| 1. |
- Cheilas, T, et al.
(författare)
-
Hemicellulolytic activity of Fusarium oxysporum grown on sugar beet pulp. Production of extracellular arabinanase
- 2000
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Ingår i: Process Biochemistry. - 1359-5113 .- 1873-3298. ; 35:6, s. 557-561
-
Tidskriftsartikel (refereegranskat)abstract
- Fusarium oxysporum F3 exhibited hemicellulolytic enzymic activity when grown on sugar beet pulp, a by-product of the sugar industry. The growth medium was specifically optimised for enhanced production of extracellular arabinanase. The optimum medium contained sugar beet pulp (4%, w/v) and corn steep liquor (6%, v/v) as carbon and nitrogen sources, respectively. Arabinanase activity as high as 0.25 U/ml of culture was obtained, which compared favourably to those reported for other microorganisms. Optimal arabinanase activity was observed at pH 6-7 and 50 °C. Investigation of the degradation of the main components of sugar beet pulp showed that arabinose containing polysaccharides and pectin were first degraded, followed by the glucose-containing polysaccharides.
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| 2. |
- Kalogeris, E., et al.
(författare)
-
Application of different processes for the biodegradation of 1,3-dichloro-2-propanol by the bacterium Pseudomonas putida DSM 437
- 2007
-
Ingår i: Chemical and biochemical engineering quarterly. - 0352-9568 .- 1846-5153. ; 21:3, s. 297-305
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Tidskriftsartikel (refereegranskat)abstract
- 1,3-Dichloro-2-propanol (1,3-DCP), is a highly toxic compound used in many industrialprocesses. Biodegradation of 1,3-DCP, by the bacterial strain Pseudomonasputida DSM 347, was studied applying three different processes. A number of combinations,with respect to glucose and 1,3-DCP concentration were examined during batchprocess. When the initial concentration of 1,3-DCP was 600 mg L–1 in the presence of400 mg L–1 glucose, the biodegradation degree and rate were 10.8 % and 0.68 mg L–1h–1 respectively. 1,3-DCP biodegradation by the resting cells of P. putida DSM 347 wastested at mass concentrations from = 200 to 1 000 mg L–1 using biomass concentrationof 5 g dry cell mass L–1. Biodegradation of 1,3-DCP ranged from 84 to 90 %, initialbiodegradation rates ranged from r = 2.36 to 10.55 mg L–1 h–1, while dependence of bothparameters from the initial concentration of halohydrin was observed. A system of twoContinuous Stirred Tank Reactors (CSTRs) in series was developed for the biodegradationof a highly toxic stream of 1,3-DCP (2000 mg L–1). The overall biodegradationdegree of the system was 68 %, while biodegradation rates of the first and secondbioreactor were r = 2.88 and 5.21 mg L–1 h–1 respectively.
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| 3. |
- 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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| 4. |
- Christakopoulos, Paul, et al.
(författare)
-
Direct conversion of straw to ethanol by Fusarium oxysporum : Effect of cellulose crystallinity
- 1991
-
Ingår i: Enzyme and microbial technology. - 0141-0229 .- 1879-0909. ; 13:3, s. 272-274
-
Tidskriftsartikel (refereegranskat)abstract
- Wheat straw was successfully fermented to ethanol by Fusarium oxysporum F3 in a one-step process. Cellulose crystallinity was found to be a major factor in the bioconversion process. Ethanol yields increased linearly with decreasing crystallinity index. Approximately 80% of straw carbohydrates were converted directly to ethanol with a yield of 0.28 g ethanol/g−1 of straw when the crystallinity index was reduced to 23.6%.
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| 5. |
- Christakopoulos, Paul, et al.
(författare)
-
Direct ethanol conversion of pretreated straw by Fusarium oxysporum
- 1991
-
Ingår i: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 35:3, s. 297-300
-
Tidskriftsartikel (refereegranskat)abstract
- Factors affecting the direct conversion of alkali pretreated straw to ethanol by Fusarium oxysporum F3 were investigated and the alkali level used for pretreatment and the degree of delignification of straw were found to be the most important. A linear correlation between ethanol yield and both the degree of straw delignification and the alkali level was observed. At optimum delignified straw concentration (4% w/v), a maximum ethanol yield of 0·275 g ethanol g−1 of straw was obtained corresponding to 67·8% of the theoretical yield.
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| 6. |
- Christakopoulos, Paul, et al.
(författare)
-
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
-
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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| 7. |
- Christakopoulos, Paul, et al.
(författare)
-
Production and partial characterization of xylanase from Fusarium oxysporum
- 1996
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Ingår i: Bioresource Technology. - 0960-8524 .- 1873-2976. ; 58:2, s. 115-119
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Tidskriftsartikel (refereegranskat)abstract
- Production of xylanase by Fusarium oxysporum strain F3 was enhanced by optimization of initial pH of the culture medium, the type and concentration of nitrogen and carbon source, and the growth temperature. Under these conditions, yields as high as 245 U/ml of culture medium were obtained. The most important characteristic of the enzyme is its high pH stability. It retained 80 and 66% of the activity at pH 9.0 after 24 h at 4 and 30°C, respectively. 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, one minor xylanase and one active β-xylosidase exhibiting pI values of 9.5, 6.5 and 3.8, respectively
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| 8. |
- Christakopoulos, Paul, et al.
(författare)
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Production of an esterase from Fusarium oxysporum catalysing transesterification reactions in organic solvents
- 1998
-
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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| 9. |
- Christakopoulos, Paul, et al.
(författare)
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Purification and characterization of an extracellular α-L- arabinofuranosidase from Fusarium oxysporum
- 2000
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Ingår i: Applied Biochemistry and Biotechnology. - 0273-2289 .- 1559-0291. ; 87:2, s. 127-133
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Tidskriftsartikel (refereegranskat)abstract
- An α-L-arabinofuranosidase from Fusarium oxysporum F3 was purified to homogeneity by a two-step ion exchange intercalated by a gel filtration chromatography. The enzyme had a molecular mass of 66 kDa and was optimally active at pH 6.0 and 60°C. It hydrolyzed aryl α-L-arabinofuranosides and cleaved arabinosyl side chains from arabinoxylan and arabinan. There was a marked synergistic effect between the α-L-arabinofuranosidase and an endo-(1→4)-β-D-xylanase produced by F. oxysporum in the extensive hydrolysis of arabinoxylan.
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| 10. |
- Hatzinikolaou, D.G, et al.
(författare)
-
Comparative growth studies of the extreme thermophile Sulfolobus acidocaldarius in submerged and solidified substrate cultures
- 2001
-
Ingår i: World Journal of Microbiology & Biotechnology. - 0959-3993 .- 1573-0972. ; 17:3, s. 229-234
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Tidskriftsartikel (refereegranskat)abstract
- An attempt was made, for the first time, to exploit cultures on solidified substrates (SSC) as an alternative to submerged cultures (SmC) for growing extremophilic micro-organisms. The extreme thermophilic archaebacterium Sulfolobus acidocaldarius was grown on a number of carbon sources and, in all experiments, biomass yields and growth rates were always higher in SSC than in the corresponding SmC. Inoculum age significantly affected growth characteristics on both types of fermentation. Heavy growth of the micro-organism in SSC was observed on low-cost carbon sources such as starch. Wheat bran significantly enhanced growth characteristics when used to supplement starch media. The results of this work show that cultures on solid surfaces could be a promising alternative method for growing extreme thermophiles.
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| 11. |
- Hatzinikolaou, D.G, et al.
(författare)
-
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
-
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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| 12. |
- Kalogeris, E., et al.
(författare)
-
Properties of catechol 1,2-dioxygenase from Pseudomonas putida immobilized in calcium alginate hydrogels
- 2006
-
Ingår i: Enzyme and microbial technology. - : Elsevier BV. - 0141-0229 .- 1879-0909. ; 39:5, s. 1113-1121
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Tidskriftsartikel (refereegranskat)abstract
- Catechol 1,2-dioxygenase from Pseudomonas putida was isolated and immobilized in calcium alginate hydrogels. The gel matrix could effectively entrap the enzyme, with high retention of activity. Following immobilization, catechol 1,2-dioxygenase exhibited improved storage stability and activity in the presence of organic solvents, and performed better at higher incubation temperatures. In addition, the enzyme retained most of its catalytic efficiency after successive operational cycles. The hypothesis that enhancement of enzyme stability after immobilization is related to the stabilization of its multimeric structure has been investigated. Electron paramagnetic resonance (EPR) spectroscopy indicates that the environment of the non-heme iron center was not affected during the immobilization process and the ability for the substrate (catechol) binding at the metal center was retained. Catalytic constants for free and immobilized enzyme were practically equivalent. The influence of internal and external mass-transfer limitations on the initial reaction rates of dioxygenase-catalyzed oxidation reactions has been investigated.
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| 13. |
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| 14. |
- Koullas, D.P., et al.
(författare)
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Effect of alkali delignification on wheat straw saccharification by fusarium oxysporum cellulases
- 1993
-
Ingår i: Biomass and Bioenergy. - 0961-9534 .- 1873-2909. ; 4:1, s. 9-13
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Tidskriftsartikel (refereegranskat)abstract
- The effect of alkaline delignification of wheat straw on the chemical composition and the subsequent enzymic hydrolysis of the pretreated straw are reported. Both hot (120°°C) and cold (20–36°°C) delignification were investigated, using either aqueous or organic alkaline solutions. The treated lignocellulosic materials were hydrolyzed by the cellulases of Fusarium oxysporum strain F3. Both delignification and saccharification yield showed linear relationships with the level of alkali used. Under the chosen experimental conditions 70–100% hydrolysis was achieved either by hot or cold delignification. Delignification to at least 50% appeared crucial for total polysaccharide conversion.
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| 15. |
- Mamma, D., et al.
(författare)
-
Combined photo-assisted and biological treatment of industrial oily wastewater
- 2004
-
Ingår i: Journal of Environmental Science and Health. Part A. - 1093-4529 .- 1532-4117. ; 39:3, s. 729-740
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Tidskriftsartikel (refereegranskat)abstract
- In the present study an oily wastewater from the lubricant unit of a petroleum company was evaluated by combining the sequence photo-assisted oxidation-Pseudomonas putida DSM 437. The wastewater contained various alcohols, acids and phenolic compounds. From the above mentioned compounds the biodegradation of ethylene glycol, phenol, o-cresol and p-cresol was examined. The direct biodegradation of the wastewater using P. putida DSM 437 resulted in 95% ethylene glycol assimilation while phenol, o-cresol and p-cresol assimilation was in the range of 27% to 40%. In order to increase the degradation of the phenolic compounds photo-assisted oxidation was applied to the wastewater using UV/H2O2 as a pretreatment step to biological degradation. Fe(III) were used in order to accelerate the formation of the hydroxyl radicals and consequently the overall photo-oxidation process. The addition of Fe(III) ions resulted in 30% decrease of COD within the first 10 min while the respected value without iron ions was 5%. he combined photo-assisted oxidation and biodegradation of the wastewater resulted in 100% removal of ethylene glycol. The overall degradation of phenol was 78% while the 59% and 84% of the initial o-cresol and p-cresol respectively, were removed from the wastewater. The-combined process resulted in 72% of COD removal.
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| 16. |
- 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
-
Ingår i: Biomass and Bioenergy. - : Elsevier BV. - 0961-9534 .- 1873-2909. ; 10:4, s. 213-219
-
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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| 17. |
- Tsitsimpikou, C., et al.
(författare)
-
Studies of the effect of organic solvents on the stability of β-glucosidase from Fusarium oxysporum
- 1994
-
Ingår i: Biotechnology letters. - 0141-5492 .- 1573-6776. ; 16:1, s. 57-62
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of organic solvents on the stability of β-glucosidase in a powder form, isolated fromFusarium oxysporum, has been studied using several organic solvents of different degree of hydrophobicity. It was found that β-glucosidase remains quite stable after a prolonged incubation in the presence of most of the organic solvents used, even at temperatures as high as 70°C. Only dimethyformamide (DMF) and tetrahydrofuran (THF) reduce considerably the enzyme activity in a short preincubation period. Studies on the effect of the pH of the buffer used prior to lyophilization, as well as of exogenous added water to the incubation mixture, on enzyme stability show that it is more stable in pH 5.0 and in the lowest water content. In addition it was found that the presence of glucose in the lyophilization procedure gives a significant protection to the enzyme when it is incubated for 30 h in pentanol and n-hexane.
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| 18. |
- Agnantiari, G., et al.
(författare)
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A Purified α-galactosidase from aspergillus niger with enhanced kinetic characteristics
- 1991
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Ingår i: Acta Biotechnologica. - : Wiley. - 0138-4988 .- 1521-3846. ; 11:5, s. 479-484
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Tidskriftsartikel (refereegranskat)abstract
- Extracellular α-galactosidase from Aspergillus niger was purified 128-fold over the crude extract by gel filtration, ion exchange chromatography and chromatofocusing. Certain substrates and end products affected enzyme activity. Among the former p-nitrophenyl-α-galactopyranoside (PNPG) inhibited the enzyme at 1.4 mM while melibiose did not inhibit α-galactosidase at concentrations up to 50 mM. Enzymic end products such as glucose did not inhibit the enzyme at concentrations up to 100 mM while galactose exhibited a competitive inhibition with a Ki = 1.29 mM. The kinetic characteristics of the enzyme compared favourably to other microbial α-galactosidases and make it suitable for food process applications.
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| 19. |
- Christakopoulos, Paul, et al.
(författare)
-
Antimicrobial activity of acidic xylo-oligosaccharides produced by family 10 and 11 endoxylanases
- 2003
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Ingår i: International Journal of Biological Macromolecules. - 0141-8130 .- 1879-0003. ; 31:4-5, s. 171-175
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Tidskriftsartikel (refereegranskat)abstract
- Acidic oligosaccharides were obtained from birchwood xylan by treatment with a Thermoascus aurantiacus family 10 and a Sporotrichum thermophile family 11 endoxylanases. The main difference between the products liberated by xylanases of family 10 and 11 concerned the length of the products containing 4-O-methyl-d-glucuronic acid. The xylanase from T. aurantiacus liberate from glucuronoxylan an aldotetrauronic acid as the shortest acidic fragment in contrast with the enzyme from S. thermophile, which liberated an aldopentauronic acid. Acidic xylooligosaccharides were separated from the hydrolysate by anion-exchange and size-exclusion chromatography (SEC) and the primary structure was determined by 13C NMR spectroscopy. The acidic xylo-oligosaccharides were tested against three Gram-positive and three Gram-negative aerobically grown bacteria, as well as against Helicobacterpylori. Aldopentauronic acid was proved more active against the Gram-positive bacteria and against H. pylori.
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| 20. |
- 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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| 21. |
- Christakopoulos, Paul, et al.
(författare)
-
Direct fermentation of cellulose to ethanol by Fusarium oxysporum
- 1989
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Ingår i: Enzyme and microbial technology. - : Elsevier BV. - 0141-0229 .- 1879-0909. ; 11:4, s. 236-239
-
Tidskriftsartikel (refereegranskat)abstract
- The cellulase hyperproducing strain F3 of Fusarium oxysporum fermented glucose, xylose, cellobiose, and cellulose directly to ethanol. Conversion of cellulose to ethanol was markedly affected by the pH of both aerated preculture and nonaerated fermentation. Optimum values of cellulose conversion to ethanol were obtained when aerated and nonaerated processes were carried out at pH 5.5 and 6, respectively. Maximum ethanol concentrations of 9.6 and 14.5 g l−1, corresponding to 89.2 and 53.2% of the theoretical yield, were obtained when the fungus was grown under nonaerated conditions at 34°C for 6 days in a medium containing 20 and 50 g l−1cellulose, respectively.
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| 22. |
- Christakopoulos, Paul, et al.
(författare)
-
Exceptionally thermostable α- and β-galactosidase from Aspergillus niger separated in one step
- 1990
-
Ingår i: Process Biochemistry. - 1359-5113 .- 1873-3298. ; 25:6, s. 210-212
-
Tidskriftsartikel (refereegranskat)abstract
- Extracellular alpha- and-beta-galactosidases from a strain of Aspergillus niger were separated and purified in one step by cation exchange chromatography. Both enzymes had acidic pH (3.5-4.0) and high temperature (65-degrees-C) optima and an exceptionally high thermostability. Thus, -alpha-galactosidase had an activity half-time of 104 min at 60-degrees-C whereas at the same temperature the respective value for-beta-galactosidase was 835 min. At optimum conditions of activity the apparent K(m) values of alpha- and beta-galactosidase were 0.44mM and 1.1mM respectively. Both the high temperature optima and thermostability properties of the enzymes make them particularly suitable for high temperature processes.
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| 23. |
- Christakopoulos, Paul, et al.
(författare)
-
Functional characterization of a cellulose binding xylanase from Fusarium oxysporum
- 1996
-
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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| 24. |
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| 25. |
- Christakopoulos, Paul, et al.
(författare)
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On the mechanism of direct conversion of cellulose to ethanol by Fusarium oxysporum : Effect of cellulase and β-glucosidase
- 1990
-
Ingår i: Applied Microbiology and Biotechnology. - 0175-7598 .- 1432-0614. ; 33:1, s. 18-20
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Tidskriftsartikel (refereegranskat)abstract
- The effects of the three main enzymes involved in cellulose saccharification, namely cellobiohydrolase, carboxymethylcellulase and beta-glucosidase, on the direct conversion of cellulose to ethanol by Fusarium oxysporum F3 were investigated. Ethanol production was not affected when the activity of the former two enzymes was varied within a wide range. By contrast, beta-glucosidase markedly affected ethanol production showing an optimum level of 0.7-0.8 unit/ml growth medium. A significant decrease of cellulose bioconversion time to ethanol was obtained when beta-glucosidase activity was adjusted to this optimal level at the beginning of the fermentation process.
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| 26. |
- Christakopoulos, Paul, et al.
(författare)
-
Purification and characterization of a less randomly acting endo-1,4-beta-D-glucanase from the culture filtrates of Fusarium oxysporum
- 1995
-
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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| 27. |
- Christakopoulos, Paul, et al.
(författare)
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Purification and characterization of two low molecular mass alkaline xylanases from Fusarium oxysporum F3
- 1996
-
Ingår i: Journal of Biotechnology. - : Elsevier BV. - 0168-1656 .- 1873-4863. ; 51:2, s. 181-189
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Tidskriftsartikel (refereegranskat)abstract
- Two low molecular mass endo-1,4-β-d-xylanases from Fusarium oxysporum were purified to homogeneity by gel-filtration and ion-exchange chromatography. They exhibit molecular masses of 20.8 (xylanase I) and 23.5 (xylanase II) kDa, and isoelectric points of 9.5 and 8.45–8.70, respectively. Both xylanases display remarkable pH (9.0) stability. At 40 to 55 °C xylanase II is more thermostable than xylanase I but less active on xylan. In contrast to xylanase I, xylanase II is able to hydrolyze 1-O-4-methylumbelliferyl-(β-d-glucopyranosyl)-β-d-xylopyranoside (muxg). Neither of these enzymes hydrolyze xylotriose. They bind on crystalline cellulose but not on insoluble xylan. Analysis of reaction mixtures by high pressure liquid chromatography revealed that both enzymes cleave preferentially the internal glycosidic bonds of xylopentaose and oat spelts xylan. Thus the purified enzymes appeared to be true endo-β-1,4-xylanases. The amino terminal sequences of xylanases I and II show no homology. Xylanase I shows high similarity with alkaline low molecular mass xylanases of family G/11.
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| 28. |
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| 29. |
- 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
-
Ingår i: Journal of Biotechnology. - : Elsevier BV. - 0168-1656 .- 1873-4863. ; 39:1, s. 85-93
-
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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| 30. |
- Hatzinikolaou, Dimitris G., et al.
(författare)
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Modeling of the simultaneous hydrolysis-ultrafiltration of whey permeate by a thermostable beta-galactosidase from Aspergillus niger
- 2005
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Ingår i: Biochemical engineering journal. - : Elsevier BV. - 1369-703X .- 1873-295X. ; 24:2, s. 161-172
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Tidskriftsartikel (refereegranskat)abstract
- A wild type strain of Aspergillus niger, denoted as BTL, produced elevated levels of β-galactosidase when grown in a low cost medium that contained wheat bran as the sole carbon and energy source. The enzyme was collected, concentrated and partially purified from the culture supernatant. Its kinetic and stability properties were thoroughly examined towards its potential use for the hydrolysis of acid whey permeate lactose. The β-galactosidase of A. niger BTL showed increased pH and thermal stability, with activation energy for the first order deactivation constant equal to 180 kJ/mol at pH 3.5. Lactose hydrolysis by the enzyme was described by Michaelis–Menten kinetics with competitive inhibition only from galactose. An integrated process, concerning the simultaneous hydrolysis–ultrafiltration of whey lactose that incorporated the specific kinetic properties of the β-galactosidase was developed and modeled. The model proved very successful in predicting the behavior of a continuous laboratory hydrolysis–ultrafiltration set up, specifically designed for that purpose. The validated model was finally used in a number of computer simulations in order to investigate the effect of the various process parameters on the overall system performance.
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| 31. |
- Kalogeris, E, et al.
(författare)
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Catalytic properties of the endoxylanase I from Thermoascus aurantiacus
- 2001
-
Ingår i: Journal of Molecular Catalysis B. - 1381-1177 .- 1873-3158. ; 11:4-6, s. 491-501
-
Tidskriftsartikel (refereegranskat)abstract
- Endo-β-1,4-xylanase I previously purified from Thermoascus aurantiacus solid state culture was further characterized. The enzyme had a molecular weight of 33 kDa by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and 31 kDa by gel filtration. Thin layer chromatography (TLC) analysis showed that endoxylanase liberates aldotetrauronic acid MeGlcAα-1,2-Xylβ-1,4-Xylβ-1,4-Xyl as the shortest acidic fragment from glucuronoxylan and an isomeric xylotriose (Xyl3) of the structure Xylβ1-3Xylβ1-4Xyl from rhodymenan. The enzyme performed ideally on O-acetyl-4-O-methylglucuronoxylan, liberating large amounts of short acetylated and non-acetylated fragments. Also, the enzyme was capable to hydrolyse arabinoxylan to arabinose (Arab), xylose (Xyl) and xylobiose (Xyl2). The enzyme degraded pNPX (4-nitrophenyl β-D-xylopyranoside) by a complex reaction pathway that involved both hydrolysis and glycosyl transfer reactions. The enzyme tolerates the replacement of β-xylopyranosyl units in several artificial substrates by β-glucopyranosyl, α-L-arabinopyranosyl and α-L-arabinofuranosyl units and was active on pNPC (4-nitrophenyl β-D-cellobioside), pNP-Arap (4-nitrophenyl α-L-arabinopyranoside) and pNPAraf (4-nitrophenyl α-L-arabinofuranoside). The enzyme also hydrolysed the 4-methylumbelliferyl glycosides of β-D-xylobiose and β-D-xylotriose at the agluconic linkage. The results suggested that the xylanase I from T. aurantiacus has catalytic properties similar to those belonging to family 10. Copyright © 2001 Elsevier Science B.V.
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| 32. |
- Kalogeris, E, et al.
(författare)
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Performance of an intermittent agitation rotating drum type bioreactor for solid-state fermentation of wheat straw
- 2003
-
Ingår i: Bioresource Technology. - 0960-8524 .- 1873-2976. ; 86:3, s. 207-213
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Tidskriftsartikel (refereegranskat)abstract
- A laboratory bioreactor, designed for solid-state fermentation of thermophilic microorganisms, was operated for production of cellulases and hemicellulases by the thermophilic fungus Thermoascus aurantiacus. The suitability of the apparatus for the effective control of important operating variables affecting growth of microbes in solid-state cultivation was determined. Application of the optimum conditions found for the moisture content of the medium, growth temperature and airflow rate produced enzyme yields of 1709 U endoglucanase, 4 U cellobiohydrolase, 79 U β-glucosidase, 5.5 U FPA, 4490 U xylanase and 45 U β-xylosidase per g of dry wheat straw. The correlation between microorganism growth and production of enzymes was efficiently described by the Le Duy kinetic model. © 2002 Elsevier Science Ltd. All rights reserved.
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| 33. |
- Kalogeris, E, et al.
(författare)
-
Production and characterization of cellulolytic enzymes from the thermophilic fungus Thermoascus aurantiacus under solid state cultivation of agricultural wastes
- 2003
-
Ingår i: Process Biochemistry. - 1359-5113 .- 1873-3298. ; 38:7, s. 1099-1104
-
Tidskriftsartikel (refereegranskat)abstract
- Extracellular cellulolytic enzymes were produced under solid state cultivation by the thermophilic fungus Thermoascus aurantiacus and characterized. Elevated levels of endoglucanase and β-glucosidase activities were produced simultaneously by optimization of growth factors. Under optimal growth conditions, 1572 U endoglucanase and 101.6 U β-glucosidase per g of carbon source were obtained. Chromogenic (fluorogenic) 4-methylumbelliferyl-β-glycosides of glucose (MUG) and cellobiose (MUG2) were used to characterize the cellulolytic multienzyme components after separation by isoelectric focusing. The zymogram indicated one endoglucanase and one β-glucosidase with pI values 3.5 and 3.9, respectively. Both enzymes exhibited significant thermostability, with half-lives of 42 and 18 min, respectively, at 80°C
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| 34. |
- 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
-
Ingår i: Journal of Biotechnology. - 0168-1656 .- 1873-4863. ; 60:3, s. 155-163
-
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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| 35. |
- Katapodis, P., et al.
(författare)
-
Biosynthesis of fructo-oligosaccharides by Sporotrichum thermophile during submerged batch cultivation in high sucrose media
- 2004
-
Ingår i: Applied Microbiology and Biotechnology. - : Springer Science and Business Media LLC. - 0175-7598 .- 1432-0614. ; 63:4, s. 378-382
-
Tidskriftsartikel (refereegranskat)abstract
- A feruloyl esterase (StFAE-A) produced by Sporotrichum thermophile was purified to homogeneity. The purified homogeneous preparation of native StFAE-A exhibited a molecular mass of 57.0±1.5 kDa, with a mass of 33±1 kDa on SDS-PAGE. The pI of the enzyme was estimated by cation-exchange chromatofocusing to be at pH 3.1. The enzyme activity was optimal at pH 6.0 and 55–60 °C. The purified esterase was stable at the pH range 5.0–7.0. The enzyme retained 70% of activity after 7 h at 50 °C and lost 50% of its activity after 45 min at 55 °C and after 12 min at 60 °C. Determination of k cat/K m revealed that the enzyme hydrolyzed methyl p-coumarate 2.5- and 12-fold more efficiently than methyl caffeate and methyl ferulate, respectively. No activity on methyl sinapinate was detected. The enzyme was active on substrates containing ferulic acid ester linked to the C-5 and C-2 linkages of arabinofuranose and it hydrolyzed 4-nitrophenyl 5-O-trans-feruloyl-α-l-arabinofuranoside (NPh-5-Fe-Araf) 2-fold more efficiently than NPh-2-Fe-Araf. Ferulic acid (FA) was efficiently released from destarched wheat bran when the esterase was incubated together with xylanase from S. thermophile (a maximum of 34% total ferulic acid released after 1 h incubation). StFAE-A by itself could release FA, but at a level almost 47-fold lower than that obtained in the presence of xylanase. The potential of StFAE-A for the synthesis of various phenolic acid esters was tested using a ternary water-organic mixture consisting of n-hexane, 1-butanol and water as a reaction system.
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| 36. |
- Katapodis, P, et al.
(författare)
-
Production of acidic xylo-oligosaccharides by a family 10 endoxylanase from Thermoascus aurantiacus and use as plant growth regulators
- 2002
-
Ingår i: Biotechnology letters. - 0141-5492 .- 1573-6776. ; 24:17, s. 1413-1416
-
Tidskriftsartikel (refereegranskat)abstract
- Neutral and acidic oligosaccharides were obtained from birchwood xylan by treatment with an endoxylanase, family 10 class, from Thermoascus aurantiacus. The main acidic xylooligosaccharide (aldotetrauronic acid) was separated from the hydrolysate by anion-exchange and size-exclusion chromatography and the primary structure was determined by 13C NMR spectroscopy. The aldotetrauronic yield was 15% (w/w) of the total solubilised sugars. The addition of purified aldoterauronic acid at 1.6-16 mg 1 -1 growth medium, induced callus and somatic embryogenesis in culture explants of common mallow (Malva silvestris L.) and cotton (Gosssypium hirsutum).
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| 37. |
- Lezinou, V., et al.
(författare)
-
Simultaneous saccharification and fermentation of sweet sorghum carbohydrates to ethanol in a fed-batch process
- 1994
-
Ingår i: Biotechnology letters. - 0141-5492 .- 1573-6776. ; 16:9, s. 983-988
-
Tidskriftsartikel (refereegranskat)abstract
- The simultaneous saccharification and fermentation (SSF) of sweet sorghum carbohydrates to ethanol by Fusarium oxysporum F3 alone or in mixed culture with Saccharomyces cerevisiae 2541 or Zymomonas mobilis CP4 in a fed-batch fermentation process was studied. While SSF was adequately carried out by the first microorganism the process achieved its maximum value by the mixed culture of the fungus and yeast. Under optimum conditions, ethanol yields and concentrations as high as 29.7 g of ethanol per 100 g of dry sorghum stalk and 7.5 % (w/v) respectively were obtained. These values together with the high yield of sorghum crop in Greece make this process promising and worthy of further investigation for the production of fuel bioethanol
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| 38. |
- Lezinou, V., et al.
(författare)
-
Study of a single and mixed culture for the direct bio-conversion of sorghum carbohydrates to ethanol
- 1995
-
Ingår i: Applied Microbiology and Biotechnology. - 0175-7598 .- 1432-0614. ; 43:3, s. 412-415
-
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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| 39. |
- 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
-
Ingår i: International Journal of Biological Macromolecules. - 0141-8130 .- 1879-0003. ; 22:2, s. 97-101
-
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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| 40. |
- Panagiotou, G, et al.
(författare)
-
Purification and characterisation of NAD+-dependent xylitol dehydrogenase from Fusarium oxysporum
- 2002
-
Ingår i: Biotechnology letters. - 0141-5492 .- 1573-6776. ; 24:24, s. 2089-2092
-
Tidskriftsartikel (refereegranskat)abstract
- An NAD+-dependent xylitol dehydrogenase (XDH) from Fusarium oxysporum, a key enzyme in the conversion of xylose to ethanol, was purified to homogeneity and characterised. It was homodimeric with a subunit of Mr 48 000, and pI 3.6. It was optimally active at 45°C and pH 9-10. It was fully stable at pH 6-7 for 24 h and 30°C. Km values for D-xylitol and NAD+ were 94 mM and 0.14 mM, respectively. Mn2+ at 10 mM increased XDH activity 2-fold and Cu2+ at 10 mM inhibited activity completely.
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| 41. |
- Stamatis, H., et al.
(författare)
-
Studies on the synthesis of short-chain geranyl esters catalysed by Fusarium oxysporum esterase in organic solvents
- 1998
-
Ingår i: Journal of Molecular Catalysis B. - 1381-1177 .- 1873-3158. ; 4:4, s. 229-236
-
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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| 42. |
- Topakas, E., et al.
(författare)
-
Bioconversion of ferulic acid into vanillic acid by the thermophilic fungus Sporotrichum thermophile
- 2003
-
Ingår i: Lebensmittel-Wissenschaft + Technologie. - 0023-6438 .- 1096-1127. ; 36:6, s. 561-565
-
Tidskriftsartikel (refereegranskat)abstract
- Sporotrichum thermophile is capable of promoting the formation of vanillic acid during ferulic acid degradation. Ferulic acid metabolism by S. thermophile apparently occurred via the propenoic chain degradation and the formation of 4-hydroxy-3-methoxystyrene (4-vinylguaiacol) was observed which was presumably metabolized to vanillic acid. Guaiacol was detected in addition to the above-mentioned intermediates, usually as a result of nonoxidative decarboxylation of vanillic acid. The bioconversion of ferulic into vanillic acid was affected by the amount of ferulic acid that was treated and the carbon source on which the biomass was grown. Under optimum conditions vanillic acid production from ferulic acid by S. thermophile attained very high levels of 4798 mg/L with a molar yield of 35%
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| 43. |
- Topakas, E., et al.
(författare)
-
Production of phenolics from corn cobs by coupling enzymic treatment and solid state fermentation
- 2004
-
Ingår i: Engineering in Life Sciences. - : Wiley. - 1618-0240 .- 1618-2863. ; 4:3, s. 283-286
-
Tidskriftsartikel (refereegranskat)abstract
- A two-stage process that combined solid-state fermentation (SSF) and subsequent enzymic treatment was used in order to release p-coumaric (p-CA) and ferulic acid (FA) from corn cobs. Sporotrichum thermophile was grown on corn cobs under SSF conditions, and the production of cinnamoyl esterases and xylanases was studied over 7 days. The time course of enzyme production showed a maximum activity of 1483 nkat/g, 0.3 nkat/g and 0.067 nkat/g for xylanase, feruloyl esterase, and p-coumaroyl esterase, respectively. The importance of the moisture level of the growth substrate was discussed. After SSF, the fermented substrate was directly exposed to autohydrolysis and the in situ produced multienzyme system was successfully used for the partial degradation of cell wall components and the liberation of p-CA and FA. A yield of 0.85 g/kg and 0.38 g/kg FA and p-CA, respectively, of dry matter of corn cobs was obtained.
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| 44. |
- Topakas, E., et al.
(författare)
-
Purification and characterization of a feruloyl esterase from Fusarium oxysporum catalyzing esterification of phenolic acids in ternary water–organic solvent mixtures
- 2003
-
Ingår i: Journal of Biotechnology. - 0168-1656 .- 1873-4863. ; 102:1, s. 33-44
-
Tidskriftsartikel (refereegranskat)abstract
- An extracellular feruloyl esterase (FAE-II) from the culture filtrates of Fusarium oxysporum F3 was purified to homogeneity by SP-Sepharose, t-butyl-HIC and Sephacryl S-200 column chromatography. The protein corresponded to molecular mass and pI values of 27 kDa and 9.9, respectively. The enzyme was optimally active at pH 7 and 45 °C. The purified esterase was fully stable at pH 7.0–9.0 and temperature up to 45 °C after 1 h incubation. Determination of kcat/Km revealed that the enzyme hydrolysed methyl sinapinate 6, 21 and 40 times more efficiently than methyl ferulate, methyl coumarate and methyl caffeate, respectively. The enzyme was active on substrates containing ferulic acid ester linked to the C-5 but inactive to the C-2 positions of arabinofuranose such as 4-nitrophenyl 5-O-trans-feruloyl-α-l-arabinofuranoside and 4-nitrophenyl 2-O-trans-feruloyl-α-l-arabinofuranoside. In the presence of Sporotrichum thermophile xylanase, there was a significant release of ferulic acid from destarched wheat bran by FAE-II, indicating a synergistic interaction between FAE-II and S. thermophile xylanase. FAE-II by itself could release only little ferulic acid from destarched wheat bran. The potential of FAE-II for the synthesis of various phenolic acid esters was tested using as a reaction system a surfactantless microemulsion formed in ternary mixture consisting of n-hexane, 1-propanol and water.
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| 45. |
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| 46. |
- Tsoka, S., et al.
(författare)
-
Time temperatüre integration for chilled food shelf life monitoring using enzyme‐substrate systems
- 1998
-
Ingår i: Food biotechnology. - : Informa UK Limited. - 0890-5436 .- 1532-4249. ; 12:1-2, s. 139-155
-
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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