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Composition and structure of cell wall ulvans recovered from Ulva spp. along the Swedish west coast
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
Chalmers Univ Technol, Chem & Chem Engn Organ Chem, SE-41296 Gothenburg, Sweden..
Chalmers Univ Technol, Biol & Biol Engn Ind Biotechnol, SE-41296 Gothenburg, Sweden..
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2020 (English)In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 233, article id 115852Article in journal (Refereed) Published
Abstract [en]

The cell wall polysaccharide ulvan was isolated from two species of the seaweed Ulva collected along the Swedish west coast. Acidic extraction was benchmarked against hot water extraction with enzymatic purification and against commercial ulvan. Extracted ulvan contained 11-18 % g/g of ash, some protein (up to 1.3 % g N/g) but minimal colored impurities. The ulvans had high molecular weights (660,000-760,000 g/mol) and were composed of 77-79 % g/g carbohydrates, mainly rhamnose, xylose, glucose, glucuronic acid, and iduronic acid. The extraction protocol and the ulvan source strongly impact the molecular weight and the chemical composition. Acidic extraction caused almost complete desulfation of the isolated ulvan while the other method preserved a significant degree of SO3 substituents. Elemental analysis of ash remaining after thermal degradation showed presence of common mineral elements such as Na, Ca, Mg, Al, and K, but none of the heavy metals Pb, Hg, or As.

Place, publisher, year, edition, pages
ELSEVIER SCI LTD , 2020. Vol. 233, article id 115852
Keywords [en]
Ulva spp., Ulvan, Extraction, Composition, Sulfation, Structure
National Category
Basic Medicine
Identifiers
URN: urn:nbn:se:kth:diva-269441DOI: 10.1016/j.carbpol.2020.115852ISI: 000513914400029PubMedID: 32059903Scopus ID: 2-s2.0-85077645228OAI: oai:DiVA.org:kth-269441DiVA, id: diva2:1414771
Note

QC 20200316

Available from: 2020-03-16 Created: 2020-03-16 Last updated: 2020-05-04Bibliographically approved
In thesis
1. Polysaccharides from red and green seaweed: Extraction, characterisation and applications
Open this publication in new window or tab >>Polysaccharides from red and green seaweed: Extraction, characterisation and applications
2020 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Cultivation of seaweed has been conducted for centuries in Asia, but is largely undeveloped in Sweden even though there is potential for this industry. Seaweed offers benefits compared with land-based biomass cultivation. Cultivation of seaweed does not occupy land areas and does not require irrigation or fertilizers, which contributes to avoid coastal eutrophication. Seaweed contains polysaccharides and is a potential feedstock for production of bio-based materials. The aim of this thesis was to extract and map the chemical structure of polysaccharides from macroalgae collected along the Swedish west coast. Another aim was to use the extracted polysaccharides to design new bio-based materials. In the first study, a fractionation strategy was developed to sequentially extract proteins and polysaccharides from the red macroalgae Porphyra. The fractionation yielded one protein fraction and three polysaccharide fractions. In the second study, the polysaccharide ulvan was extracted from two species of the green macroalgae Ulva. Two different extraction protocols were tested. Parameters such as the yield, molecular weight and monosaccharide composition of the extracted ulvan depended on the extraction protocol and the specie of Ulva used for the extraction. In the third study, ulvan extracted from Ulva was used to prepare hydrogels, which were tested as an adsorbent for heavy metals and the dye methylene blue. Ulvan was first oxidized into ulvan dialdehyde and mixed with gelatin, yielding hydrogels. The hydrogels showed high water-uptake capacity and a high adsorption capacity of methylene blue. The hydrogels also adsorbed heavy metal ions. In the fourth study, cellulose was extracted from Ulva and further used to prepare cellulose nanofibrils (CNF). Chemical analysis of the CNF showed that it contains mostly cellulose but also a smaller amount of a xylose-glucose copolymer. The CNF had a crystallinity index of 48% and showed typical peaks for the cellulose I allomorph.

Abstract [sv]

Algodling är en stor industri i Asien, men i stort sett outvecklad i Sverige. Algodling erbjuder många fördelar jämfört med odling av landbaserad biomassa. Algodlingar upptar inte värdefulla landområden och kräver ingen konstbevattning eller gödningsmedel vilket förebygger övergödning i kustnära miljöer. Alger är en potentiell råvara för framställning av biobränslen och biobaserade material. Syftet med detta avhandlingsarbete var att utveckla metoder för att extrahera och strukturbestämma polysackarider från makroalger som odlats på västkusten i Sverige. De extraherade polysackariderna användes sedan för att framställa några olika biobaserade material. I den första studien utvecklades en metod för att fraktionera proteiner och polysackarider från den röda makroalgen Porphyra. En proteinfraktion och tre polysackaridfraktioner erhölls vid fraktioneringen. I den andra studien utvecklades två olika protokoll för att extrahera polysackariden ulvan från två olika arter den gröna makroalgen Ulva. Extraktion med saltsyralösning gav ett högre utbyte av ulvan än extraktion med vatten. Sammansättningen av monosackarider hos det extraherade ulvanet varierade beroende på vilken extraktionsmetod som användes och även på vilken art av Ulva som användes. I den tredje studien tillverkades hydrogeler av ulvan som extraherats från Ulva. Ulvan oxiderades först till ulvan dialdehyd och blandades sedan med gelatin vilket ledde till bildningen av hydrogeler. Hydrogelerna visade en god svällningsförmåga i vatten och god förmåga att adsorbera färgämnet metylenblått. Hydrogelerna adsorberade också tungmetalljoner i viss utsträckning. I den fjärde studien extraherades cellulosa från Ulva och den extraherade cellulosan användes sedan vidare för att tillverka nanocellulosa (CNF) och regenererad cellulosa. Kemisk analys av nanocellulosan visade att den innehåller mest cellulosa, men även en mindre mängd av en xylos-glukossampolymer. Kristalliniteten uppmättes till 48% och det uppmätta XRD difraktogrammet indikerade förekomst av allomorfen cellulosa I.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2020. p. 100
Series
TRITA-CBH-FOU ; 2020:22
Keywords
biorefinery, seaweed, macroalgae, Ulva, Porphyra, ulvan, porphyran, cellulose, gelatin, hydrogel, heavy metal, methylene blue
National Category
Natural Sciences
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-272988 (URN)978-91-7873-493-1 (ISBN)
Public defence
2020-06-08, https://kth-se.zoom.us/webinar/register/WN_vojxcjeWSYuQqCNFZR_yiw, 144 28, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Foundation for Strategic Research , RBP14-0045
Note

QC 2020-05-07

Available from: 2020-05-07 Created: 2020-05-04 Last updated: 2020-05-15Bibliographically approved

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