| 1. |
- Abou Hachem, Maher, et al.
(författare)
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Carbohydrate-binding modules from a thermostable Rhodothermus marinus xylanase : Cloning, expression and binding studies
- 2000
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Ingår i: Biochemical Journal. - : Portland Press Ltd.. - 0264-6021. ; 345:1, s. 53-60
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Tidskriftsartikel (refereegranskat)abstract
- The two N-terminally repeated carbohydrate-binding modules (CBM4-1 and CBM4-2) encoded by xyn10A from Rhodothermus marinus were produced in Escherichia coli and purified by affinity chromatography. Binding assays to insoluble polysaccharides showed binding to insoluble xylan and to phosphoric-acid-swollen cellulose but not to Avicel or crystalline cellulose. Binding to insoluble substrates was significantly enhanced by the presence of Na+ and Ca2+ ions. The binding affinities for soluble polysaccharides were tested by affinity electrophoresis; strong binding occurred with different xylans and β-glucan. CBM4-2 displayed a somewhat higher binding affinity than CBM4-1 for both soluble and insoluble substrates but both had similar specificities. Binding to short oligosaccharides was measured by NMR; both modules bound with similar affinities. The binding of the modules was shown to be dominated by enthalpic forces. The binding modules did not contribute with any significant synergistic effects on xylan hydrolysis when incubated with a Xyn10A catalytic module. This is the first report of family 4 CBMs with affinity for both insoluble xylan and amorphous cellulose.
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| 2. |
- Karlsson, Eva Nordberg, et al.
(författare)
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Cloning and sequence of a thermostable multidomain xylanase from the bacterium Rhodothermus marinus
- 1997
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Ingår i: Biochimica et Biophysica Acta - Gene Structure and Expression. - 0167-4781. ; 1353:2, s. 118-124
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Tidskriftsartikel (refereegranskat)abstract
- The gene (xyn1) encoding a Rhodothermus marinus xylanase has been cloned and expressed in Escherichia coli. The gene comprises 5 different domains in an unusual combination. The cellulose binding domains (CBDs) encoded by xyn1 are repeated in tandem at the N-terminus and show similarity with the CBD family IV. The xyn1-gene is the first example encoding a CBD family IV in combination with a xylan hydrolyzing catalytic domain of the glycosyl hydrolase family 10.
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| 3. |
- Nordberg Karlsson, Eva, et al.
(författare)
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Evidence for substrate binding of a recombinant thermostable xylanase originating from Rhodothermus marinus
- 1998
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Ingår i: FEMS Microbiology Letters. - 0378-1097. ; 168:1, s. 1-7
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Tidskriftsartikel (refereegranskat)abstract
- The xyn1 encoded 5 domain xylanase from the thermophilic bacterium Rhodothermus marinus binds specifically to xylan, β-glucan and amorphous but not crystalline cellulose. Our results show that the binding is mediated by the full length xylanase, but not by the catalytic domain only. Based on similarities concerning both predicted secondary structure and binding specificity found with one cellulose binding domain of CenC from Cellulomonas fimi, we suggest that the binding is mediated by the two N-terminally repeated domains. Copyright (C) 1998 Federation of European Microbiological Societies.
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| 4. |
- Salomonsson, Emma, et al.
(författare)
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Mutational tuning of galectin-3 specificity and biological function.
- 2010
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Ingår i: The Journal of biological chemistry. - 1083-351X. ; 285, s. 35079-35091
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Tidskriftsartikel (refereegranskat)abstract
- Galectins are defined by a conserved beta-galactoside binding site, which has been linked to many of their important functions in e.g. cell adhesion, signaling and intracellular trafficking. Weak adjacent sites may enhance or decrease affinity for natural beta-galactoside containing glycoconjugates, but little is known about the biological role of this modulation of affinity (fine specificity). We have now produced 10 mutants of human galectin-3, with changes in these adjacent sites, which have altered carbohydrate-binding fine specificity but which retain the basic beta-galactoside binding activity as show by glycan-array binding and a solution-based fluorescence anisotropy assay. Each mutant was also tested in two biological assays to provide a correlation between fine specificity and function. Galectin-3 R186S, which has selectively lost affinity for LacNAc, a disaccharide moiety commonly found on glycoprotein glycans, has lost the ability to activate neutrophil leukocytes and intracellular targeting into vesicles. K176L has increased affinity for beta-galactosides substituted with GlcNAcbeta1-3 as found in poly-N-acetyllactosaminoglycans, and increased potency to activate neutrophil leukocytes, even though it has lost other aspects of galectin-3 fine specificity. G182A has altered carbohydrate-binding fine specificity and altered intracellular targeting into vesicles, a possible link to the intracellular galectin-3-mediated anti-apoptotic effect known to be lost by this mutant. Finally, the mutants have helped to define the differences in fine specificity shown by Xenopus, mouse and human galectin-3 and as such, evidence for adaptive change during evolution.
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| 5. |
- Schmitz, Eva, et al.
(författare)
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Altering the water holding capacity of potato pulp via structural modifications of the pectic polysaccharides
- 2021
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Ingår i: Carbohydrate Polymer Technologies and Applications. - : Elsevier BV. - 2666-8939. ; 2
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Tidskriftsartikel (refereegranskat)abstract
- Potato pulp is a low value agricultural side stream with great valorisation potential as prebiotic food ingredient. An interesting functionality different from other prebiotics is its high water holding capacity (WHC). This study aims at exploring the relationship between physical and enzymatic modifications in the potato pulp and its WHC. Different temperature treatments and storage conditions were found to have a great influence on the WHC, freezing decreasing the WHC the least (15%) compared to fresh pulp. Ultrasonication of frozen pulp increased its WHC by 32%, while it did not have an effect on fresh pulp. Of the various tested enzymes, only protease led to an increase in WHC of fresh pulp (by 48%). The WHC of frozen and dry pulp could not be positively influenced by enzymatic treatment. Structurally, the potato pulps with increased WHC exhibited a larger surface area and more flaky structure.
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| 6. |
- Schmitz, Eva, et al.
(författare)
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Chemical and biochemical bleaching of oat hulls : The effect of hydrogen peroxide, laccase, xylanase and sonication on optical properties and chemical composition
- 2021
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Ingår i: Biotechnology Reports. - : Elsevier BV. - 2215-017X. ; 30
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Tidskriftsartikel (refereegranskat)abstract
- Oat hulls are an excellent dietary fibre source for food supplements due to their rich lignocellulose composition as well as their great abundance as low-value agricultural side stream. For the production of white fibre supplements, a mild, but effective bleaching of the hulls is required. Chemical bleaching with hydrogen peroxide and sodium hydroxide was here found to be a suitable method increasing the CIE L* value (corresponds to a lightness value) above 85. The developed method is mild, retaining the hull's chemical composition. Only a minor decrease in coniferaldehyde structures upon bleaching was detected. Colour and chemical variabilities of oat hulls from different growth seasons did not influence the required bleaching conditions to achieve the desired optical properties. The inclusion of biochemical bleaching steps utilizing the xylanase Pentopan Mono BG, the laccase NS51003 and sonication was industrially not feasible as they could not reduce the required amount of subsequently applied bleaching chemicals significantly.
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| 7. |
- Schmitz, Eva, et al.
(författare)
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Lignocellulose degradation for the bioeconomy: The potential of enzyme synergies between xylanases, ferulic acid esterase and laccase for the production of arabinoxylo-oligosaccharides
- 2022
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Ingår i: Bioresource Technology. - : Elsevier BV. - 0960-8524. ; 343
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Tidskriftsartikel (refereegranskat)abstract
- The success of establishing bioeconomies replacing current economies based on fossil resources largely depends on our ability to degrade recalcitrant lignocellulosic biomass. This study explores the potential of employing various enzymes acting synergistically on previously pretreated agricultural side streams (corn bran, oat hull, soluble and insoluble oat bran). Degrees of synergy (oligosaccharide yield obtained with the enzyme combination divided by the sum of yields obtained with individual enzymes) of up to 88 were obtained. Combinations of a ferulic acid esterase and xylanases resulted in synergy on all substrates, while a laccase and xylanases only acted synergistically on the more recalcitrant substrates. Synergy between different xylanases (glycoside hydrolase (GH) families 5 and 11) was observed particularly on oat hulls, producing a yield of 57%. The synergistic ability of the enzymes was found to be partly due to the increased enzyme stability when in combination with the substrates.
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| 8. |
- Schmitz, Eva, et al.
(författare)
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Novel Function of CtXyn5A from Acetivibrio thermocellus : Dual Arabinoxylanase and Feruloyl Esterase Activity in the Same Active Site
- 2023
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Ingår i: ChemBioChem. - : Wiley. - 1439-4227 .- 1439-7633. ; 24:3
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Tidskriftsartikel (refereegranskat)abstract
- Uncharacterized side activities of enzymes can have significant effects on reaction products and yields. Hence, their identification and characterization are crucial for the development of successful reaction systems. Here, we report the presence of feruloyl esterase activity in CtXyn5A from Acetivibrio thermocellus, besides its well-known arabinoxylanase activity, for the first time. Activity analysis of enzyme variants mutated in the catalytic nucleophile, Glu279, confirmed removal of all activity for E279A and E279L, and increased esterase activity while removing xylanase activity for E279S, allowing the proposal that both reaction types are catalysed in the same active site in two subsequential steps. The ferulic acid substituent is cleaved off first, followed by hydrolysis of the xylan backbone. The esterase activity on complex carbohydrates was found to be higher than the one of a designated ferulic acid esterase (E-FAERU). Therefore, we conclude that the enzyme exhibits a dual function rather than an esterase side activity.
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| 9. |
- Schmitz, Eva, et al.
(författare)
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Ultrasound Assisted Alkaline Pre‐treatment Efficiently Solubilises Hemicellulose from Oat Hulls
- 2021
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Ingår i: Waste and Biomass Valorization. - : Springer Science and Business Media LLC. - 1877-2641 .- 1877-265X. ; 12:10, s. 5371-5381
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Tidskriftsartikel (refereegranskat)abstract
- The establishment of sustainable bioeconomies requires the utilization of new renewable biomaterials. One such material currently seen as a waste product is oat hulls. Oat hulls exhibit a great potential for the production of dietary fibres due to their exceptionally large hemicellulose content (35%). Their recalcitrant structure however requires a suitable pre-treatment method to access and process the hemicellulose. After a screening of various physical, chemical and physico-chemical pre-treatment methods, including autoclaving, ultrasonication, microwave-, deep eutectic solvents-, as well as alkaline treatments, a combined ultrasonication and alkali pre-treatment method was here found to be the most suitable. A factorial design resulted in optimized conditions of 10 min ultrasonication in water, followed by an incubation in 5 M NaOH at 80 ºC for 9 h yielding solubilisation of 72% of all hemicellulose in the hulls. The method was shown to efficiently break the ester bonds between ferulic acid and the hemicellulose main chain, contributing to its solubilisation. Graphic Abstract: [Figure not available: see fulltext.]
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| 10. |
- Schmitz, Eva, et al.
(författare)
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Warming weathers changes the chemical composition of oat hulls
- 2020
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Ingår i: Plant Biology. - : Wiley. - 1438-8677 .- 1435-8603. ; 22:6, s. 1086-1091
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Tidskriftsartikel (refereegranskat)abstract
- The current threats of climate change are driving attention away from the petrochemical industry towards more sustainable and bio‐based production processes for fuels and speciality chemicals. These processes require suitable low‐cost starting material. One potential material assessed here is the oat hull. Its overall chemical composition has so far not been fully characterized. Furthermore, it is not known how it is affected by extreme weather events.Oat hulls (Kerstin and Galant varieties) grown during ‘normal’ weather years (2016 and 2017) are compared to the harvest of the warmer and drier year (2018). Standard methods for determination of plant chemical composition, with focus on carbohydrate composition, are utilized.Oat hulls grown in ‘normal’ weather conditions (2017) are rich in lignocellulose (84%), consisting of 35% hemicellulose, 25% lignin and 23% cellulose. Arabinoxylan was found to be the major biopolymer (32%). However, this composition is greatly influenced by weather variations during the oat growth phase. A lignocellulose reduction of 25% was recorded in the warmer and drier 2018 harvest. Additionally, a 6.6‐fold increase in starch content, a four‐fold increase in protein content and a 60% decrease in phenolic content was noted.Due to its high lignocellulose composition, with an exceptionally large hemicellulose fraction, the chemical composition of oat hulls is unique among agricultural by‐products. However, this characteristic is significantly reduced when grown in warmer and drier weather, which could compromise its suitability for use in a successful biorefinery.
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