| 51. |
- Panagiotou, Gianni, et al.
(författare)
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Induction, purification, and characterization of two extracellular alpha-L-arabinofuranosidases from Fusarium oxysporum
- 2003
-
Ingår i: Canadian journal of microbiology (Print). - 0008-4166 .- 1480-3275. ; 49:10, s. 639-644
-
Tidskriftsartikel (refereegranskat)abstract
- In the presence of L-arabinose as sole carbon source, Fusarium oxysporum produces two α-L-arabinofuranosidases (ABFs) named ABF1 and ABF2, with molecular masses of 200 and 180 kDa, respectively. The two F. oxysporum proteins have been purified to homogeneity. The purified enzymes are composed of three equal subunits and are neutral proteins with pIs of 6.0 and 7.3 for ABF1 and ABF2, respectively. With p-nitrophenyl α-L-arabinofuranoside (pNPA) as the substrate, ABF1 and ABF2 exhibited Km values of 0.39 and 0.28 mmol·L–1, respectively, and Vmax values of 1.6 and 4.6 µmol·min–1·(mg of protein)–1, respectively, and displayed optimal activity at pH 6.0 and 50–60 °C. ABFs released arabinose only from sugar beet arabinan and not from wheat soluble and insoluble arabinoxylans. The enzymes were not active on substrates containing ferulic acid ester linked to C-5 and C-2 linkages of pNPA showing that phenolic substituents of pNPA sterically hindered the action of ABFs.Key words: α-L-arabinofuranosidase, enzyme purification, enzyme induction.
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| 52. |
- Panagiotou, Gianni, et al.
(författare)
-
Production of cellulolytic and xylanolytic enzymes by Fusarium oxysporum grown on corn stover in solid state fermentation
- 2003
-
Ingår i: Industrial crops and products (Print). - 0926-6690 .- 1872-633X. ; 18:1, s. 35-47
-
Tidskriftsartikel (refereegranskat)abstract
- Corn stover is an abundant, potential fermentation substrate. Production of cellulolytic and xylanolytic enzymes by the mesophilic fungus Fusarium oxysporum under solid state culture (SSC) on corn stover was enhanced by optimization of the type of nitrogen source, initial moisture level, growth temperature and initial pH of the culture medium. Under these conditions, yields as high as 304, 4.1, 0.140, 1840 and 0.041 U/g of carbon source of endoglucanase, cellobiohydrolase, β-glucosidase, xylanase and β-xylosidase, respectively, were obtained. SCC in a laboratory horizontal bioreactor using the optimized medium allowed the large scale production of the multienzymic system in similar yields. Chromogenic (fluorogenic) 4-methylumbelliferyl β-glycosides of cellobiose and xylobiose were used to characterize the major activities of the multienzyme component, after separation by isoelectric focusing (IEF) electrophoresis. The zymograms indicated one major cellulase and four xylanase activities exhibiting pI values 5 and 5, 6, 7.3, 8.3, respectively.
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| 53. |
- 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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| 54. |
- Papaparaskevas, Dimitris, et al.
(författare)
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Optimizing production of extracellular lipase from Rhodotorula glutinis
- 1992
-
Ingår i: Biotechnology letters. - 0141-5492 .- 1573-6776. ; 14:5, s. 397-402
-
Tidskriftsartikel (refereegranskat)abstract
- Production of extracellular lipase byRhodotorula glutinis was substantially enhanced when the type and concentration of carbon and nitrogen source, the initial pH of culture medium and the growth temperature were consecutively optimized. Lipase activity as high as 30.4 U/ml of culture medium was obtained at optimum conditions, comparing favourably with most of the activities reported for other lipase hyperproducing microorganisms. The enzyme was optimally active at pH 7.5 and 35°C and had, at optimum pH, half-lives of 45 and 11.8 min at 45 and 55°C respectively. The high activity and kinetic characteristics of the enzyme make this process worthy of further investigation.
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| 55. |
- Puchart, Vladimı́r, et al.
(författare)
-
Production of xylanases, mannanases, and pectinases by the thermophilic fungus Thermomyces lanuginosus
- 1999
-
Ingår i: Enzyme and microbial technology. - 0141-0229 .- 1879-0909. ; 24:5-6, s. 355-361
-
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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| 56. |
- 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
-
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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| 57. |
- 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
-
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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| 58. |
- 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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| 59. |
- Topakas, Evangelos, et al.
(författare)
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Production and partial characterisation of feruloyl esterase by Sporotrichum thermophile in solid-state fermentation
- 2003
-
Ingår i: Process Biochemistry. - 1359-5113 .- 1873-3298. ; 38:11, s. 1539-1543
-
Tidskriftsartikel (refereegranskat)abstract
- A number of factors affecting production of feruloyl esterase an enzyme that hydrolyse ester linkages of ferulic acid (FA) in plant cell walls, by the thermophylic fungus Sporotrichum thermophile under solid state fermentation (SSF) were investigated. Initial moisture content and type of carbon source were consecutively optimised. SSF in a laboratory horizontal bioreactor using the optimised medium allowed the production of 156 mU g−1 of carbon source, which compared favourably with those reported for the other micro-organisms. Optimal esterase activity was observed at pH 8 and 60 °C. The activity of the esterase was measured on an insoluble feruloylated hemicellulose substrate (de-starched wheat bran (DSWB)). De-esterification of wheat straw yielded loss of feruloyl esterase production even though the supplementation of free FA comparable to the alkali-extractable levels of FA found in wheat straw. Chromogenic (fluorogenic) 4-methylumbelliferyl ferulate was used to characterise the multienzyme component, after separation by isoelectric focusing and native PAGE electrophoresis. The zymograms indicated one major esterase activity exhibiting pI and molecular mass values 5 and 27 kDa, respectively.
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| 60. |
- Topakas, Evangelos, et al.
(författare)
-
Production and partial characterization of xylanase from Sporotrichum thermophile under solid-state fermentation
- 2003
-
Ingår i: World Journal of Microbiology & Biotechnology. - 0959-3993 .- 1573-0972. ; 19:2, s. 195-198
-
Tidskriftsartikel (refereegranskat)abstract
- A number of factors affecting production of xylanase, by the thermophilic fungus Sporotrichum thermophile under solid state fermentation (SSF) were investigated. Initial moisture content and type of carbon source were consecutively optimized. Solid state fermentation in a laboratory horizontal bioreactor using the optimized medium allowed the production of 320 U g−1 of carbon source which compared favourably with those reported for other microorganisms. Optimal xylanase activity was observed at pH 5 and 70 °C. Chromogenic (fluorogenic) 4-methylumbelliferyl β-glycoside of xylobiose (MUX2) was used to characterize the xylanase multienzyme component, after separation by isoelectric focusing and native PAGE electrophoresis. The zymograms indicated one major xylanase fraction exhibiting pI and molecular mass values 4 and 90–120 kDa, respectively.
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| 61. |
- 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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| 62. |
- 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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| 63. |
- Topakas, Evangelos, et al.
(författare)
-
Purification and characterization of a Fusarium oxysporum feruloyl esterase (FoFAE-I) catalysing transesterification of phenolic acid esters
- 2003
-
Ingår i: Enzyme and microbial technology. - 0141-0229 .- 1879-0909. ; 33:5, s. 729-737
-
Tidskriftsartikel (refereegranskat)abstract
- An extracellular feruloyl esterase (FoFAE-I) from the culture filtrates of Fusarium oxysporum F3 was purified to homogeneity by ion-exchange, hydrophobic interaction and gel filtration chromatographies. The protein corresponded to molecular mass and pI values of 31 kDa and 9.5, respectively. The enzyme was optimally active at pH 7.0 and 55 °C. The purified esterase was fully stable at pH 7.0–9.0 and temperature up to 30 °C. Determination of kcat/Km revealed that the enzyme hydrolysed methyl p-coumarate (MpCA) 4.5, 9, and 239 times more efficiently than methyl caffeate (MCA), methyl ferulate (MFA) and methyl sinapinate (MSA), respectively. The enzyme was active on substrates containing ferulic acid ester linked to the C-5 and C-2 linkages of arabinofuranose but showed preference for the ester at position 2. 4-Nitrophenyl-2-O-trans-feruloyl-α-l-arabinofuranoside (NPh-5-Fe-Araf) was hydrolysed 100 times more efficiently than 4-nitrophenyl-5-O-trans-feruloyl-α-l-arabinofuranoside (NPh-2-Fe-Araf). Ferulic acid (FA) was efficiently released from destarched wheat bran (DSWB) when the esterase was incubated together with xylanase from Sporotrichum thermophile (a maximum of 92% total ferulic acid released after 4 h incubation). FoFAE-I by itself could release FA but at a level almost five-fold lower than that obtained in the presence of xylanase. The potential of FAE-I for the synthesis of various phenolic acid esters was tested using as a reaction system a surfactantless microemulsions formed in ternary mixture consisting of n-hexane, 1-butanol and water.
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| 64. |
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| 65. |
- Tsitsimpikou, C., et al.
(författare)
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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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| 66. |
- Tsoka, S., et al.
(författare)
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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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| 67. |
- Vardakou, M., et al.
(författare)
-
Synergy between enzymes involved in the degradation of insoluble wheat flour arabinoxylan
- 2004
-
Ingår i: Innovative Food Science & Emerging Technologies. - 1466-8564 .- 1878-5522. ; 5:1, s. 107-112
-
Tidskriftsartikel (refereegranskat)abstract
- Two microbial endo-β-1,4-xylanases (EXs, EC 3.2.1.8) belonging to glycanase families 10 and 11 were examined for their ability to release ferulic acid (FA) from water-unextractable arabinoxylan (WU-AX) in the presence of a feruloyl esterase (FoFAE-II) from Fusarium oxysporum. WU-AX was incubated with different levels of a Thermoascus aurantiacus family 10 (XYLI) and a Sporotrichum thermophile family 11 (XYLA) endoxylanases. At 10 g/l arabinoxylan, enzyme concentrations (KE values) needed to obtain half-maximal hydrolysis rates for FA release were 0.18 and 0.44 nM for the xylanases from T. aurantiacus and S. thermophile, respectively. Determination of Vmax/KE revealed that the family 10 enzyme performed 4.3 times more efficiently than the family 11 enzyme in liberation of FA when a feruloyl esterase is present. Molecular weights of the products formed were assessed and separation of feruloyl-oligosaccharides was achieved by anion-exchange and size-exclusion chromatography (SEC). The results showed that the degradation of the xylan backbone was influenced strongest by the action of xylanases while the presence of the esterase mainly resulted in the release of ferulic acid from the produced short chain feruloylated xylo-oligosaccharides by the action of xylanases
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