| 1. |
- Cheilas, T, et al.
(författare)
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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
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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)
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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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| 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. |
- Anasontzis, George E, 1980, et al.
(författare)
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Constitutive homologous expression of phosphoglucomutase and transaldolase increases the metabolic flux of Fusarium oxysporum
- 2014
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Ingår i: Microbial Cell Factories. - : Springer Science and Business Media LLC. - 1475-2859. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: Fusarium oxysporum is among the few filamentous fungi that have been reported of being able to directly ferment biomass to ethanol in a consolidated bioprocess. Understanding its metabolic pathways and their limitations can provide some insights on the genetic modifications required to enhance its growth and subsequent fermentation capability. In this study, we investigated the hypothesis reported previously that phosphoglucomutase and transaldolase are metabolic bottlenecks in the glycolysis and pentose phosphate pathway of the F. oxysporum metabolism.Results: Both enzymes were homologously overexpressed in F. oxysporum F3 using the gpdA promoter of Aspergillus nidulans for constitutive expression. Transformants were screened for their phosphoglucomutase and transaldolase genes expression levels with northern blot. The selected transformant exhibited high mRNA levels for both genes, as well as higher specific activities of the corresponding enzymes, compared to the wild type. It also displayed more than 20 and 15% higher specific growth rate upon aerobic growth on glucose and xylose, respectively, as carbon sources and 30% higher biomass to xylose yield. The determination of the relative intracellular amino and non-amino organic acid concentrations at the end of growth on glucose revealed higher abundance of most determined metabolites between 1.5- and 3-times in the recombinant strain compared to the wild type. Lower abundance of the determined metabolites of the Krebs cycle and an 68-fold more glutamate were observed at the end of the cultivation, when xylose was used as carbon source.Conclusions: Homologous overexpression of phosphoglucomutase and transaldolase in F. oxysporum was shown to enhance the growth characteristics of the strain in both xylose and glucose in aerobic conditions. The intracellular metabolites profile indicated how the changes in the metabolome could have resulted in the observed growth characteristics. © 2014 Anasontzis et al.; licensee BioMed Central Ltd.
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| 5. |
- Christakopoulos, Paul, et al.
(författare)
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Enhanced acetyl esterase production by Fusarium oxysporum
- 1999
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Ingår i: World Journal of Microbiology & Biotechnology. - 0959-3993 .- 1573-0972. ; 15:4, s. 443-446
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Tidskriftsartikel (refereegranskat)abstract
- Production of acetyl esterase (EC 3.1.1.6) by Fusarium oxysporum strain F3 was enhanced by optimization of growth conditions. Under optimal conditions, activities as high as 0.89 U/ml of culture medium were obtained. The culture filtrate was equally active on p-nitrophenyl acetate and acetylxylan. The enzyme produced 71% deacetylation of acetylxylan in 2 h at 40 ∘C. Activity was optimized at pH6.5 and at 55 ∘C. The respective Km values for p-nitrophenyl acetate and acetylxylan were 0.25 mM and 1.05% (w/v) and the Vm values were 0.65 and 0.43 μmol acetate/min/mg protein.
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| 6. |
- Christakopoulos, Paul, et al.
(författare)
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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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| 7. |
- Christakopoulos, Paul, et al.
(författare)
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Production of an esterase from Fusarium oxysporum catalysing transesterification reactions in organic solvents
- 1998
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Ingår i: Process Biochemistry. - 1359-5113 .- 1873-3298. ; 33:7, s. 729-733
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Tidskriftsartikel (refereegranskat)abstract
- The production of an esterase by Fusarium oxysporum, grown on tomato skins as the sole carbon source, was studied in submerged and solid state cultures. Under optimum growth conditions, enzyme yields as high as 7·3 U/ml of culture medium and 19·4 U/g of carbon source were obtained. The esterase catalysed the synthesis of esters in organic solvents. Geraniol was transacetylated in hexane by the esterase using triacetyl as an acetyl donor. The geranyl acetate yield was 68%.
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| 8. |
- 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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| 9. |
- Mamma, D., et al.
(författare)
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Combined photo-assisted and biological treatment of industrial oily wastewater
- 2004
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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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| 10. |
- 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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| 11. |
- Kourtoglou, E., et al.
(författare)
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Purification, characterization and mass spectrometric sequencing of transaldolase from Fusarium oxysporum
- 2008
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Ingår i: Process Biochemistry. - : Elsevier BV. - 1359-5113 .- 1873-3298. ; 43:10, s. 1094-1101
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Tidskriftsartikel (refereegranskat)abstract
- Transaldolase (FoTal) was purified to homogeneity from the fungus Fusarium oxysporum. The native enzyme revealed a monomeric structure with molecular mass of 36 kDa. This FoTal depicted an optimal pH of 7.5 using imidazole buffer, while loss of activity was observed with Tris/HCl buffer. The optimal temperature was between 40 and 45 °C and the enzyme became unstable at temperatures above 50 °C. The isoelectric point of the purified enzyme was 4.5. The kinetics of the purified enzyme is consistent with a Ping Pong mechanism. The Km values for d-erythrose-4-phosphate and d-fructose-6-phosphate were 0.49 and 6.66 mM, while the kcat values were estimated at 4114 and 4151 min-1, respectively. LC-MS/MS analysis provided peptide mass and sequence information that facilitated primary structure confirmation, allowing us to identify the FoTal gene (foxg_03074) from the genome of F. oxysporum.
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| 12. |
- Mamma, D., et al.
(författare)
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Citrus peels : an excellent raw material for the bioconversion into value-added products
- 2008
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Ingår i: Tree and Forestry Science and Biotechnology. - 1752-3753. ; 2:1, s. 83-97
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Tidskriftsartikel (refereegranskat)abstract
- Citrus by-products are the processing wastes generated after citrus juice extraction and constitute about 50% of fresh fruit weight. This solid residue is comprised of the peel (flavedo and albedo), pulp (juice sac residue), rag (membranes and cores) and seeds. The disposal of fresh peels is becoming a major problem for many factories. Usually, citrus juice industries dry the residue and it is either sold as raw material for pectin extraction or pelletized for animal feeding, though none of these processes is very profitable. This residual material is a poor animal feed supplement because of its extremely low protein content and high amount of sugar. The application of agroindustrial by-products in bioprocesses offers a wide range of alternative substrates, thus helping to solve pollution problems related to their disposal. Attempts have been made to use citrus by-products to generate several value-added products, such as enzymes, single cell protein, natural antioxidants, ethanol, organic acids, polysaccharides and prebiotics. This article reviews developments regarding processes and products that have employed citrus peels as a substrate for biotechnological applications.
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| 13. |
- Sanakis, Y., et al.
(författare)
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Catechol 1,2-dioxygenase from Pseudomonas putida in organic media : an electron paramagnetic resonance study
- 2003
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Ingår i: International Journal of Biological Macromolecules. - 0141-8130 .- 1879-0003. ; 33:1-3, s. 101-106
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Tidskriftsartikel (refereegranskat)abstract
- The ability of an isolated isozyme of catechol 1,2-dioxygenase from Pseudomonas putida DSM 437 to function in a non-aqueous environment was investigated. The lyophilized enzyme is able to keep its catalytic function catalyzing the oxidation of catechol in n-hexane. Electron paramagnetic resonance (EPR) spectroscopy at liquid helium temperatures was applied to compare the properties of the non-heme iron of the enzyme in the organic solvent and in the aqueous solution. The catalytic performance of the enzyme in the organic solvent is correlated with the spectroscopic properties of the non-heme iron.
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