Change search
ReferencesLink to record
Permanent link

Direct link
Excellent chemical and material cellulose from tunicates: diversity in cellulose production yield and chemical and morphological structures from different tunicate species
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
2014 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 21, no 5, 3427-3441 p.Article in journal (Refereed) Published
Abstract [en]

The high crystallinity and the high microfibrils aspect ratio of tunicate cellulose (TC) indicate TC's excellent chemical and material applications. However, its quantity and quality from different species have never been systematically reported and compared. In this study, the tunics of Ciona intestinalis (CI), Ascidia sp. (AS), Halocynthia roretzi (HR) and Styela plicata (SP) were processed to TC after an identical prehydrolysis-kraft cooking-bleaching sequence, while the tunicate fibrils were chemically and structurally characterized in situ and during the sequence. All tunics studied were composed of crystalline cellulose embedded with protein, lipids, sulfated glycans and mucopolysaccharides. The native composite structures are all very compact. However, the tunics from Phlebobranchia order (CI and AS) are soft, while those from Stolidobranchia, HR and SP, are hard. Fibrous cellulose could be prepared after removing the lipids, sulfated glycans and mucopolysaccharides through prehydrolysis, protein removal through kraft cooking and a final purification by bleaching. The final product is similar to 100 % pure cellulose which is in large molecular masses, composed of highly crystalline I-beta crystals, in elementary microfibrils form, with high specific surface area and thermal stability. There were lower TC yields from the soft tunics than from the hard ones. The cellulose fibrils had a section shape of lozenges with higher crystallinity. This study demonstrates that TC could be obtained in different yields and exhibited different chemical and morphological structures depending on the species. There is a great potential of tunicate resources for preparing excellent chemical and material cellulose.

Place, publisher, year, edition, pages
2014. Vol. 21, no 5, 3427-3441 p.
Keyword [en]
Tunicate cellulose, Ciona intestinalis, Ascidia sp., Halocynthia roretzi, Styela plicata, Chemical processing, Characterization
National Category
Polymer Technologies
URN: urn:nbn:se:kth:diva-153243DOI: 10.1007/s10570-014-0348-6ISI: 000341489300025OAI: diva2:756122

QC 20141016

Available from: 2014-10-16 Created: 2014-10-03 Last updated: 2015-06-15Bibliographically approved
In thesis
1. Towards Large-scale and Feasible Exploitation of Tunicate Cellulose and Cellulose Nanocrystals for Different Applications
Open this publication in new window or tab >>Towards Large-scale and Feasible Exploitation of Tunicate Cellulose and Cellulose Nanocrystals for Different Applications
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Tunicates are a group of filter-feeding animals that live in the ocean. They are widely distributed throughout the world and are a major contributor to the fouling problem in aquaculture. In addition to their natural abundance, large-scale farming will further render them readily available in high quantities, and they should instead be providing us food, energy, chemicals and materials. As tunicates are the sole known animal group synthesizing cellulose, the primary target for this bioresources exploitation should be cellulose preparation and application. Moreover, cellulose exploitation should be conducted in both a technically and economically feasible manner.

Among the tunicates, Ciona intestinalis (termed Ciona hereafter) is one of the most abundant species in Norwegian and Swedish coastal waters. Upon comprehensive quantification of the principal chemical compositions, cellulose has been confirmed to exist as cellulose-protein fibrils cemented by non-cellulose glycans and lipids and is almost exclusively present in the Ciona tunic fraction. Using the tunic as raw material, Ciona cellulose was prepared following a unique prehydrolysis-kraft cooking-bleaching sequence with a yield of 21.64% and by a modified Updegraff method with a yield of 23.65% on a dried ash-free mass basis. To improve the Ciona cellulose dispersibility and processability, Ciona cellulose nanocrystals (CNs) were prepared using different processes, namely acid hydrolysis, 2,2,6,6‑tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation and enzymatic hydrolysis as well as acid hydrolysis followed by TEMPO-mediated oxidation. The CN preparation yield was 30.0-73.4%, depending on the process applied.

By conducting comprehensive characterizations, it was found that the Ciona cellulose was nearly 100% pure, with a large weight average degree of polymerization (DPw=4200), a high surface area (133 m2/g), a large aspect ratio (length of several micrometres and diameter of ~16 nm), a high crystallinity (89%) in the form of nearly pure Iβ crystals, and a good thermal stability (onset degradation temperature of 226 ºC). When obtained in membrane form, the cellulose preserved the native interwoven microfibril network structure in the original tunic. It had a high ductility (tensile strain of 19.24%) in the wet state and good mechanical strength (tensile strength of 41.19 MPa and Young’s Modulus of 1.98 GPa) when dried. The CNs obtained were smaller in DPw, shorter in morphological size (length), similar or higher in crystallinity and more thermally stable than the starting cellulose to different extents and with different charged structures and charge contents dependent on the method/procedure used.

Several applications have been examined. First, the Ciona cellulose in pulp form was utilized in the fabrication of sponge cloth to replace cotton, and the product obtained was of similar quality to the commercial one made from cotton. Second, the Ciona cellulose in membrane form was tested in the cultivation of human umbilical vein endothelial cells and mouse NIH‑3T3 cells for evaluations of cell proliferation performance and medical application potential. The performance was very positive. Third, the Ciona cellulose membrane and two CNs were applied as the matrix for high-quality zinc-blende CdSe/CdS core/shell nanocrystal quantum dots (QDs) for the development of mechanically strong and high-performance fluorescent material. The QDs were firmly attached to the Ciona CNs with uniform monolayer distribution and a high packing density. The obtained composites preserved both the high-quality optical properties from the QDs and the matrix morphology and thus expectedly the excellent mechanical properties from the cellulose. Finally, the Ciona CNs were processed to composite films cemented by konjac glucomannan for material development. Newly introduced hydrogen bonds between these two compatible polysaccharides and thus strong cementing effects were observed. The composite films showed excellent mechanical properties in addition to improved transparency, thermal stability and hydrophobicity compared with the CN’s neat films.

Feasible tunicate cellulose exploitation demands the sound large-scale farming of Ciona for the highest possible cellulose content in the farmed animal, the exploitation of species other than Ciona, the complete utilization of fractions other than the tunic used and the value-added productions of other by-products. Composition quantification of the adult Ciona specimens collected from different farms showed that the carbohydrate content was linearly correlated with the body weight, which in turn was affected by the farm location, deployment time and sub-sea depth of the settling structures. Through analysing the Ciona intestinal content, it was found that both eukaryotes and prokaryotes contributed to the diet of the animal, and their quantities were positively correlated with the animal size (body weight). The tunics of three other tunicate species, Halocynthia roretzi, Styela plicata, and Ascidia sp., have been examined for tunicate cellulose preparation following the prehydrolysis-kraft cooking‑bleaching procedure. They were all found to be good sources for similar quality tunicate cellulose exploitation, thus verifying the universal applicability of the procedure. Based on more detailed chemical composition analyses, all the fractions other than the tunic, termed the inner body tissues fraction, from all four tunicate species were found to have excellent nutritional values: a high protein content with good quality amino acids and high contents of omega-3 (n-3) fatty acids and essential elements. Their toxic element contents were under the regulated limits for human food. They should therefore all be explored as human food sources. Furthermore, many different chemical structures, many of which were found for the first time, were present in the tunicate animals studied, ranging from collagens, glycosaminoglycans, and sterols to phospholipids. These structures should be explored as various bioactive by‑products during tunicate cellulose exploitation. For example, the prepared Ciona lipids had a high content of n-3 fatty acids, which presented mainly in the form of phospholipids. They should be an excellent alternative to markedly high value fish oils, but with a higher bioavailability.

The techniques and knowledge obtained by this study will provide a basis for the promising large-scale and feasible exploitation of tunicate cellulose and cellulose nanocrystals for different applications.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. 70 p.
TRITA-CHE-Report, ISSN 1654-1081 ; 2015:24
National Category
Polymer Chemistry
urn:nbn:se:kth:diva-169483 (URN)978-91-7595-576-6 (ISBN)
Public defence
2015-06-11, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)

QC 20150615

Available from: 2015-06-15 Created: 2015-06-15 Last updated: 2015-06-15Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Search in DiVA

By author/editor
Zhao, YadongLi, Jiebing
By organisation
Fibre and Polymer Technology
In the same journal
Cellulose (London)
Polymer Technologies

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 65 hits
ReferencesLink to record
Permanent link

Direct link