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Cyclic fractionation process for Saccharina latissima using aqueous chelator and ion exchange resin
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.ORCID iD: 0000-0003-3745-4092
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.ORCID iD: 0000-0002-1631-1781
2017 (English)In: Journal of Applied Phycology, ISSN 0921-8971, E-ISSN 1573-5176, Vol. 29, no 6, p. 3175-3189Article in journal (Refereed) Published
Abstract [en]

A new approach to process Saccharina latissima algal biomass was developed using sodium citrate and a polyvalent cation-specific resin to sequentially extract the alginate into several usable fractions. The fractionation was performed in a cyclic manner, utilizing a stepwise removal of the native polyvalent ions present in the algae to isolate fractions of alginate with different solubility in the presence of these ions. Sodium citrate was used in different concentrations in the extraction solution to remove polyvalent cations to adjust the alginate liberation while AMBERLITE IRC718 resin was added to further remove these ions and regenerate the extraction solution. Alginate was recovered by acid precipitation and analyzed for its uronic acid composition and molecular weight, and the carbohydrate compositions of the insoluble and soluble parts of the algal biomass residue were determined. Finally, the fractionation method was assessed with a life cycle analysis to determine the energy and water efficiency as well as the greenhouse gas emissions and the results were compared to conventional alkaline extraction. The results indicate that the energy and water use as well as the emissions are considerably lower for the cyclic extraction in comparison with the conventional methods.

Place, publisher, year, edition, pages
2017. Vol. 29, no 6, p. 3175-3189
Keywords [en]
Extraction, Fractionation, Alginate, Saccharina latissima, Phaeophyceae, Chelation, Ion exchange resin
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:kth:diva-220268DOI: 10.1007/s10811-017-1176-5ISI: 000416446400042Scopus ID: 2-s2.0-85020641776OAI: oai:DiVA.org:kth-220268DiVA, id: diva2:1173160
Note

QC 20180111

Available from: 2018-01-11 Created: 2018-01-11 Last updated: 2018-11-20Bibliographically approved
In thesis
1. POLYMER EXTRACTION AND UTILIZATION OF BROWN ALGAL BIOMASS
Open this publication in new window or tab >>POLYMER EXTRACTION AND UTILIZATION OF BROWN ALGAL BIOMASS
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Aquaculture is a field with a world changing potential. The areas at sea are enormous and aquatic cultivations impact both the environment and local ecology far less than land based cultivations. In the realm of algae, abundancies exists of nutrition, water and accessible sunlight, but there is constant shortage of places to dwell. In an algae farm, the algae are given free space to dwell on a seeding line, the growth is massive. In the Swedish research project Seafarm, which this work belongs to, a 4500 m long line gives 15 kg/m of Saccharina latissima brown algae in each harvest. This is a thesis on how to process the algal biomass and generate materials. The algal component alginate, which is a natural charged polymer, is the main thread along the entire thesis, both in the beginning, when focus lies on extraction and in the end when alginate materials are made.

In an algal extraction-study the impact of chelation-strength parameter was assessed. Salts with different ability to chelate ions were used in the extraction process, sodium citrate was found to be the most promising extraction salt to liberate alginate.

A cyclic process, in which a sodium citrate solution was regenerated and reused, was developed and assessed. An interesting effect of the new process was that it allowed for a fractionation of alginate into several qualities with different uronic acid composition (the two building blocks of alginate). This fractionation was scaled up to supply enough alginate to support a material study to evaluate the individual properties of the different fractions.

Alginate gel filaments were made by extruding alginate into calcium chloride solution, in which if forms gels. Certain gels were also exposed to aluminum chloride. The filaments were tested for their tensile properties. An interesting trend in the relation between gel strength and uronic acid composition also inspired a theoretical study to establish the mechanism behind the observed trends. Gel-filaments were drawn in solutions of different alginate interacting salts, then dried into thin filaments and subjected to tensile testing. The treatments increased the modulus of the filaments and also increased their stress-at-break. The tensile properties were comparable to that of other natural derived fibers such as hemp fiber or cotton cellulose.

Compatibilizers were developed to tune the surface energy of the filaments and approach that of polymers used in fiber reinforced composites. The compatibilizers were made of linseed oil that was grafted with maleic anhydride to attach charged groups. The graft modified oil was added to alginate filaments which were tensile-tested.

Abstract [sv]

Akvakultur har världsförändringspotential. Havets vidder är enorma och akvatiska odlingar påverkar miljön och den lokala ekologin långt mindre än jordbruket på land. I algernas domäner finns det rikligt med näring, vatten och tillgängligt solljus, men det är en konstant brist på fria ytor att växa på. När en algfarm förser algerna med utrymmet på ett helt rep och de får växa ostört, då växer det så det knakar. I det svenska forskningsprojektet Seafarm, som finansierat detta arbete, ger ett 4500 m långt rep 15 kg/m Saccharina latissima brunalger, vid varje skörd. Den här avhandlingen är en studie i algbiomassabearbetning och hur nya material av biomassan kan framställas. Alginat, som är en av algens beståndsdelar, och en naturlig laddad polymer, är den röda tråden genom hela avhandlingen, både i början, där fokus låg på extraktion och i slutet där olika alginatmaterial preparerades.

I en inledande studie undersöktes effekten av kelatering vid extraktionerna. Salter med olika jonkelateringsförmåga användes i extraktioner, och användningen av natriumcitrat visade sig vara mest fördelaktigt i extraktionslösningar för att utvinna alginat.

Med utgångspunkt i den inledande extraktionsprocessen utvecklades en ny cyklisk process då natriumcitratlösningen regenererades och återanvändes. Den nya processen utvärderades och en intressant effekt var att den möjliggjorde utvinning av alginat i flera olika fraktioner med olika uronsyrasammansättning (de två byggstenarna i alginat). Denna fraktionering skalades upp för att renframställa tillräckligt med alginat för att kunna testa fraktionerna in en materialstudie.

I materialstudien gjordes geltrådar genom att extrudera alginat ner i en kalciumkloridlösning, där de gelade. Några geler exponerades också för aluminiumklorid. Trådarna dragprovades och resultaten visade ett intressant samband mellan gelstyrka och uronsyrasammansättning vilket inspirerade oss till att göra en teoretisk studie för att klarlägga ursprunget till trenden.

Geltrådar gjordes också till tunna fibrer i en process där de först extruderades, sedan drogs ut i olika saltlösningar och slutligen torkades. När fibrerna dragprovades visade det sig att de hade hög elasticitetsmodul och hög dragstyrka. Dragstyrkan var i samma storleksordning som t.ex. hampafiber eller bomullsfiber.

En kompatibilisator utvecklades för att anpassa ytenergin hos alginatfibrerna och i en riktning att för att likna plaster som brukar fiberförstärkas. Kompatibilisatorn framställdes av linolja som ympades med maleinsyraanhydrid för att fästa laddade grupper på den. Denna nya komponent inkorporerades i fibrer tillsammans med alginat och fibrerna dragprovades.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2018. p. 88
Series
TRITA-CBH-FOU ; 2018:58
Keywords
Algae, Saccharina latissima, alginate, brown seaweed, extraction, filament, chelation, gel
National Category
Polymer Chemistry
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-239160 (URN)978-91-7873-025-4 (ISBN)
Public defence
2018-12-07, F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Research Council Formas, 2013-92
Note

QC 20181119

Available from: 2018-11-19 Created: 2018-11-16 Last updated: 2018-11-19Bibliographically approved

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