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| 2. |
- Höije, Anders, 1980, et al.
(författare)
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Material properties of films from enzymatically tailored arabinoxylans
- 2008
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Ingår i: Biomacromolecules. - 1525-7797 .- 1526-4602. ; :9, s. 2042-2047
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Tidskriftsartikel (refereegranskat)abstract
- Rye arabinoxylan with an initial arabinose to xylose (Ara/Xyl) ratio of 0.50 was enzymatically modified with α-L-arabinofuranosidase. Different enzyme dosages were used to prepare arabinoxylan samples with a gradient of arabinose content varying from Ara/Xyl ratio 0.50 to 0.20. The degree of polymerization of the arabinoxylans was not affected by the enzymatic treatment, as detected with SEC-MALLS. Arabinoxylan samples with an Ara/Xyl ratio of 0.30 and below agglomerated in a water solution as seen by changes in light scattering. All samples, however, formed cohesive films upon drying, without addition of external plasticisers. The film from untreated arabinoxylan was completely amorphous; whereas films of the enzyme treated arabinoxylans were semi-crystalline with an increasing degree of crystallinity with decreasing arabinose content as determined by WAXS. Oxygen permeability measurements of the films showed that decreased arabinose content also resulted in lower oxygen permeability of the films. All films were strong and relatively stiff, but showed variations in strain at break. The moderately debranched film with an Ara/Xyl ratio of 0.37 had highest strain at break among all the films tested, yet was stiff and strong. This material also exhibited yielding, and had stress/strain behavior similar to synthetic semi-crystalline polymers, with a tendency to strain induced crystallization. Such combination of mechanical properties combined with oxygen barrier properties is very attractive for packaging applications.
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| 3. |
- Mikkonen, Krisi S., et al.
(författare)
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Mannan-cellulose nanocomposites
- 2008
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Ingår i: Abstracts of Papers of the American Chemical Society. - 0065-7727. ; 235:228
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 4. |
- Puchar, Vladimir, et al.
(författare)
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Substrate and positional specificity of feruloyl esterases for monoferuloylated and monoacetylated 4-nitrophenyl glycosides
- 2007
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Ingår i: Journal of Biotechnology. - : Elsevier BV. - 0168-1656 .- 1873-4863. ; 127:2, s. 235-243
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Tidskriftsartikel (refereegranskat)abstract
- 4-Nitrophenyl glycosides of 2-, 3-, and 5-O-(E)-feruloyl- and 2- and 5-O-acetyl-α-l-arabinofuranosides and of 2-, 3-, and 4-O-(E)-feruloyl- and 2-, 3- and 4-O-acetyl-β-d-xylopyranosides, compounds mimicking natural substrates, were used to investigate substrate and positional specificity of type-A, -B, and -C feruloyl esterases. All the feruloyl esterases behave as true feruloyl esterases showing negligible activity on sugar acetates. Type-A enzymes, represented by AnFaeA from Aspergillus niger and FoFaeII from Fusarium oxysporum, are specialized for deferuloylation of primary hydroxyl groups, with a very strong preference for hydrolyzing 5-O-feruloyl-α-l-arabinofuranoside. On the contrary, type-B and -C feruloyl esterases, represented by FoFaeI from F. oxysporum and TsFaeC from Talaromyces stipitatus, acted on almost all ferulates with exception of 4- and 3-O-feruloyl-β-d-xylopyranoside. 5-O-Feruloyl-α-l-arabinofuranoside was the best substrate for both TsFaeC and FoFaeI, although catalytic efficiency of the latter enzyme toward 2-O-feruloyl-α-l-arabinofuranoside was comparable. In comparison with acetates, the corresponding ferulates served as poor substrates for the carbohydrate esterase family 1 feruloyl esterase from Aspergillus oryzae. The enzyme hydrolyzed all α-l-arabinofuranoside and β-d-xylopyranoside acetates. It behaved as a non-specific acetyl esterase rather than a feruloyl esterase, with a preference for 2-O-acetyl-β-d-xylopyranoside.
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