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Polysaccharides from red and green seaweed: Extraction, characterisation and applications
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymer Technology.
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 [en]
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: urn:nbn:se:kth:diva-272988ISBN: 978-91-7873-493-1 (print)OAI: oai:DiVA.org:kth-272988DiVA, id: diva2:1428151
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
List of papers
1. A Strategy for the Sequential Recovery of Biomacromolecules from Red Macroalgae Porphyra umbilicalis Kützing
Open this publication in new window or tab >>A Strategy for the Sequential Recovery of Biomacromolecules from Red Macroalgae Porphyra umbilicalis Kützing
2018 (English)In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 57, no 1, p. 42-53Article in journal (Refereed) Published
Abstract [en]

A nondestructive, multicomponent fractionation strategy has been developed to extract proteins and polysaccharides from the red macroalgae Porphyra umbilicalis collected along the west coast of Sweden and cultivated indoors under controlled conditions. First, a protein-rich fraction was extracted in an ice-cold alkaline solution. The overall protein content in Porphyra umbilicalis was estimated to be 30.6% of the dry weight, and out of that, 15.0% could be recovered. Water-soluble polysaccharides were then extracted from the insoluble residual fraction using sequential alkaline and acidic treatments at 90 °C for 4 h. Spectroscopic and chromatographic analyses of the polysaccharide fractions show that high-molecular-weight carrageenans were obtained from the alkaline extraction and a galactose-rich pectin substance was obtained from the acidic extraction. The insoluble fraction remaining after all extraction steps was rich in cellulose. An elemental analysis of Porphyra umbilicalis via scanning electron microscopy with energy-dispersive X-ray spectrometry (SEM-EDS) showed the presence of C, O, Na, Ca, Mg, Al, Cl, and S. However, no heavy metals or other toxic elements, such as Pb, Hg, and As, were found.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2018
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-221687 (URN)10.1021/acs.iecr.7b03768 (DOI)000419999800003 ()2-s2.0-85040457542 (Scopus ID)
Note

QC 20180122

Available from: 2018-01-22 Created: 2018-01-22 Last updated: 2020-05-04Bibliographically approved
2. Composition and structure of cell wall ulvans recovered from Ulva spp. along the Swedish west coast
Open this publication in new window or tab >>Composition and structure of cell wall ulvans recovered from Ulva spp. along the Swedish west coast
Show others...
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
Keywords
Ulva spp., Ulvan, Extraction, Composition, Sulfation, Structure
National Category
Basic Medicine
Identifiers
urn:nbn:se:kth:diva-269441 (URN)10.1016/j.carbpol.2020.115852 (DOI)000513914400029 ()32059903 (PubMedID)2-s2.0-85077645228 (Scopus ID)
Note

QC 20200316

Available from: 2020-03-16 Created: 2020-03-16 Last updated: 2020-05-04Bibliographically approved
3. Ulvan dialdehyde-gelatin hydrogels for removal of heavy metals and methylene blue from aqueous solution
Open this publication in new window or tab >>Ulvan dialdehyde-gelatin hydrogels for removal of heavy metals and methylene blue from aqueous solution
Show others...
(English)Manuscript (preprint) (Other academic)
Keywords
Ulva fenestrata, Ulva lactuca, gelatin, hydrogel, heavy metal, methylene blue, adsorption
National Category
Natural Sciences
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-272987 (URN)
Funder
Swedish Foundation for Strategic Research , RBP14-0045
Note

QC 20200506

Available from: 2020-05-04 Created: 2020-05-04 Last updated: 2020-05-06Bibliographically approved
4. Cellulose from the green macroalgae ulva lactuca: isolation, characterization, optotracing, and production of cellulose nanofibrils
Open this publication in new window or tab >>Cellulose from the green macroalgae ulva lactuca: isolation, characterization, optotracing, and production of cellulose nanofibrils
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2020 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882XArticle in journal (Refereed) Published
Abstract [en]

We report (1) successful extraction and characterization of cellulose from northern hemisphere green macroalgae Ulva lactuca (Ulva fenestrata) collected along the Swedish west coast and cultivated indoors under controlled conditions, followed by (2) its utilization in the production of lignin-free cellulose nanofibrils (CNF). Cellulose was extracted by sequential treatment with ethanol, hydrogen peroxide, sodium hydroxide, and hydrochloric acid, yielding a cellulose-rich insoluble fraction. The extracted cellulose was disintegrated into CNF using a mechanical homogenization process without any further enzymatic pre-treatments. In addition, regenerated cellulose was prepared. XRD characterization of the CNF showed characteristic peaks for the cellulose I allomorph and confirmed that the nanofibrils were semicrystalline with a crystallinity index of 48%. Regenerated cellulose was mostly amorphous with an XRD pattern indicating the presence of the cellulose II allomorph. The cellulose fractions were essentially free from inorganic substances and thermally stable up to around 260 degrees C. Structural mapping with CP-MAS C-13-NMR sustains the cellulose content of CNF and regenerated cellulose, respectively, yet ion chromatography identified the presence of 10-15% xylose in the fractions. Optotracing was used as a novel and non-disruptive tool to selectively assess the polysaccharide composition of the cellulose fractions and produced CNF aiming to shed light on this hitherto non-resolved origin of xylose in Ulva cell wall matter. Fluorescence excitation and emission spectra of a panel of 4 oligothiophenes identified and verified the presence of cellulose and sustain the conclusion that the isolated fractions consist of cellulose intertwined with a small amount of a xylose-containing glucan copolymer.

Keywords
Nanocellulose, CNF, Extraction, Macroalgae, Ulva lactuca, Ulva fenestrata, Optotracing
National Category
Natural Sciences
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-272986 (URN)10.1007/s10570-020-03029-5 (DOI)000515972600002 ()2-s2.0-85079113064 (Scopus ID)
Funder
Swedish Foundation for Strategic Research , RBP14-0045
Note

QC 20200505

Available from: 2020-05-04 Created: 2020-05-04 Last updated: 2020-05-11Bibliographically approved

Open Access in DiVA

The full text will be freely available from 2020-12-31 10:00
Available from 2020-12-31 10:00

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Wahlström, Niklas

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