| 1. |
- 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
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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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| 2. |
- Topakas, E., et al.
(författare)
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Bioconversion of ferulic acid into vanillic acid by the thermophilic fungus Sporotrichum thermophile
- 2003
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Ingår i: Lebensmittel-Wissenschaft + Technologie. - 0023-6438 .- 1096-1127. ; 36:6, s. 561-565
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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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| 3. |
- Topakas, E., et al.
(författare)
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Production of phenolics from corn cobs by coupling enzymic treatment and solid state fermentation
- 2004
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Ingår i: Engineering in Life Sciences. - : Wiley. - 1618-0240 .- 1618-2863. ; 4:3, s. 283-286
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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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| 4. |
- Christakopoulos, Paul, et al.
(författare)
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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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| 5. |
- Christov, L, et al.
(författare)
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Effects of purified endo-β-1,4-xylanases of family 10 and 11 and acetyl xylan esterases on eucalypt sulfite dissolving pulp
- 2000
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Ingår i: Journal of Biotechnology. - 0168-1656 .- 1873-4863. ; 83:3, s. 231-244
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Tidskriftsartikel (refereegranskat)abstract
- Sulfite dissolving pulp from Eucalyptus grandis contained approximately 3.8% O-acetyl-4-O-methylglucuronoxylan with a molar ratio of xylose:4-O-methylglucuronic acid:acetyl group close to 13.6:1:6.2. The effects produced by purified endo-xylanases from two different glycosyl hydrolase families (family 10 and 11) as well as acetyl xylan esterases were examined and assessed on pulp in relation to their bleaching abilities. The purified endo-xylanases hydrolyzed only a limited portion (less than 30%) of the acetylglucuronoxylan present in the pulp. The enzymes of family 10 produced acetylated xylobiose and xylotriose whereas acetylated xylobiose was not observed among the products released from the pulp by the family 11 xylanases. The esterases however were not capable of deacetylating the acetylated aldouronic acids generated by the xylanases. Regardless of the different mode of action of the endo-xylanases on dissolving pulp, their effect on pulp bleaching was not related to the amount and nature of sugars generated or the glycosyl hydrolase family. No additional brightness gain was obtained when endo-xylanases were used in conjunction with acetyl xylan esterases, suggesting that the latter do not play an important role in biobleaching of eucalypt sulfite dissolving pulps. Copyright (C) 2000 Elsevier Science B.V. Sulfite dissolving pulp from Eucalyptus grandis contained approximately 3.8% O-acetyl-4-O-methylglucuronoxylan with a molar ratio of xylose:4-O-methylglucuronic acid:acetyl group close to 13.6:1:6.2. The effects produced by purified endo-xylanases from two different glycosyl hydrolase families (family 10 and 11) as well as acetyl xylan esterases were examined and assessed on pulp in relation to their bleaching abilities. The purified endo-xylanases hydrolyzed only a limited portion (less than 30%) of the acetylglucuronoxylan present in the pulp. The enzymes of family 10 produced acetylated xylobiose and xylotriose whereas acetylated xylobiose was not observed among the products released from the pulp by the family 11 xylanases. The esterases however were not capable of deacetylating the acetylated aldouronic acids generated by the xylanases. Regardless of the different mode of action of the endo-xylanases on dissolving pulp, their effect on pulp bleaching was not related to the amount and nature of sugars generated or the glycosyl hydrolase family. No additional brightness gain was obtained when endo-xylanases were used in conjunction with acetyl xylan esterases, suggesting that the latter do not play an important role in biobleaching of eucalypt sulfite dissolving pulps.
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| 6. |
- Hatzinikolaou, D.G, et al.
(författare)
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Comparative growth studies of the extreme thermophile Sulfolobus acidocaldarius in submerged and solidified substrate cultures
- 2001
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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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| 7. |
- Kalogeris, E., et al.
(författare)
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Application of different processes for the biodegradation of 1,3-dichloro-2-propanol by the bacterium Pseudomonas putida DSM 437
- 2007
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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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| 8. |
- Kalogeris, E, et al.
(författare)
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Catalytic properties of the endoxylanase I from Thermoascus aurantiacus
- 2001
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Ingår i: Journal of Molecular Catalysis B. - 1381-1177 .- 1873-3158. ; 11:4-6, s. 491-501
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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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| 9. |
- Kalogeris, E, et al.
(författare)
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Production and characterization of cellulolytic enzymes from the thermophilic fungus Thermoascus aurantiacus under solid state cultivation of agricultural wastes
- 2003
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Ingår i: Process Biochemistry. - 1359-5113 .- 1873-3298. ; 38:7, s. 1099-1104
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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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| 10. |
- Kalogeris, E., et al.
(författare)
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Properties of catechol 1,2-dioxygenase from Pseudomonas putida immobilized in calcium alginate hydrogels
- 2006
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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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| 11. |
- 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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| 12. |
- Katapodis, P., et al.
(författare)
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Biosynthesis of fructo-oligosaccharides by Sporotrichum thermophile during submerged batch cultivation in high sucrose media
- 2004
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Ingår i: Applied Microbiology and Biotechnology. - : Springer Science and Business Media LLC. - 0175-7598 .- 1432-0614. ; 63:4, s. 378-382
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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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