Aaltodoc Repository :: Browsing by Author "Arola, Suvi"

Browsing by Author "Arola, Suvi"

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Binding of cellulose binding modules reveal differences between cellulose substrates
(2016-10-17) Arola, Suvi; Linder, Markus B.; Department of Biotechnology and Chemical Technology; Department of Bioproducts and Biosystems; Biomolecular Materials
The interaction between cellulase enzymes and their substrates is of central importance to several technological and scientific challenges. Here we report that the binding of cellulose binding modules (CBM) from Trichoderma reesei cellulases Cel6A and Cel7A show a major difference in how they interact with substrates originating from wood compared to bacterial cellulose. We found that the CBM from TrCel7A recognizes the two substrates differently and as a consequence shows an unexpected way of binding. We show that the substrate has a large impact on the exchange rate of the studied CBM, and moreover, CBM-TrCel7A seems to have an additional mode of binding on wood derived cellulose but not on cellulose originating from bacterial source. This mode is not seen in double CBM (DCBM) constructs comprising both CBM-TrCel7A and CBM-TrCel6A. The linker length of DCBMs affects the binding properties, and slows down the exchange rates of the proteins and thus, can be used to analyze the differences between the single CBM. These results have impact on the cellulase research and offer new understanding on how these industrially relevant enzymes act.
Bioactive Fiber Foam Films from Cellulose and Willow Bark Extract with Improved Water Tolerance
(American Chemical Society, 2024-02-20) Lohtander, Tia; Koso, Tetyana; Huynh, Ngoc; Hjelt, Tuomo; Gestranius, Marie; King, Alistair W.T.; Österberg, Monika; Arola, Suvi; Department of Bioproducts and Biosystems; Bioproduct Chemistry; VTT Technical Research Centre of Finland
Cellulose-based materials are gaining increasing attention in the packaging industry as sustainable packaging material alternatives. Lignocellulosic polymers with high quantities of surface hydroxyls are inherently hydrophilic and hygroscopic, making them moisture-sensitive, which has been retarding the utilization of cellulosic materials in applications requiring high moisture resistance. Herein, we produced lightweight all-cellulose fiber foam films with improved water tolerance. The fiber foams were modified with willow bark extract (WBE) and alkyl ketene dimer (AKD). AKD improved the water stability, while the addition of WBE was found to improve the dry strength of the fiber foam films and bring additional functionalities, that is, antioxidant and ultraviolet protection properties, to the material. Additionally, WBE and AKD showed a synergistic effect in improving the hydrophobicity and water tolerance of the fiber foam films. Nuclear magnetic resonance (NMR) spectroscopy indicated that the interactions among WBE, cellulose, and AKD were physical, with no formation of covalent bonds. The findings of this study broaden the possibilities to utilize cellulose-based materials in high-value active packaging applications, for instance, for pharmaceutical and healthcare products or as water-resistant coatings for textiles, besides bulk packaging materials.
Bioactive Films from Willow Bark Extract and Nanocellulose Double Network Hydrogels
(FRONTIERS MEDIA SA, 2021-08-12) Lohtander, Tia; Grande, Rafael; Österberg, Monika; Laaksonen, Päivi; Arola, Suvi; Department of Bioproducts and Biosystems; Bioproduct Chemistry; Häme University of Applied Sciences; VTT Technical Research Centre of Finland
In nature, the protection of sensitive components from external threats relies on the combination of physical barriers and bioactive secondary metabolites. Polyphenols and phenols are active molecules that protect organisms from physical and chemical threats such as UV irradiation and oxidative stress. The utilization of biopolymers and natural bioactive phenolic components as protective coating layers in packaging solutions would enable easier recyclability of materials and greener production process compared with the current plastic-based products. Herein, we produce a fully wood-based double network material with tunable bioactive and optical properties consisting of nanocellulose and willow bark extract. Willow bark extract, embedded in nanocellulose, was cross-linked into a polymeric nanoparticle network using either UV irradiation or enzymatic means. Based on rheological analysis, atomic force microscopy, antioxidant activity, and transmittance measurements, the cross-linking resulted in a double network gel with enhanced rheological properties that could be casted into optically active films with good antioxidant properties and tunable oxygen barrier properties. The purely biobased, sustainably produced, bioactive material described here broadens the utilization perspectives for wood-based biomass, especially wood-bark extractives. This material has potential in applications where biodegradability, UV shielding, and antioxidant properties of hydrogels or thin films are needed, for example in medical, pharmaceutical, food, and feed applications, but also as a functional barrier coating in packaging materials as the hydrogel properties are transferred to the casted and dried films.
Biochemical modification and functionalization of nanocellulose surface
(VTT Technical Research Centre of Finland, 2015) Arola, Suvi; Biotekniikan ja kemian tekniikan laitos; Department of Biotechnology and Chemical Technology; Kemian tekniikan korkeakoulu; School of Chemical Technology; Linder, Markus, Prof., Aalto University, Department of Biotechnology and Chemical Technology, Finland
Cellulose is an abundant biopolymer found in many different organisms ranging from microbes to plants and animals. The homopolymer, composed of repeating glucose units, forms mechanically strong nanosized fibrils and rods. In plants cellulose forms macroscopic fibers, which are incorporated in the cell walls. Recently, it has been shown that cellulose fibers can be disintegrated into the fibrils and rods by different chemical treatments. These materials are called nanocellulose. Nanocellulose is a promising material to replace fossil based materials because it is renewable, biodegradable and abundant. It holds great potential in many applications due to its superior mechanical properties and large surface area. For most applications modification of nanocellulose surface is needed due to its tendency to aggregate by hydrogen bonding to adjacent cellulose surfaces. In this thesis we took a biochemical approach on nanocellulose surface modification to achieve modified and functional materials. The advantages of this approach are that the reactions are done in mild aqueous ambient conditions and the amount of functionalities of biomolecules is broad. Four different approaches were chosen. First, genetically engineered cellulose binding proteins, were used to introduce amphiphilic nature to nanocellulose in order to create surface self-assembled nanocellulose films and to stabilize emulsions. This method was shown to be a good method for bringing new function to nanocellulose. (Publication I) Second, covalent coupling of enzymes directly onto modified nanocellulose surfaces provided a route for protein immobilization in bulk. Nanocellulose derivatives were shown to be well suited platforms for easy preparation of bioactive films. More over the film properties could be tuned depending on the properties of the derivative. (Publication II) Third, by modifying the nanocellulose surface with specific enzymes we could study the role of hemicellulose in nanocellulose fibril surface interactions. We showed that hemicellulose has an important role in nanofibrillated cellulose networks, yet its effects were different in aqueous and dry matrixes. (Publication III) Fourth, by modifying the specific function of cellulose binding protein via genetic engineering we showed how the binding properties can be altered and thus the functionalization properties can be tuned, and that the cellulose binding protein properties are substrate dependent. We also showed that nanocellulose as a model substrate in binding studies is a valuable tool for gaining new insight in protein binding behavior. (Publication IV) In conclusion, we showed that biochemical methods are feasible in nanocellulose modification and functionalization to study intrinsic properties of nanocellulose and cellulose binding proteins but also for creating new functional materials.
Biomordanting willow bark dye on cellulosic materials
(WILEY-BLACKWELL, 2020-02-01) Lohtander, Tia; Arola, Suvi; Laaksonen, Päivi; Department of Bioproducts and Biosystems; Nanostructures and Materials; Bioproduct Chemistry
A semi-quantitative study of willow bark dye adsorption on two different cellulose materials using biomordants was carried out. The studied celluloses were microcrystalline cellulose (MCC) AaltoCell and regenerated Ioncell-F (IC) fibres. The dye was a hot water extract of willow bark and the adsorption to cellulose was carried out using carboxylic acid-containing biomordants, namely, oxalic acid, citric acid and tannic acid. Alum was employed as the reference mordant. A semi-quantitative estimation of the dye uptake was conducted using high-performance liquid chromatography equipped with a diode array detector and also by visual inspection, as well as an evaluation of the coloration using CIELab parameters. The mechanism of the dye adsorption on the cellulose surfaces was studied via Fourier Transform–infrared spectroscopy. According to the results, MCC had a higher affinity for polyphenolic dye than the regenerated cellulose fibres. Dye uptake on MCC was 50%-80% and 44%-57% on IC. For MCC, the biomordants improved the dye uptake more effectively than the control mordant, alum, whereas for IC the biomordants were less effective than alum.
Capturing colloidal nano- and microplastics with plant-based nanocellulose networks
(Nature Publishing Group, 2022-04-05) Leppänen, Ilona; Lappalainen, Timo; Lohtander, Tia; Jonkergouw, Christopher; Arola, Suvi; Tammelin, Tekla; Department of Bioproducts and Biosystems; Biomolecular Materials; VTT Technical Research Centre of Finland
Microplastics accumulate in various aquatic organisms causing serious health issues, and have raised concerns about human health by entering our food chain. The recovery techniques for the most challenging colloidal fraction are limited, even for analytical purposes. Here we show how a hygroscopic nanocellulose network acts as an ideal capturing material even for the tiniest nanoplastic particles. We reveal that the entrapment of particles from aqueous environment is primarily a result of the network’s hygroscopic nature - a feature which is further intensified with the high surface area of nanocellulose. We broaden the understanding of the mechanism for particle capture by investigating the influence of pH and ionic strength on the adsorption behaviour. We determine the nanoplastic binding mechanisms using surface sensitive methods, and interpret the results with the random sequential adsorption (RSA) model. These findings hold potential for the explicit quantification of the colloidal nano- and microplastics from different aqueous environments, and eventually, provide solutions to collect them directly on-site where they are produced.
Combining Rigid Cellulose Nanocrystals and Soft Silk Proteins: Revealing Interactions and Alignment in Shear
(Wiley-Blackwell, 2023-07-17) Leppänen, Ilona; Arola, Suvi; King, Alistair W.T.; Unger, Miriam; Stadler, Hartmut; Nissen, Gry Sofie; Zborowski, Charlotte; Virtanen, Tommi; Salmela, Juha; Setälä, Harri; Lésage, Stephanie; Österberg, Monika; Tammelin, Tekla; Department of Bioproducts and Biosystems; Bioproduct Chemistry; VTT Technical Research Centre of Finland; Bruker Nano Surfaces Division Germany; Oxford Biomaterials Ltd.; Spinnova Oy
Natural materials, such as silk and cellulose, have an inspiring set of properties, which have evolved over hundreds of millions of years. In this study, cellulose nanocrystals (CNCs) and regenerated silk fibroin (RSF) are combined to evaluate their suitability for filament formation. This is assessed by tuning and characterizing the interactions between these two materials and finally by studying the alignment of the mixtures under shear. To modify the interactions between CNCs and silk, CNCs with varying surface functionalities (sulfate and/or aminosilane groups) are used. The interactions and compatibility of the two components are investigated using quartz crystal microbalance with dissipation monitoring (QCM-D) and photothermal atomic force microscopy (AFM-IR), which show that ionic interactions induce sufficient binding between the two components. Then, the alignment of the CNC and silk mixtures is evaluated by shear-induced polarized light imaging, which indicates that silk can orientate with the CNCs when not covalently bound. Finally, the potential of the materials for filament formation is tentatively demonstrated using an industrial dry-spinning environment, where CNCs are expected to bring order and alignment, whereas RSF provides soft and more mobile regions to further facilitate the alignment of the final filament structure.
Different effects of carbohydrate binding modules on the viscoelasticity of nanocellulose gels
(2020-07) Rooijakkers, Bart J.M.; Arola, Suvi; Velagapudi, Rama; Linder, Markus B.; Department of Bioproducts and Biosystems; Biohybrid Materials; Biomolecular Materials
Many cellulose degrading and modifying enzymes have distinct parts called carbohydrate binding modules (CBMs). The CBMs have been shown to increase the concentration of enzymes on the insoluble substrate and thereby enhance catalytic activity. It has been suggested that CBMs also have a role in disrupting or dispersing the insoluble cellulose substrate, but dispute remains and explicit evidence of such a mechanism is lacking. We produced the isolated CBMs from two major cellulases (Cel6A and Cel7A) from Trichoderma reesei as recombinant proteins in Escherichia coli. We then studied the viscoelastic properties of native unmodified cellulose nanofibrils (CNF) in combination with the highly purified CBMs to detect possible functional effects of the CBMs on the CNF. The two CBMs showed clearly different effects on the viscoelastic properties of CNF. The difference in effects is noteworthy, yet it was not possible to conclude for example disruptive effects. We discuss here the alternative explanations for viscoelastic effects on CNF caused by CBMs, including the effect of ionic cosolutes.
Effect of oxidation on cellulose and water structure : a molecular dynamics simulation study
(SPRINGER, 2021-05) Mudedla, Sathish Kumar; Vuorte, Maisa; Veijola, Elias; Marjamaa, Kaisa; Koivula, Anu; Linder, Markus B.; Arola, Suvi; Sammalkorpi, Maria; Department of Chemistry and Materials Science; Department of Bioproducts and Biosystems; Soft Materials Modelling; Clean Technologies; Biomolecular Materials; Department of Bioproducts and Biosystems; VTT Technical Research Centre of Finland
Enzymatic cleavage of glycocidic bonds is an important, green and biocompatible means to refine lignocellulosic biomass. Here, the effect of the resulting oxidation point defects on the structural and water interactions of crystalline cellulose {100} surface are explored using classical molecular dynamics simulations. We show that even single oxidations reduce the connections within cellulose crystal significantly, mostly via local interactions between the chains along the surface plane but also via the oxidation defects changing the structure of the crystal in direction perpendicular to the surface. Hydrogen bonding on the surface plane of cellulose is analyzed to identify onset of desorption of glucose chains, and the desorption probed. To assess the actual soluble product profile and their fractions resulting from lytic polysaccharide monooxygenase (LPMO) enzyme oxidation on real cellulose crystal samples, we employ High-Performance Anion-Exchange Chromatography with Pulsed Amperometric-Detection (HPAEC-PAD) technique. The findings demonstrate the LPMO oxidation results in soluble glucose fragments ranging from 2 to 8 glucose units in length. Additionally, significantly more oxidized oligosaccharides were released in LPMO treatment of AaltoCell than Avicel, the two studied microcrystalline cellulose species. This is likely to result from the large reactive surface area preserved in AaltoCell due to manufacturing process. Furthermore, as can be expected, the oxidation defects at the surfaces lead to the surfaces binding a larger amount of water both via direct influence by the defect but also the defect induced protrusions and fluctuations of the glucose chain. We quantify the enhancement of water interactions of cellulose crystals due to the oxidation defects, even when no desorption takes place. The molecular simulations indicate that the effect is most pronounced for the C1-acid oxidation (carboxylic acid formation) but present also for the other defects resulting from oxidation. The findings bear significance in understanding the effects of enzymatic oxidation on cellulose nanocrystals, the difference between cellulose species, and cleavage of soluble products from the cellulosic material.
Hemicellulose cross-linked nanocellulose as immobilization matrix for photosynthetic solid-state cell factories
(2021-08-24) Virkkala, Tuuli; Tammelin, Tekla; Arola, Suvi; Kemian tekniikan korkeakoulu; Bankar, Sandip
Photosynthetic microorganisms can be utilized to produce sustainable fuels and chemicals. These photosynthetic cell factories constitute a promising alternative to non-renewable fossil resources. However, technical challenges associated with suspension cultures, most prominently the light-to-product ratio coupled with high water and energy consumption, limits the realization of their theoretical potential. Immobilization i.e. binding the cells within a gel-like matrix is an interesting new technique that could be used to overcome these difficulties. It is vital that the matrix material used to immobilize the photosynthetic cells has sufficient wet mechanical properties to endure the submerged production conditions in addition to expressing biological compatibility with the cells. Recently, TEMPO-oxidized cellulose nanofibers (TCNFs) cross-linked with polyvinyl alcohol (PVA) has been reported as a superior alternative matrix material to the traditional alginate-based solutions. The purpose of this Master’s thesis was to investigate mixed-linkage glucan (MLG) as a natural polysaccharide-based alternative to the synthetic PVA with limited biodegradability. MLGs are hemicelluloses found as structural cross-linkers in the cell walls of grassy plants and they have been previously shown to create strong hydrogels with TCNF even with small concentrations. Rheological measurements and photosynthetic activity monitoring were used to study the mechanical properties and biocompatibility of MLG cross-linked TCNF (TCNF-MLGs). Three MLGs with different molecular weights were used in the experiments. All MLGs were shown to cross-link TCNF, and mechanical performance similar to PVA was obtained especially with the low molecular size MLG. TCNF-MLG expressed less variation in the matrix performance with and without the entrapped cyanobacterial cells than TCNF-PVA. The TCNF-MLG matrices were additionally shown to retain cell viability for up to 47 days. Overall, the results demonstrate that all-polysaccharidic matrices are feasible for microalgae immobilization in novel photosynthetic cell factories.
Interfacial Behavior of Recombinant Spider Silk Protein Parts Reveals Cues on the Silk Assembly Mechanism
(2018-09-05) Nilebäck, Linnea; Arola, Suvi; Kvick, Mathias; Paananen, Arja; Linder, Markus B.; Hedhammar, My; KTH Royal Institute of Technology; Department of Bioproducts and Biosystems; VTT Technical Research Centre of Finland
The mechanism of silk assembly, and thus the cues for the extraordinary properties of silk, can be explored by studying the simplest protein parts needed for the formation of silk-like materials. The recombinant spider silk protein 4RepCT, consisting of four repeats of polyalanine and glycine-rich segments (4Rep) and a globular C-terminal domain (CT), has previously been shown to assemble into silk-like fibers at the liquid-air interface. Herein, we study the interfacial behavior of the two parts of 4RepCT, revealing new details on how each protein part is crucial for the silk assembly. Interfacial rheology and quartz crystal microbalance with dissipation show that 4Rep interacts readily at the interfaces. However, organized nanofibrillar structures are formed only when 4Rep is fused to CT. A strong interplay between the parts to direct the assembly is demonstrated. The presence of either a liquid-air or a liquid-solid interface had a surprisingly similar influence on the assembly.
Modular Architecture of Protein Binding Units for Designing Properties of Cellulose Nanomaterials
(2015-10-05) Malho, J.-M.; Arola, Suvi; Laaksonen, Päivi; Szilvay, G.R.; Ikkala, Olli; Linder, Markus; VTT Technical Research Centre of Finland; Department of Biotechnology and Chemical Technology; Department of Materials Science and Engineering; Department of Applied Physics; Department of Bioproducts and Biosystems
Nanocellulose-based mechanically stable immobilization matrix for enhanced ethylene production
(ROYAL SOC CHEMISTRY, 2021-05-21) Rissanen, V.; Vajravel, S.; Kosourov, S.; Arola, Suvi; Kontturi, E.; Allahverdiyeva, Y.; Tammelin, T.; VTT Technical Research Centre of Finland; University of Turku; Materials Chemistry of Cellulose; Department of Bioproducts and Biosystems
Cell immobilization is a promising approach to create efficient photosynthetic cell factories for sustainable chemical production. Here, we demonstrate a novel photosynthetic solid-state cell factory design for sustainable biocatalytic ethylene production. We entrapped cyanobacteria within never-dried hydrogel films of TEMPO-oxidized cellulose nanofibers (TCNF) cross-linked with polyvinyl alcohol (PVA) to create a self-standing matrix architecture. The matrix is operational in the challenging submerged conditions and outperforms existing alginate-based solutions in terms of wet strength, long-term cell fitness, and stability. Based on rheological investigations, the critical strength of wet TCNF matrices is three times higher than in the existing immobilization matrices of alginate cross-linked with Ca2+. This is due to the rigid nature of the colloidal nanofiber network and the strong cross-linking with PVA, as opposed to polymeric alginate with reversible ionic Ca2+ bonds. The porous and hygroscopic nanofiber network also shields the cyanobacterial cells from environmental stress, maintaining photosynthetic activity during partial drying of films, and when submerged in the nutrient medium for long-term cultivation. Finally, TCNF matrices allow the ethylene-producing Synechocystis sp. PCC 6803 cells to operate in submerged conditions under high inorganic carbon loads (200 mM NaHCO3), where Ca2+-alginate matrices fail. The latter show severe cell leakage due to matrix disintegration already within 20 min of NaHCO3 supplementation. In contrast, TCNF-based matrices prevent cell leakage to the medium and restrict culture growth, leading to improved ethylene production yields. Furthermore, the operational capacity of the self-standing TNCF cell factory can be maintained long-term by periodically refreshing the nutrient medium. All in all, the results showcase the versatility and potential of cell immobilization with the never-dried colloidal TCNF matrix, paving the way towards novel biotechnological pathways using solid-state cell factories designed for efficient and sustainable production of e.g., monomers and fuels.
New insights on LPMO activities through AaltoCell and cellulose nanofibrils
(2019-12-17) Veijola, Elias; Arola, Suvi; Koivula, Anu; Kemian tekniikan korkeakoulu; Dahl, Olli
On the mechanism for the highly sensitive response of cellulose nanofiber hydrogels to the presence of ionic solutes
(SPRINGER, 2022-07) Arola, Suvi; Kou, Zhennan; Rooijakkers, Bart J.M.; Velagapudi, Rama; Sammalkorpi, Maria; Linder, Markus B.; Department of Chemistry and Materials Science; School common, CHEM; Department of Bioproducts and Biosystems; Soft Materials Modelling; Center of Excellence in Life-Inspired Hybrid Materials, LIBER; Biomolecular Materials
Hydrogels formed by cellulose nanofibers (CNFs) find use in a variety of applications. CNF hydrogels generally stiffen and ultimately flocculate with increasing salt concentrations. While charge repulsion explains the behavior of nanocellulose variants that have been stabilized by charged groups, it has been a puzzle why ions have such a pronounced effect also on CNFs with unmodified surfaces. We studied the effect of ionic solutes on native CNF hydrogels, and found that already at very low concentrations of around 1 mM, ions cause crowding of the hydrogels. The ionic solutes used were NaCl, Na2SO4, NaI, NaSCN, and sodium acetate. For the hydrogels, we used low densities of CNFs which lead to relatively weak gels that were highly sensitive to salts. Screening of the electrical double layer could not explain the results at such low ion concentrations. To understand cellulose-ion interactions, we used computational molecular dynamics simulations. The results provide an explanation by the effect of ions on the structure of the hydration layers of the cellulose. Understanding how and why ions affect the properties of native CNF hydrogels can help in for example manufacture of CNFs and when using CNFs as material components, substrates for enzymes, or as rheology modifiers. Ion-effects on the hydration layer of cellulose may also be important for more fundamental understanding of interfacial interactions of cellulose with water under different conditions. Graphical abstract: [Figure not available: see fulltext.].
Self-assembly of mixed-linkage glucan hydrogels formed following EG16 digestion
(Elsevier Science Ltd., 2025-01-01) McGregor, Nicholas G.S.; Penttilä, Paavo; Pitkänen, Leena; Mohammadi, Pezhman; Vuorte, Maisa; Igarashi, Kiyohiko; Arola, Suvi; Department of Bioproducts and Biosystems; Department of Chemistry and Materials Science; Wood Material Science; Biopolymer Chemistry and Engineering; Soft Materials Modelling; Center of Excellence in Life-Inspired Hybrid Materials, LIBER; Independent Researcher and Consultant, United Kingdom; University of Tokyo; VTT Technical Research Centre of Finland
Mixed-linkage glucans are major components of grassy cell-walls and cereal endosperm. Recently identified plant endo-β-glucanase from the EG16 family cleaves MLGs with strong specificity towards regions with at least four sequential β(1,4)-linked glucose residues. This activity yields a low molecular-weight MLG with a repeating structure of β(1,3)-linked cellotriose that gels rapidly at concentrations as low as 1.0 % w/v. To understand the gelation mechanism, we investigated the structure and behavior using rheology, microscopy, X-ray scattering, and molecular dynamics simulations. Upon digestion, the material's rheological behavior changes from typical polymeric material to a fibrillar network behavior seen for e.g. cellulose nanofibrils. Scanning electron microscopy and confocal microscopy verifies these changes in micro- and nanostructure. Small-angle X-ray scattering shows in-solution self-assembly of MLG through ~10 nm elemental structures. Wide-angle X-ray scattering data indicate that the polymer association is similar to cellulose II, with dominant scattering at d-spacing of 0.43 nm. Simulations of two interacting glucan chains show that β(1,3)-linkages prevent the formation of tight helices that form between β(1,4)-linked D-glucan chains, leading to weaker interactions and less ordered inter-chain assembly. Overall, these data indicate that digestion drives gelation not by enhancement of interactions driving self-assembly, but by elimination of unproductive interactions hindering self-assembly.
Stabilization of natural and synthetic indigo on nanocellulose network - Towards bioactive materials and facile dyeing processes
(ELSEVIER SCI LTD, 2021-12-15) Lohtander, Tia; Durandin, Nikita; Laaksonen, Timo; Arola, Suvi; Laaksonen, Päivi; Department of Bioproducts and Biosystems; Bioproduct Chemistry; Tampere University; Häme University of Applied Sciences; VTT Technical Research Centre of Finland
Synthetic dyes are vastly used for colouring numerous materials, although the adverse effects on environment are well recognized. In addition to developing the existing dyeing technologies more efficient and cleaner, the valorisation of natural dyes can enhance the sustainable development of dyeing industry. Natural indigo, derived from Isatis tinctoria, is a bio-based alternative for indigo produced via chemical synthesis routes. Owing to the insoluble character of indigo pigment, the dye requires conversion into soluble leucoindigo form prior to dyeing, which is often accomplished by using harsh sodium dithionite vat technique. During the processing from plant to dye attached on a fabric, indigo is transferred from the soluble leucoindigo form to the oxidized insoluble indigo and once more back to leucoindigo. Additionally, the oxidation is difficult to control and with traditional vat technique maintaining the leucoindigo through the dyeing often requires adding more reducing agent chemicals. Maintaining the soluble form throughout the process would enable lower number of processing steps and reduce the use of harmful chemical agents. In the present study, the stabilization of leucoindigo on nanocellulose matrix carrier was investigated with spectroscopic and photophysical methods. According to the results, leucoindigo was successfully stabilized on nanocellulose suspension, most likely due to the limited rate of oxygen diffusion into the viscous medium. Visual observations revealed that the leuco-form was retained even longer with natural indigo than synthetic indigo. This enhanced stability was attributed to the presence of radical scavenging species in natural indigo since the synthetic indigo did not show notable antioxidant properties. Given the promising results the paste formulation was demonstrated to be applicable for creating patterns on cotton using a screen-printing technique. Since the leucoindigo was stabilized on nanocellulose carrier, the need for re-reduction prior to dyeing was avoided and the amount of harmful reducing chemicals was reduced. These findings also show that the characteristics of natural dyes that are often considered disadvantageous compared to synthetic dyestuff, i.e. presence of co-products in the mixture, can however, create more value to the dyed material through new functionalities.
Sustainable dyeing of cellulosic materials with willow bark extract
(2018-04-03) Lohtander, Tia; Arola, Suvi; Kemian tekniikan korkeakoulu; Laaksonen, Päivi
The usage of natural dyes has been gradually vanishing since synthetic dyes were discovered and nowadays the annual share of natural dyes is approximately 1 %. However, the increasing awareness of environmental issues has raised demand for more sustainable and eco-friendly dyes, which are not dependent on petrochemical source. The natural dyes can be extracted from various sources and nature offers a wide range of different colored compounds, which can be used to all materials ranging from protein-based fiber, to cellulose fibers and to synthetic fibers. Natural dyes are secondary metabolites, i.e. they provide protection for the plant against external stress, and thus natural dyes have potential to bring new functionalities to dyed materials. However, natural dyes have generally weaker light and wash fastness properties than synthetic dyes. The main objective of this work was to study dyeing of four different cellulose-based materials with natural dye extracted from willow bark. The used cellulose materials were microcrystalline cellulose (MCC), Ioncell (IC), TEMPO oxidized cellulose nanofibrils (TEMPO-CNF) and pure cellulose paper. The influence of concentrations, pretreatments and dyeing conditions to final obtained color were analyzed by UV-Vis spectroscopy. According to UV-Vis spectroscopy and visual observations, the highest mordant concentration yielded to the darkest color and improved also the wash fastness properties. The best biomordant in these experiments was oxalic acid, although control samples mordanted with alum yielded to the darkest shades. The obtained colors were deeper in MCC samples than in IC samples. WBE and cellulose-WBE mixtures were exposed to UV radiation and it was observed that the color was gradually darkened and the particle size increased. In addition, a self-standing and self-healing film was noticed to form at the air-liquid interface of WBE solution. The results showed also that WBE acted as crosslinking reagent in low solid content TEMPO-CNF hydrogel production. The characterization of WBE is quite novel and the compounds are very similar, which makes quantitative and qualitative analysis challenging. In the future, optimization of the characterization methods is essential in order to make natural dyeing process more controllable, which could eventually allow to scale-up natural dyeing to industrial level
Tuning the water interactions of cellulose nanofibril hydrogels using willow bark extract
(Elsevier Science Ltd., 2023-10-01) Huynh, Ngoc; Valle-Delgado, Juan José; Fang, Wenwen; Arola, Suvi; Österberg, Monika; Department of Bioproducts and Biosystems; Bioproduct Chemistry
Cellulose nanofibrils (CNFs) are increasingly used as precursors for foams, films and composites, where water interactions are of great importance. In this study, we used willow bark extract (WBE), an underrated natural source of bioactive phenolic compounds, as a plant-based modifier for CNF hydrogels, without compromising their mechanical properties. We found that the introduction of WBE into both native, mechanically fibrillated CNFs and TEMPO-oxidized CNFs increased considerably the storage modulus of the hydrogels and reduced their swelling ratio in water up to 5–7 times. A detailed chemical analysis revealed that WBE is composed of several phenolic compounds in addition to potassium salts. Whereas the salt ions reduced the repulsion between fibrils and created denser CNF networks, the phenolic compounds - which adsorbed readily on the cellulose surfaces - played an important role in assisting the flowability of the hydrogels at high shear strains by reducing the flocculation tendency, often observed in pure and salt-containing CNFs, and contributed to the structural integrity of the CNF network in aqueous environment. Surprisingly, the willow bark extract exhibited hemolysis activity, which highlights the importance of more thorough investigations of biocompatibility of natural materials. WBE shows great potential for managing the water interactions of CNF-based products.

Browsing by Author "Arola, Suvi"

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