pNPX at 100 mM after 20-24 h. The results suggested that the endoxylanase from T. lanuginosus belongs to family 11.
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| 2. |
- Christakopoulos, Paul, et al.
(författare)
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Controlling simultaneous production of endoglucanase and beta-glucosidase by Fusarium oxysporum in submerged culture
- 1995
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Ingår i: Biotechnology letters. - 0141-5492 .- 1573-6776. ; 17:8, s. 883-888
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Tidskriftsartikel (refereegranskat)abstract
- The simultaneous production of endoglucanase and β-glucosidase by Fusarium oxysporum was investigated in submerged culture. Consecutive optimization of growth conditions resulted in the correction of large activity differences, observed during production of enzymes, and substantially enhanced low enzyme yields. At optimum growth conditions yields as high as 1650 and 232 U per g of carbon source of endoglucanase and β-glucosidase were obtained respectively competing favourably with those reported for microorganisms grown on the same carbon source. The most important kinetic characteristics of the enzymes were the high temperature optima of endoglucanase (60°C) and β-glucosidase (65°C) and the exceptionally high thermostability of endoglucanase. The latter enzyme retained 50% of the activity at pH 5.0 after approximately 6.5 h at 70°C
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| 3. |
- Christakopoulos, Paul, et al.
(författare)
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Enhanced acetyl esterase production by Fusarium oxysporum
- 1999
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Ingår i: World Journal of Microbiology & Biotechnology. - 0959-3993 .- 1573-0972. ; 15:4, s. 443-446
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Tidskriftsartikel (refereegranskat)abstract
- Production of acetyl esterase (EC 3.1.1.6) by Fusarium oxysporum strain F3 was enhanced by optimization of growth conditions. Under optimal conditions, activities as high as 0.89 U/ml of culture medium were obtained. The culture filtrate was equally active on p-nitrophenyl acetate and acetylxylan. The enzyme produced 71% deacetylation of acetylxylan in 2 h at 40 ∘C. Activity was optimized at pH6.5 and at 55 ∘C. The respective Km values for p-nitrophenyl acetate and acetylxylan were 0.25 mM and 1.05% (w/v) and the Vm values were 0.65 and 0.43 μmol acetate/min/mg protein.
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| 4. |
- Christakopoulos, Paul, et al.
(författare)
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Enhancement of pH-stability of a low molecular mass endoglucanase from Fusarium oxysporum by protein pegylation
- 1998
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Ingår i: Carbohydrate Research. - 0008-6215 .- 1873-426X. ; 314:1-2, s. 95-99
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Tidskriftsartikel (refereegranskat)abstract
- The stability of the low molecular mass endoglucanase (23.2 kDa) from Fusarium oxysporum at alkaline pH was enhanced by chemical modification. Two distinct types of amino acid-specific modifiers were used. The first, either cyanuric chloride activated polyethylene glycol (CC–PEG) or polyethylene glycol succinimidyl succinate active ester (SS–PEG), react (more or less specifically) with protein amino groups. The second type, maleimide polyethylene glycol (Mal–PEG), is specific for cysteinyl residues. The enzyme lost almost all of its activity when modified with CC–PEG, whereas no inactivation was observed with SS–PEG and Mal–PEG. The modified endoglucanase showed remarkably enhanced alkaline pH stability. When acting upon cello-oligosaccharides and 4-methylumbelliferyl cello-oligosaccharides, the enzyme preferentially cleaved the internal glycosidic bonds. The modified enzymes mediated a decrease in the viscosity of carboxymethyl cellulose (CMC) associated with the release of only small amounts of reducing sugar. Thus, the modified enzyme retains the endo character of the native enzyme
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| 5. |
- Christakopoulos, Paul, et al.
(författare)
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Functional characterization of a cellulose binding xylanase from Fusarium oxysporum
- 1996
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Ingår i: Biotechnology letters. - 0141-5492 .- 1573-6776. ; 18:3, s. 349-354
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Tidskriftsartikel (refereegranskat)abstract
- An extracellular endoxylanase from Fusarium oxysporum binds onto crystalline cellulose. A small peptide (~ 2kDa) could be isolated after partial proteolysis of the native protein. It consists of 18 amino acids, is located in the C-terminal region of the protein and corresponds functionally to a cellulose binding domain (CBD), the first one to be reported in a fungal xylanase. The amino acid sequence of this peptide shows no homology with any known CBD
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| 6. |
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| 7. |
- Christakopoulos, Paul, et al.
(författare)
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Production of an esterase from Fusarium oxysporum catalysing transesterification reactions in organic solvents
- 1998
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Ingår i: Process Biochemistry. - 1359-5113 .- 1873-3298. ; 33:7, s. 729-733
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Tidskriftsartikel (refereegranskat)abstract
- The production of an esterase by Fusarium oxysporum, grown on tomato skins as the sole carbon source, was studied in submerged and solid state cultures. Under optimum growth conditions, enzyme yields as high as 7·3 U/ml of culture medium and 19·4 U/g of carbon source were obtained. The esterase catalysed the synthesis of esters in organic solvents. Geraniol was transacetylated in hexane by the esterase using triacetyl as an acetyl donor. The geranyl acetate yield was 68%.
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| 8. |
- Christakopoulos, Paul, et al.
(författare)
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Purification and characterisation of a major xylanase with cellulase and transferase activities from Fusarium oxysporum
- 1996
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Ingår i: Carbohydrate Research. - : Elsevier BV. - 0008-6215 .- 1873-426X. ; 289, s. 91-104
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Tidskriftsartikel (refereegranskat)abstract
- A major xylanase from Fusarium oxysporum was purified to homogeneity by gel filtration, affinity, and ion-exchange chromatographies. It has a molecular mass of 60.2 kDa and pl of 6.6 and was optimally active at pH 7.4 and at 50 °C. The enzyme was stable over the pH range 5.8–8.2 at 40 °C for 24 h and lost 45% of its original activity at pH 9.0 under the identical conditions. The enzyme rapidly hydrolysed xylans from oat spelts (husks) and birchwood, but the activities on carboxymethylcellulose (CMC), filter paper, and Avicel were very low. Determination of kcat/Km revealed that the enzyme hydrolysed oat spelts and birchwood xylans, 15–30 times more efficiently than CMC. In a 24 h incubation, at pH 7.0 and 9.0, the enzyme hydrolysed oat spelts and birchwood xylans by 75 and 65%, respectively. However, at pH 7.0, the enzyme released almost equal amounts of xylose and xylobiose from both xylans, whereas at pH 9.0, the concentration of xylobiose was twice as muchi as that of xylose and xylotriose. Xylanase attacked preferentially the internal glycosidic bonds of xylo- and 4-methylumbelliferyl cello-oligosaccharides [MeUmb(Glc)n]. The enzyme catalysed transglycosylation reaction with xylotriose, xylotetraose, and xylopentaose as donors and 4-methylumbelliferyl β-d-glucoside (MeUmbGlc) as an acceptor.
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| 9. |
- Christakopoulos, Paul, et al.
(författare)
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Purification and characterization of a less randomly acting endo-1,4-beta-D-glucanase from the culture filtrates of Fusarium oxysporum
- 1995
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Ingår i: Archives of Biochemistry and Biophysics. - : Elsevier BV. - 0003-9861 .- 1096-0384. ; 316:1, s. 428-433
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Tidskriftsartikel (refereegranskat)abstract
- An extracellular endo-1,4-β-D-glucanase from Fusarium oxysporum was purified by affinity chromatography and gel filtration. The enzyme purified in this way was homogeneous when judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and isoelectric focusing-polyacrylamide gel electrophoresis. The protein corresponded to a molecular mass and pI value of 41.7 kDa and 6.4, respectively. It was optimally active at pH 4.5 and at 55°C. The enzyme hydrolyzed carboxymethylcellulose (CMC) and unsubstituted and substituted cello-oligosaccharides but was inactive on Avicel, filter paper, xylan, cellobiose, p-nitrophenyl-β-D-glucoside, and p-nitrophenyl-β-D-xyloside. However, the enzyme effected only a small change in viscosity of CMC per unit increase of reducing sugar. When cellotriose, cellotetraose, and cellopentaose were used as substrates, the enzyme released mainly cellobiose. Use of 4-methylumbelliferyl cello-oligosaccharides and the determination of bond cleavage frequency revealed that the enzyme preferentially hydrolyzed the glycosidic bond adjacent to 4-methylumbelliferone. Thus, the purified enzyme appeared to be a less randomly acting endoglucanase.
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| 10. |
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| 11. |
- Christakopoulos, Paul, et al.
(författare)
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Purification and mode of action of a low molecular mass endo-1,4-β-d-glucanase from Fusarium oxysporum
- 1995
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Ingår i: Journal of Biotechnology. - : Elsevier BV. - 0168-1656 .- 1873-4863. ; 39:1, s. 85-93
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Tidskriftsartikel (refereegranskat)abstract
- A low molecular mass (23.2 kDa) endo-1,4-β-d-glucanase from Fusarium oxysporum was purified to homogeneity by gel-filtration and ion-exchange chromatographies. The enzyme was optimally active at pH 6.0 and at 50 ° C. It had a pI value of 8.6 and was stable at 55 ° C for 1 h. It hydrolyzed carboxymethylcellulose, cello-oligosaccharides (Glcn) and 4-methylumbelliferylcello-oligosaccharides but did not hydrolyze cellobiose, p-nitrophenyl β-o-glucoside, p-nitrophenyl β-d-xyloside, Avicel, filter paper and xylan. Analysis of reaction mixtures by high pressure liquid chromatography revealed that this enzyme cleaved preferentially the internal glycoside bonds of higher cello-oligosaccharides. The enzyme also catalyzed the formation of transfer products in the presence of cellotriose, cellotetraose and 4-methylumbelliferylglucoside (MeUmbGlc).
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| 12. |
- Christakopoulos, Paul, et al.
(författare)
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Purification and mode of action of an alkali-resistant endo-1,4-β-glucanase from Bacillus pumilus
- 1999
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Ingår i: Archives of Biochemistry and Biophysics. - : Elsevier BV. - 0003-9861 .- 1096-0384. ; 364:1, s. 61-66
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Tidskriftsartikel (refereegranskat)abstract
- Alkaline endo-1,4-β-d-glucanase was secreted byBacillus pumilusgrown in submerged culture on a combination of oat spelt xylan and corn starch as carbon sources. The enzyme was purified to homogeneity by Sephacryl S-200 and Q-Sepharose column chromatography. The protein corresponded to molecular mass and pIvalues of 67 kDa and 3.7, respectively. The enzyme was optimally active at pH 7.0–8.0 and 60°C and retained 50% of its optimum activity at pH 12. The most notable characteristic of the endoglucanase was its high stability up to pH 12 for 20 h at 30°C. The enzyme hydrolyzed carboxymethylcellulose (CMC) and cello-oligosaccharides but was inactive on cellobiose, cellotriose, Avicel, xylan, 4-nitrophenyl-β-d-glucoside, 4-nitrophenyl-β-d-cellobioside, and 4-nitrophenyl-β-d-xyloside. Analysis of reaction mixtures by HPLC revealed that the enzyme produced almost exclusively cellotriose when acted on CMC and appeared to hydrolyze cello-oligosaccharides by successively releasing cellotriose. The use of 4-methylumbelliferyl cello-oligosaccharides and the determination of bond cleavage frequency revealed that the enzyme preferentially hydrolyzed the third glycosidic bond adjacent to the glycon. The enzyme mediated a decrease in the viscosity of CMC associated with a release of only small amounts of reducing sugar. The enzyme activity was not inhibited by metal ions, surfactants, and chelating agents used as components of laundry detergents.
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| 13. |
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| 14. |
- Hatzinikolaou, D.G, et al.
(författare)
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Production and partial characterisation of extracellular lipase from aspergillus niger
- 1996
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Ingår i: Biotechnology letters. - 0141-5492 .- 1573-6776. ; 18:5, s. 547-552
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Tidskriftsartikel (refereegranskat)abstract
- The production and certain kinetic characteristics of extracellular lipase from Aspergillus niger were investigated. It was possible to substantially enhance the activity of excreted lipase by optimising the interaction between carbon and nitrogen sources applying a two-parameter complete experimental design and response surface analysis. The enzyme was partially purified and a number of kinetic characteristics such as optimum pH and temperature, thermal and pH stability and K(m) were determined and discussed. The elevated levels of lipase activity (40.5 U/ml) found in this work competed favourably with most of those reported for lipase hyperproducing fungi.
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| 15. |
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| 16. |
- Kalogeris, E., et al.
(författare)
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Studies on the solid-state production of thermostable endoxylanases from Thermoascus aurantiacus : Characterization of two isozymes
- 1998
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Ingår i: Journal of Biotechnology. - 0168-1656 .- 1873-4863. ; 60:3, s. 155-163
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Tidskriftsartikel (refereegranskat)abstract
- Production of xylanases by the thermophilic fungus Thermoascus aurantiacus under solid state culture (SSC) was enhanced by optimization of the type of carbon and nitrogen source, inoculum type, moisture level and particle size of the carbon source. Under these conditions, yields as high as 6193 U g−1 of carbon source were obtained. Chromogenic (fluorogenic) 4-methylumbelliferyl-β-glycosides of xylose (MUX) and xylobiose (MUX2) were used to characterize xylanase multienzyme components, after separation by isoelectric focusing. The zymogram indicated one major and two minor xylanases and one β-xylosidase. The major (xylanase I) and one of the minor (xylanase II) xylanases were separated and characterized. Both xylanases exhibited remarkable thermostability.
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| 17. |
- Lezinou, V., et al.
(författare)
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Study of a single and mixed culture for the direct bio-conversion of sorghum carbohydrates to ethanol
- 1995
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Ingår i: Applied Microbiology and Biotechnology. - 0175-7598 .- 1432-0614. ; 43:3, s. 412-415
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Tidskriftsartikel (refereegranskat)abstract
- Fusaium oxysporum F3 alone or in mixed culture with Saccharomyces cerevisiae 2541 fermented soluble and insoluble carbohydrates of sweet sorghum stalk directly to ethanol. Both microorganisms were first grown aerobically and fermented sorghum stalk to ethanol thereafter. During fermentation, insoluble carbohydrates were hydrolysed to soluble sugars by the celluloytic system of F. oxysporum. Ethanol yields as high as 24.4 and 33.5 g/100 g dry stalks were obtained by F. oxysporum and the mixed culture respectively, representing a theoretical yield enhancement of 11.6% and 53.6% respectively. The corresponding ethanol concentrations in the fermentation medium were 4.6% and 6.4% (w/v). These results clearly demonstrated that a large portion of insoluble carbohydrate from sorghum was converted by simultaneous saccharification and fermentation to ethanol, making the process promising for bioethanol production.
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| 18. |
- Makropoulou, M., et al.
(författare)
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Factors affecting the specificity of beta-glucosidase from Fusarium oxysporum in enzymatic synthesis of alkyl-beta-D-glucosides
- 1998
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Ingår i: International Journal of Biological Macromolecules. - 0141-8130 .- 1879-0003. ; 22:2, s. 97-101
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Tidskriftsartikel (refereegranskat)abstract
- Factors affecting the specificity of β-glucosidase from Fusarium oxysporum in enzymatic synthesis of alkyl-β-d-glucosidesFusarium oxysporumβ-glucosidase has been used to catalyze the production of alkyl-β-d-glucosides from various disaccharides, based on the transglucosylation reaction, in the presence of primary, secondary and tertiary alcohols as glucosyl acceptors. Primary alcohols were found to be the best acceptors. The influence of the glucosyl donor concentration, as well as the enzyme specificity towards the cleaved glucosidic bond and the aglucone part of the donor, have also been investigated. The enzyme does not exhibit regiospecificity and seems to be unspecific towards the aglucone part. The specificity of the β linkage has been confirmed by proton nuclear magnetic resonance (1H NMR) analysis.
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| 19. |
- Mamma, D., et al.
(författare)
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An alternative approach to the bioconversion of sweet sorghum carbohydrates to ethanol
- 1995
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Ingår i: Biomass and Bioenergy. - 0961-9534 .- 1873-2909. ; 8:2, s. 99-103
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Tidskriftsartikel (refereegranskat)abstract
- The ethanol fermentation of juice and press cake, resulting from the squeezing of sweet sorghum stalks at high pressure, was investigated. The juice was fermented by Saccharomyces cerevisiae and yielded 4.8 g ethanol per 100 g of fresh stalks. The press cake was fermented directly to ethanol by a mixed culture of Fusarium oxysporum and Saccharomyces cerevisiae and yielded 5.1 g ethanol per 100 g of fresh stalks. An overall ethanol concentration and yield of 5.6% (w/v) and 9.9 g of ethanol per 100 g of fresh stalks respectively was obtained. Based on soluble carbohydrates, the ethanol yield from press cake was doubled while the overall theoretical yield was enhanced by 20.7% due to the bioconversion of a significant portion of cell wall polysaccharides to ethanol. The process was found promising for further investigation.
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| 20. |
- Puchart, Vladimı́r, et al.
(författare)
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Production of xylanases, mannanases, and pectinases by the thermophilic fungus Thermomyces lanuginosus
- 1999
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Ingår i: Enzyme and microbial technology. - 0141-0229 .- 1879-0909. ; 24:5-6, s. 355-361
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Tidskriftsartikel (refereegranskat)abstract
- A group of 17 strains of the thermophilic fungus Thermomyces lanuginosus was examined for the production of xylanases, β-mannanases, arabinanases, and pectinases. All strains were found to be xylanolytic, and several were proven to be outstanding producers of microbial xylanase on glucuronoxylan and corn cobs. The strains hyperproducing xylanase secreted low amounts of xylan-debranching enzymes and did not produce β-mannan and arabinan-degrading enzyme systems. Only the strains showing lower xylanase production exhibited a higher degree of xylan utilization and also the ability to produce a mannanolytic enzyme system. One of the mannanolytic strains was found to be capable of producing arabinan-degrading enzymes. This strain also showed the best production of pectinolytic enzymes during growth on citrus pectin or sugar beet pulp. Some of the strains have good potential for use as sources of important industrial enzymes of high thermal stability.
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| 21. |
- Stamatis, H., et al.
(författare)
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Studies on the synthesis of short-chain geranyl esters catalysed by Fusarium oxysporum esterase in organic solvents
- 1998
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Ingår i: Journal of Molecular Catalysis B. - 1381-1177 .- 1873-3158. ; 4:4, s. 229-236
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Tidskriftsartikel (refereegranskat)abstract
- A novel esterase isolated from Fusarium oxysporum was investigated for the synthesis of short-chain esters of geraniol by alcoholysis and direct esterification reactions in organic solvents. The enzyme was used as a dried powder (i.e., not immobilized). The reaction parameters affecting the enzyme behavior such as the nature of organic solvent and acyl donor, the concentration of substrates and the water activity of the system were studied. High yields (80–90%) were obtained by both approaches (alcoholysis and direct esterification) at low values of water activity (aw=0.11) in n-hexane. The enzyme retain its catalytic activity even after fifth reuse in n-hexane at aw=0.11, demonstrating its stability and efficiency under the conditions of this study.
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| 22. |
- Tarantili, P.A., et al.
(författare)
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Cross-synergism in enzymatic hydrolysis of lignocellulosics : Mathematical correlations according to a hyperbolic model
- 1996
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Ingår i: Biomass and Bioenergy. - : Elsevier BV. - 0961-9534 .- 1873-2909. ; 10:4, s. 213-219
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Tidskriftsartikel (refereegranskat)abstract
- The effect of cross-synergism in enzymatic hydrolysis of ball-milled Avicell, alkali-treated straw cellulose (ATSC), cotton and filter paper was investigated using mixtures of Fusarium oxysporum and Neurospora crassa enzymes. The experimental data were fitted according to an empirical hyperbolic model which utilized two parameters, the maximum conversion (xmax) and the enzymatic hydrolysis time corresponding to 50% of xmax (). The model can predict conversion of polysaccharides as a function of hydrolysis time. Both model parameters were found to be strongly dependent on the crystallinity index as well as on the degree of delignification of the substrate. Up to 60% cellulose hydrolysis can be achieved when the crystallinity index of Avicell is reduced from 94.8% to 63.3%. The percentage increase of xmax due to delignification was higher than the corresponding increase of . The extent of cross-synergism depends strongly on crystallinity index and degree of delignification. This type of synergism has been found to be significant in the case of substrates which are resistant to hydrolysis, such as Avicell (with high crystallinity index) or cotton. Cross-synergistic phenomena caused by enzymatic mixtures can double cellulose hydrolysis yield with delignified straw as compared to the hydrolysis yields achieved by single-microorganism cellulases.
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| 23. |
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| 24. |
- Tsoka, S., et al.
(författare)
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Time temperatüre integration for chilled food shelf life monitoring using enzyme‐substrate systems
- 1998
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Ingår i: Food biotechnology. - : Informa UK Limited. - 0890-5436 .- 1532-4249. ; 12:1-2, s. 139-155
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Tidskriftsartikel (refereegranskat)abstract
- Time Temperature Integrators (TTI) are simple devices to monitor temperature exposure history and relate it to food shelf life behaviour. Four colorimetric enzyme reaction systems are proposed as the basis for TTI use and results for their kinetic characterisation under isothermal conditions are presented. Nonisothermal experiments have shown that the proposed system response reflected accurately the dynamic nature of the environment temperature. The reliability of the proposed TTI systems was demonstrated by a case study on chilled fish shelf life prediction after storage temperature abuse.
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