| 1. |
- 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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| 2. |
- 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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| 3. |
- 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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| 4. |
- 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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| 5. |
- 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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| 6. |
- 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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| 7. |
- 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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| 8. |
- Shuoker, Bashar, et al.
(författare)
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Sialidases and fucosidases of Akkermansia muciniphila are crucial for growth on mucin and nutrient sharing with mucus-associated gut bacteria
- 2023
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Ingår i: Nature Communications. - 2041-1723. ; 14
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Tidskriftsartikel (refereegranskat)abstract
- The mucolytic human gut microbiota specialist Akkermansia muciniphila is proposed to boost mucin-secretion by the host, thereby being a key player in mucus turnover. Mucin glycan utilization requires the removal of protective caps, notably fucose and sialic acid, but the enzymatic details of this process remain largely unknown. Here, we describe the specificities of ten A. muciniphila glycoside hydrolases, which collectively remove all known sialyl and fucosyl mucin caps including those on double-sulfated epitopes. Structural analyses revealed an unprecedented fucosidase modular arrangement and explained the sialyl T-antigen specificity of a sialidase of a previously unknown family. Cell-attached sialidases and fucosidases displayed mucin-binding and their inhibition abolished growth of A. muciniphila on mucin. Remarkably, neither the sialic acid nor fucose contributed to A. muciniphila growth, but instead promoted butyrate production by co-cultured Clostridia. This study brings unprecedented mechanistic insight into the initiation of mucin O-glycan degradation by A. muciniphila and nutrient sharing between mucus-associated bacteria.
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| 9. |
- Aevarsson, Arnthór, et al.
(författare)
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Going to extremes - a metagenomic journey into the dark matter of life
- 2021
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Ingår i: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 1574-6968. ; 368:12
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Forskningsöversikt (refereegranskat)abstract
- The Virus-X-Viral Metagenomics for Innovation Value-project was a scientific expedition to explore and exploit uncharted territory of genetic diversity in extreme natural environments such as geothermal hot springs and deep-sea ocean ecosystems. Specifically, the project was set to analyse and exploit viral metagenomes with the ultimate goal of developing new gene products with high innovation value for applications in biotechnology, pharmaceutical, medical, and the life science sectors. Viral gene pool analysis is also essential to obtain fundamental insight into ecosystem dynamics and to investigate how viruses influence the evolution of microbes and multicellular organisms. The Virus-X Consortium, established in 2016, included experts from eight European countries. The unique approach based on high throughput bioinformatics technologies combined with structural and functional studies resulted in the development of a biodiscovery pipeline of significant capacity and scale. The activities within the Virus-X consortium cover the entire range from bioprospecting and methods development in bioinformatics to protein production and characterisation, with the final goal of translating our results into new products for the bioeconomy. The significant impact the consortium made in all of these areas was possible due to the successful cooperation between expert teams that worked together to solve a complex scientific problem using state-of-the-art technologies as well as developing novel tools to explore the virosphere, widely considered as the last great frontier of life.
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| 10. |
- Ahlqvist, Josefin, et al.
(författare)
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Crystal structure and initial characterization of a novel archaeal-like Holliday junction-resolving enzyme from Thermus thermophilus phage Tth15-6
- 2022
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Ingår i: Acta crystallographica. Section D, Structural biology. - 2059-7983. ; 78:Pt 2, s. 212-227
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Tidskriftsartikel (refereegranskat)abstract
- This study describes the production, characterization and structure determination of a novel Holliday junction-resolving enzyme. The enzyme, termed Hjc_15-6, is encoded in the genome of phage Tth15-6, which infects Thermus thermophilus. Hjc_15-6 was heterologously produced in Escherichia coli and high yields of soluble and biologically active recombinant enzyme were obtained in both complex and defined media. Amino-acid sequence and structure comparison suggested that the enzyme belongs to a group of enzymes classified as archaeal Holliday junction-resolving enzymes, which are typically divalent metal ion-binding dimers that are able to cleave X-shaped dsDNA-Holliday junctions (Hjs). The crystal structure of Hjc_15-6 was determined to 2.5 Å resolution using the selenomethionine single-wavelength anomalous dispersion method. To our knowledge, this is the first crystal structure of an Hj-resolving enzyme originating from a bacteriophage that can be classified as an archaeal type of Hj-resolving enzyme. As such, it represents a new fold for Hj-resolving enzymes from phages. Characterization of the structure of Hjc_15-6 suggests that it may form a dimer, or even a homodimer of dimers, and activity studies show endonuclease activity towards Hjs. Furthermore, based on sequence analysis it is proposed that Hjc_15-6 has a three-part catalytic motif corresponding to E-SD-EVK, and this motif may be common among other Hj-resolving enzymes originating from thermophilic bacteriophages.
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