| 1. |
- Nordberg Karlsson, Eva, et al.
(författare)
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Endo-xylanases as tools for production of substituted xylooligosaccharides with prebiotic properties
- 2018
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Ingår i: Applied Microbiology and Biotechnology. - : Springer Science and Business Media LLC. - 0175-7598 .- 1432-0614. ; 102:21, s. 9081-9088
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Forskningsöversikt (refereegranskat)abstract
- Xylan has a main chain consisting of β-1,4-linked xylose residues with diverse substituents. Endoxylanases cleave the xylan chain at cleavage sites determined by the substitution pattern and thus give different oligosaccharide product patterns. Most known endoxylanases belong to glycoside hydrolase (GH) families 10 and 11. These enzymes work well on unsubstituted xylan but accept substituents in certain subsites. The GH11 enzymes are more restricted by substituents, but on the other hand, they are normally more active than the GH10 enzymes on insoluble substrates, because of their smaller size. GH5 endoxylanases accept arabinose substituents in several subsites and require it in the − 1 subsite. This specificity makes the GH5 endoxylanases very useful for degradation of highly arabinose-substituted xylans and for the selective production of arabinoxylooligosaccharides, without formation of unsubstituted xylooligosaccharides. The GH30 endoxylanases have a related type of specificity in that they require a uronic acid substituent in the − 2 subsite, which makes them very useful for the production of uronic acid substituted oligosaccharides. The ability of dietary xylooligosaccharides to function as prebiotics in humans is governed by their substitution patterns. Endoxylanases are thus excellent tools to tailor prebiotic oligosaccharides to stimulate various types of intestinal bacteria and to cause fermentation in different parts of the gastrointestinal tract. Continuously increasing knowledge on the function of the gut microbiota and discoveries of novel endoxylanases increase the possibilities to achieve health-promoting effects.
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| 2. |
- 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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| 3. |
- Schmitz, Eva, et al.
(författare)
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Novel Function of CtXyn5A from Acetivibrio thermocellus: Dual Arabinoxylanase and Feruloyl Esterase Activity Occur in the Same Active Site
- 2022
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Uncharacterized side activities of enzymes can have significant negative effects on reaction products and yields. Hence, their identification and characterization is 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. Both reaction types appear to be catalysed in the same active site in two subsequential steps. The ferulic acid substituent is cleaved off first, followed by the 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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| 4. |
- 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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| 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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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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| 9. |
- de Maré, Lena, et al.
(författare)
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A cultivation technique for E. coli fed-batch cultivations operating close to the maximum oxygen transfer capacity of the reactor
- 2005
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Ingår i: Biotechnology Letters. - : Springer Science and Business Media LLC. - 0141-5492 .- 1573-6776. ; 27:14, s. 983-990
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Tidskriftsartikel (refereegranskat)abstract
- A cultivation strategy combining the advantages of temperature-limited fed-batch and probing feeding control is presented. The technique was evaluated in fed-batch cultivations with E. coli BL21(DE3) producing xylanase in a 3 liter bioreactor. A 20% increase in cell mass was achieved and the usual decrease in specific enzyme activity normally observed during the late production phase was diminished with the new technique. The method was further tested by growing E. coli W3110 in a larger bioreactor (50 l). It is a suitable cultivation technique when the O2 transfer capacity of the reactor is reached and it is desired to continue to produce the recombinant protein.
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| 10. |
- Cabero, Karen, et al.
(författare)
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A cellulolytic Hypocrea strain isolated from South American brave straw produces a modular xylanase.
- 2012
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Ingår i: Carbohydrate Research. - : Elsevier BV. - 1873-426X .- 0008-6215. ; 356, s. 215-223
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Tidskriftsartikel (refereegranskat)abstract
- Cellulase-producing fungi from the Andean regions in Bolivia, an ecosystem characterized as an extreme arid highland, were studied. Thirty-two isolates were screened for presence of cellulase activity using carboxymethyl cellulose (CMC) as carbon source, and activity was confirmed using a filter paper assay. One isolate, denoted as BLT1C was selected from this screening, and sequence analysis of the internal transcribed spacer (ITS) classified the strain as Hypocrea lixii. The secretome of BLT1C showed high xylanase activity (compared to that of two reference Trichoderma reesei strains) when cultivated using brave straw, an abundant native grass from the area, as carbon source. SDS-PAGE analysis revealed three main protein-bands (18, 32 and 65kDa) and in-gel digestion and mass spectrometry combined with activity analysis showed that these proteins were active xylanases with molecular masses corresponding to (I) a single glycoside hydrolase family 11 catalytic module (18kDa), and (II, III) modular enzymes, with the GH11 catalytic domain connected to a module of unknown function (32kDa) or putatively connected to a GH7 catalytic module (65kDa). The N-terminal sequence of the 65kDa xylanase did not show significant sequence similarities to deposited sequences. The collected data on xylanase activity, molecular mass, GH11-sequence conservation, combined with lack of sequence similarities in the N-terminus show that the 65kDa band corresponds to a novel modular xylanase.
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