| 1. |
- Gkargkas, Konstantinos, et al.
(författare)
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Studies on a N-acetyl-β-d-glucosaminidase produced by Fusarium oxysporum F3 grown in solid-state fermentation
- 2004
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Ingår i: Process Biochemistry. - 1359-5113 .- 1873-3298. ; 39:11, s. 1599-1605
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Tidskriftsartikel (refereegranskat)abstract
- Fusarium oxysporum F3 produced N-acetyl-β-d-glucosaminidase when grown on wheat bran and chitin as carbon sources in solid-state fermentation. The initial moisture content and pH of growth medium were 65% and 6.0, respectively, and the enzyme yield 23.6 U g−1 carbon source. Two isozymes of N-acetyl-β-d-glucosaminidase, called N-acetyl-β-d-glucosaminidases I and II, were isolated from the culture filtrate of F. oxysporum F3. The filtrate was subjected to ammonium sulphate fractionation followed by anion exchange, gel filtration, hydrophobic interaction and cation exchange chromatography. The optimum pH of isozymes I and II was 5.0 and 6.0, respectively, whereas maximum activity of both isozymes was obtained at 40 °C. The Km of isozymes I and II was 49.6 and 48.6 μM and the Vmax 1.24 and 0.26 μmol mg−1 min−1, respectively, on p-nitrophenyl N-acetyl-β-d-glucosaminide as substrate. The molecular mass of isozymes I and II was calculated to be 67 kDa by SDS–PAGE.
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| 2. |
- Hatzinikolaou, Dimitris G., et al.
(författare)
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Cell bound and extracellular glucose oxidases from Aspergillus niger BTL : evidence for a secondary glycosylation mechanism
- 2007
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Ingår i: Applied Biochemistry and Biotechnology. - : Springer Science and Business Media LLC. - 0273-2289 .- 1559-0291. ; 142:1, s. 29-43
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Tidskriftsartikel (refereegranskat)abstract
- Two glucose oxidase (GOX) isoforms where purified to electrophoretic homogeneity from the mycelium extract (GOXI) and the extracellular medium (GOXII) of Aspergillus niger BTL cultures. Both enzymes were found to be homodimers with nonreduced molecular masses of 148 and 159 kDa and pI values of 3.7 and 3.6 for GOXI and GOXII, respectively. The substrate specificity and the kinetic characteristics of the two GOX forms, as expressed through their apparent Km values on glucose, as well as pH and T activity optima, were almost identical. The only structural difference between the two enzymes was in their degrees of glycosylation, which were determined equal to 14.1 and 20.8% (w/w) of their molecular masses for GOXI and GOXII, respectively. The above difference in the carbohydrate content between the two enzymes seems to influence their pH and thermal stabilities. GOXII proved to be more stable than GOXI at pH values 2.5, 3.0, 8.0, and 9.0. Half-lives of GOXI at pH 3.0 and 8.0 were 8.9 and 17.5 h, respectively, whereas the corresponding values for GOXII were 13.5 and 28.1 h. As far as the thermal stability is concerned, GOXII was also more thermostable than GOXI as judged by the deactivation constants determined at various temperatures. More specifically, the half-lives of GOXI and GOXII, at 45°C, were 12 and 49 h, respectively. These results suggest A. niger BTL probably possesses a secondary glycosylation mechanism that increases the stability of the excreted GOX.
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| 3. |
- 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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| 4. |
- Kalantzi, Styliani, et al.
(författare)
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Effect of pectate lyase bioscouring on physical, chemical and low-stress mechanical properties of cotton fabrics
- 2008
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Ingår i: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 99:17, s. 8185-8192
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Tidskriftsartikel (refereegranskat)abstract
- The main objective of the present study was to meticulously investigate an inclusive set of physicochemical and handle properties (determined through Kawabata evaluation system) of bioscoured cotton fabrics. The application of a commercial pectinase preparation, Bioprep 3000L, for a range of concentrations and treatment times, could create a pectin-free textile with low wax content. Multiple regression analysis was used to describe the effect of enzymatic process variables on pectin and waxes removal.Comparison of fabrics’ properties such as wettability, whiteness, crystallinity index, and dyeing behaviour, confirmed that bioscouring could be as much effective as the conventional alkaline process. Uncovering the relationship between the composition of materials and their physicochemical properties was attempted. The application of higher enzyme concentrations generated fabrics with improved low-stress mechanical properties. Bending and shear rigidity, compressional resilience, as well as, extensibility of enzymatically treated cotton fabrics could be efficiently predicted by means of a single independent variable, the crystallinity index.
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| 5. |
- Kourtoglou, Elisavet, et al.
(författare)
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Constitutive expression, purification and characterization of a phosphoglucomutase from Fusarium oxysporum
- 2011
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Ingår i: Enzyme and microbial technology. - : Elsevier BV. - 0141-0229 .- 1879-0909. ; 48:3, s. 217-224
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Tidskriftsartikel (refereegranskat)abstract
- The phosphoglucomutase gene from a wild type Fusarium oxysporum strain (F3), was homologously expressed, under the control of the constitutive promoter of gpdA of Aspergillus nidulans. The transformant produced elevated levels of phosphoglucomutase activity compared to the wild type, a fact that facilitated the subsequent purification procedure. The enzyme (FoPGM) was purified to homogeneity applying three anion exchange and one gel filtration chromatography steps. The native enzyme revealed a monomeric structure with a molecular mass of 60 kDa, while the isoelectric point was 3.5. FoPGM was active in pH ranged from 6.0 to 8.0, with an optimum using 3-(N-morpholino)propanesulfonic acid buffer at 7.0, while loss of activity was observed when phosphate buffer was used in the above mentioned pH range. The optimal temperature for activity was 45 °C but the enzyme became unstable at temperatures above 40 °C. FoPGM requires the presence of a divalent cation for its function with maximum activity being obtained with Co2+. The apparent Km for Co2+ was found to be 10 μM. The enzyme was also active with other divalent metal ions such as Mn2+, Mg2+, Ni2+ and Ca2+ but to a lesser extent. The following kinetic constants were determined: vmax, 0.74 μmol mgprotein−1 min−1; kcat, 44.2 min−1; Km(G1P), 0.10 mM; Km(G1,6diP), 1.03 μM; kcat/Km(G1P), 443 mM−1 min−1 and kcat/Km(G1,6diP), 42,860 mM−1 min−1. The enzyme was considered to follow a Ping Pong substituted enzyme or enzyme isomerization mechanism.
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| 6. |
- Mamma, Diomi, et al.
(författare)
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Biochemical and catalytic properties of two intracellular β-glucosidases from the fungus Penicillium decumbens active on flavonoid glucosides
- 2004
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Ingår i: Journal of Molecular Catalysis B. - : Elsevier BV. - 1381-1177 .- 1873-3158. ; 27:4-6, s. 183-190
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Tidskriftsartikel (refereegranskat)abstract
- In the presence of rutin as sole carbon source, Penicillium decumbens produces two intracellular β-glucosidases named GI and GII, with molecular masses of 56,000 and 460,000 Da, respectively. The two proteins have been purified to homogeneity. GI and GII composed of two and four equal sub-units, respectively and displayed optimal activity at pH 7.0 and temperature 65–75 °C. Both β-glucosidases were competitively inhibited by glucose and glucono-δ-lactone. GI and GII exhibited broad substrate specificity, since they hydrolyzed a range of (1,3)-, (1,4)- and (1,6)-β-glucosides as well as aryl β-glucosides. Determination of kcat/Km revealed that GII hydrolyzed 3–8 times more efficiently the above-mentioned substrates. The ability of GI and GII to deglycosylate various flavonoid glycosides was also investigated. Both enzymes were active against flavonoids glycosylated at the 7 position but GII hydrolyzed them 5 times more efficiently than GI. Of the flavanols tested, both enzymes were incapable of hydrolyzing quercetrin and kaempferol-3-glucoside. The main difference between GI and GII as far as the hydrolysis of flavanols is concerned, was the ability of GII to hydrolyze the quercetin-3-glucoside.
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| 7. |
- Mamma, Diomi, et al.
(författare)
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Biochemical characterization of the multi-enzyme system produced by Penicillium decumbens grown on rutin
- 2004
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Ingår i: Food biotechnology. - 0890-5436 .- 1532-4249. ; 18:1, s. 1-18
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Tidskriftsartikel (refereegranskat)abstract
- Penicillium decumbens produced a set of enzymes, including a monoxygenase and two glycosidases, which degrade rutin, a nontoxic flavonoid glycoside, to water-soluble products. The monoxygenase (quercetinase) cleaves the heterocyclic ring in quercetin, the aglycone part of rutin. The glycosidases (alpha-L-rhamnosidase and beta-glucosidase) hydrolyze the bonds between quercetin and rutinose, and between glucose and rhamnose, the constituent monosaccharides of rutinose. Simultaneous production of the three enzymes was optimized following the examination of a number of culture conditions. Maximum enzyme activities were observed when the fungus was grown at 30 °C with an initial pH of 7.0, using 8.0 g/L rutin and 9.0 g/L di-ammonium hydrogen phosphate as carbon and nitrogen sources, respectively. The enzymes were purified to electrophoretic homogeneity by a series of consecutive chromatographic steps including anion and cation exchange as well as gel filtration. The purified quercetinase revealed an apparent tetrameric structure, with a reduced molecular mass of 45 kDa. alpha-L-Rhamnosidase showed an apparent molecular mass of 58 kDa and the purified beta-glucosidase was a tetramer exhibiting a reduced molecular mass of 120 kDa.
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| 8. |
- Mamma, Diomi, et al.
(författare)
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Biodegradation of phenol by acclimatized Pseudomonas putida cells using glucose as an added growth substrate
- 2004
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Ingår i: Journal of Environmental Science and Health. Part A. - 1093-4529 .- 1532-4117. ; 39:8, s. 2093-2104
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Tidskriftsartikel (refereegranskat)abstract
- Biodegradation of phenol, a pollutant derived from many industrial processes, was achieved through acclimatized Pseudomonas putida cells. The strategy to overcome the inhibitory effect of phenol on microbial growth involved the addition of glucose, a conventional carbon source. A factorial experimental design was employed in order to optimize the initial phenol and glucose concentrations. The optimum conditions found were applied in 2-lt bioreactors. The development of acclimatized cells and the use of glucose as an added growth substrate resulted in a significant phenol degradation rate of 60.7 mg L−1 h−1 with a complete removal of 1200 mg L−1 phenol.
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| 9. |
- Mamma, Diomi, et al.
(författare)
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Biotechnological potential of fruit processing industry residues
- 2009
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Ingår i: Biotechnology for Agro-Industrial Residues Utilisation. - Dordrecht : Encyclopedia of Global Archaeology/Springer Verlag. - 9781402099410 - 9781402099427 ; , s. 273-291
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Bokkapitel (refereegranskat)abstract
- Fruit juices and derived products such as nectars and drinks have experienced growing popularity within the last years. Orange waste, apple pomace and grape pomace are the solid by-products derived from processing of oranges, apples and grapes, respectively. Due to increasing production, their disposal represents a growing problem since the plant material is usually prone to microbial spoilage, thus limiting further exploitation. On the other hand, costs of drying, storage and shipment of by-products are economically limiting factors. Therefore, agro-industrial by-products are often utilized as feed or as fertilizer. The application of agro-industrial 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 orange waste, apple pomace and grape pomace to generate several value-added products through microbial transformations or enzymatic modifications, such as enzymes, bioethanol, organic acids, heteropolysaccharides, aroma compounds, protein enriched feeds, prebiotic oligosaccharides and biologically active molecules
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| 10. |
- Mamma, Diomi, et al.
(författare)
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Citrus peels : a potential feedstock for bioethanol production
- 2008
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Ingår i: Tree and Forestry Science and Biotechnology. - 1752-3753. ; 2:1, s. 135-140
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Tidskriftsartikel (refereegranskat)abstract
- Orange peels (OPs) and water unextractable orange peels (WUOPs) were evaluated as feedstocks for bioethanol production, applying simultaneous saccharification and co-fermentation (SSCF). Τhe fungi, Fusarium oxysporum F3 and Neurospora crassa DSM 1129, were grown aerobically under solid state cultivation (SSC) in order to produce the necessary enzymes for hydrolyzing the polysaccharides present in OPs. Following aerated growth and production of hydrolytic enzymes, OPs and WUOPs were fermented to bioethanol. Factors affecting bioethanol production such as, OP and WUOP concentration and the use of single fungal or mixed culture with S. cerevisiae, were investigated. Both microorganisms were capable of producing bioethanol in single or mixed cultures with S. cerevisiae. F. oxysporum F3 was a better ethanol producer than N. crassa in single or mixed cultures. Yields as high as 23 g of ethanol/100 g of added OPs and 19.98 g of ethanol/100 g of added WUOPs corresponding to 65% and 74%, respectively, of the theoretical yield based on total carbohydrate content of OPs or WUOPs, were achieved with F. oxysporum F3.
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| 11. |
- Mamma, Diomi, et al.
(författare)
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Effect of adsorption characteristics of a modified cellulase on indigo backstaining
- 2004
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Ingår i: Journal of chemical technology and biotechnology (1986). - : Wiley. - 0268-2575 .- 1097-4660. ; 79:6, s. 639-644
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Tidskriftsartikel (refereegranskat)abstract
- The effect of limited proteolysis (digestion) of a commercial cellulase preparation (Ecostone((R)) L350) on backstaining with indigo was investigated. The influence of protease (papain) concentration on limited proteolysis of cellulase preparation was studied, applying different ratios of papain/cellulase (w/w). Changes in adsorption on Avicel cellulose of the non-digested compared with the papain-digested Ecostone((R)) L350 were examined using the Langmuir adsorption isotherm. The non-digested Ecostone((R)) L350 exhibited stronger interaction to Avicel cellulose compared with the digested form, while the maximum efficiency of cellulase adsorption to Avicel cellulose decreased after digestion. When papain-digested Ecostone((R)) L350 was applied on cotton fabrics during the dyeing procedure with indigo, a reduction of indigo backstaining was obtained compared with the non-digested Ecostone((R)) L350.
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| 12. |
- Mamma, Diomi, et al.
(författare)
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Fungal multienzyme production on industrial by-products of the citrus-processing industry
- 2008
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Ingår i: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 99:7, s. 2373-2383
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Tidskriftsartikel (refereegranskat)abstract
- Orange peels is the principal solid by-product of the citrus processing industry and the disposal of the fresh peels is becoming a major problem to many factories. Dry citrus peels are rich in pectin, cellulose and hemicellulose and may be used as a fermentation substrate. Production of multienzyme preparations containing pectinolytic, cellulolytic and xylanolytic enzymes by the mesophilic fungi Aspergillus niger BTL, Fusarium oxysporum F3, Neurospora crassa DSM 1129 and Penicillium decumbens under solid-state fermentation (SSF) on dry orange peels was enhanced by optimization of initial pH of the culture medium and initial moisture level. Under optimal conditions A. niger BTL was by far the most potent strain in polygalacturonase and pectate lyase, production followed by F. oxysporum F3, N. crassa DSM 1129 and P. decumbens. N. crassa DSM 1129 produced the highest endoglucanase activity and P. decumbens the lowest one. Comparison of xylanase production revealed that A. niger BTL produced the highest activity followed by N. crassa DSM 1129, P. decumbens and F. oxysporum F3. N. crassa DSM 1129 and P. decumbens did not produce any β-xylosidase activity, while A. niger BTL produced approximately 10 times more β-xylosidase than F. oxysporum F3. The highest invertase activity was produced by A. niger BTL while the lowest ones by F. oxysporum F3 and P. decumbens. After SSF of the four fungi, under optimal conditions, the fermented substrate was either directly exposed to autohydrolysis or new material was added, and the in situ produced multienzyme systems were successfully used for the partial degradation of orange peels polysaccharides and the liberation of fermentable sugars.
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| 13. |
- Mamma, Diomi, et al.
(författare)
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Removal of 1,3-dichloro2-propanol and 3-chloro-1,2-propanediol by the whole cell system of Pseudomonas putida DSM 437
- 2006
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Ingår i: Journal of Environmental Science and Health. Part A. - : Informa UK Limited. - 1093-4529 .- 1532-4117. ; 41:3, s. 303-313
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Tidskriftsartikel (refereegranskat)abstract
- The removal of 1,3-dichloro-2-propanol (1,3-DCP), 3-chloro-1,2-propanediol (3-CPD) and their mixtures at concentrations up to 1000 mg · L−1 by the whole cell system of Pseudomonas putida DSM 437 was investigated. The 1,3-DCP removal rates ranged from 2.36 to 10.55 mg · L−1 · h−1; 3-CPD exhibited approximately two times higher removal rates compared to 1,3-DCP for all concentrations tested. Removal of 1,3-DCP and 3-CPD followed first-order kinetics with rate constants of 0.0109 h−1 and 0.0206 h−1, respectively. When the whole cell system of P. putida DSM 437 was applied to mixtures of the two halohdrins, complete removal of 1,3-DCP was achieved at 144 h while removal of 3-CPD was completed at times ranging from 72 to 144 h. Time to achieve 50% removal of both halohydrins depends on the initial concentration of each in the mixture. For 1,3-DCP, it ranged from 40.55 h at 200 mg · L−1 to 53.28 h at 500 mg · L−1 while the respected values for 3-CPD were 33.39 and 68.91 h.
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