Browsing by Department "Department of Bioproducts and Biosystems"

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  • 1-Butanol Separation from Aqueous Acetone-Butanol-Ethanol (ABE) Solutions by Freeze Concentration
    (2023-06-07) Osmanbegovic, Nahla; Chandgude, Vijaya; Bankar, Sandip; Louhi-Kultanen, Marjatta
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The suspension freeze crystallization of aqueous 1-butanol solutions, synthetic acetone-butanol-ethanol (ABE) solutions, and ABE fermentation broth was studied as a novel concentration method that requires less energy than evaporation for water removal. The equimolar aqueous ABE solutions in a total molality range of 0–5.05 mol/kg(water) were proven to be ideal solutions based on the freezing point depression obtained. An aqueous solution of 8 wt % 1-butanol and three different types of aqueous ABE solutions (3:8:1:88 ABEW, 6:16:2:76 ABEW, and 10:17:2:71 ABEW (wt %)) were concentrated for 80 min by suspension freeze crystallization in a subcooling range from 0.24 to 1.15 °C. Freeze crystallization enabled 1-butanol separation from the generated mother liquor, which split into two liquid phases after ice separation, i.e., a water-enriched phase and a 1-butanol-enriched phase. Ice yield values were higher for higher subcooling degrees and higher initial water content in the feed solutions. 1-Butanol yields separated from the mother liquors were 9.85%, 59.46%, and 22.46% for 3:8:1:88 ABEW, 6:16:2:76 ABEW, and 10:17:2:71 ABEW, respectively, whereas two-stage freeze crystallization of the fermentation broths resulted in water removal with a maximum relative percentage of 29.5%.
  • 2-Mercaptoimidazolium halides : structural diversity, stability and spontaneous racemisation
    (2020-09-28) Braun, Doris E.; Lampl, Martin; Kahlenberg, Volker; Wurst, Klaus; Schottenberger, Herwig; Hummel, Michael; Griesser, Ulrich J.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Experimental and theoretical characterisation and studies of the stability of heterobicyclic thiazinium salts (bicyclic 2-mercaptoimidazolium chlorides and bromides) were performed to rationalise and understand the influence of the counterion (Cl−↔ Br−) and the replacement of CH by N on crystal packing, the influence of the anion on the moisture and temperature dependent stability, and the racemisation behaviour of the imidazo-thiazinium chloride. Six compounds were synthesised and for five of the compounds the structures were solved from single-crystal X-ray diffraction data. The structural features of the sixth compound could be derived from powder X-ray diffraction data comparisons. An exchange of the Cl−anion by Br−does not influence the crystal packing of the racemic thiazinium salt but increases its moisture dependent stability. In contrast, replacing the imidazole moiety of the cation by a triazole or tetrazole moiety results in distinct packing arrangements of the investigated bromide salts, although,substitution calculations suggest that isostructural packing arrangements might exist. The binary melting point phase diagram was constructed to confirm the nature of the racemic species of the thiazinium chloride, and differential scanning calorimetry and lattice energy minimisations were used to estimate the enthalpy difference between the racemic and enantiopure crystals, rationalising the high tendency of racemisation of the enantiopure compound.
  • 2D Assignment and quantitative analysis of cellulose and oxidized celluloses using solution-state NMR spectroscopy
    (2020-09-01) Koso, Tetyana; Rico del Cerro, Daniel; Heikkinen, Sami; Nypelö, Tiina; Buffiere, Jean; Perea-Buceta, Jesus E.; Potthast, Antje; Rosenau, Thomas; Heikkinen, Harri; Maaheimo, Hannu; Isogai, Akira; Kilpeläinen, Ilkka; King, Alistair W.T.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The limited access to fast and facile general analytical methods for cellulosic and/or biocomposite materials currently stands as one of the main barriers for the progress of these disciplines. To that end, a diverse set of narrow analytical techniques are typically employed that often are time-consuming, costly, and/or not necessarily available on a daily basis for practitioners. Herein, we rigorously demonstrate a general quantitative NMR spectroscopic method for structural determination of crystalline cellulose samples. Our method relies on the use of a readily accessible ionic liquid electrolyte, tetrabutylphosphonium acetate ([P-4444][OAc]):DMSO-d(6), for the direct dissolution of biopolymeric samples. We utilize a series of model compounds and apply now classical (nitroxyl-radical and periodate) oxidation reactions to cellulose samples, to allow for accurate resonance assignment, using 2D NMR. Quantitative heteronuclear single quantum correlation (HSQC) was applied in the analysis of key samples to assess its applicability as a high-resolution technique for following cellulose surface modification. Quantitation using HSQC was possible, but only after applying T(2)correction to integral values. The comprehensive signal assignment of the diverse set of cellulosic species in this study constitutes a blueprint for the direct quantitative structural elucidation of crystalline lignocellulosic, in general, readily available solution-state NMR spectroscopy. [GRAPHICS] .
  • 3D printed manifolds for improved flow management in electrodialysis operation for desalination
    (2021-06-01) Gonzalez-Vogel, Alvaro; Felis-Carrasco, Francisco; Rojas, Orlando J.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Desalination with electrodialysis requires cell designs for optimal flow distribution. Such units include polymeric frames, electrodes, membranes and spacers. Frames are used for mechanical support of electrodes and hydraulic connectors. Their geometry needs to be customized for appropriate fluid management and hydraulic compartmentalization. Typically, such electrodialysis frames are manufactured by drilling solid plastic blocks. However, design flexibility is required to fit the increasing number of developments incorporating new materials and flow inter-connectivity. Here we propose additive manufacturing coupled with computational design to optimize flow dynamics and their coupling with physical devices. First, CAD models are proposed to incorporate major improvements in process lines, and to integrate internal manifold cavities. Even fluid flow and pressure drop distributions are verified by numerical models at given flowrates. The frames were 3D printed and assembled with electrodes and membranes to investigate their performance, and to experimentally confirm numerical predictions. Compared to conventional frames, and as a result of the even distribution of the fluids inside the cell, it was possible to reach an improved (21% higher) limiting current density while ensuring pH stability. Finally, our approach can be integrated in new designs, taking advantage of material selection and geometrical complexity of 3D-printing to add novel functionalities.
  • 3D printing and properties of cellulose nanofibrils-reinforced quince seed mucilage bio-inks
    (2021-12-01) Bani Asadi, Hossein; Teixeira Polez, Roberta; Kimiaei, Erfan; Madani, Zahraalsadat; Rojas Gaona, Orlando; Österberg, Monika; Seppälä, Jukka
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Plant-based hydrogels have attracted great attention in biomedical fields since they are biocompatible and based on natural, sustainable, cost-effective, and widely accessible sources. Here, we introduced new viscoelastic bio-inks composed of quince seed mucilage and cellulose nanofibrils (QSM/CNF) easily extruded into 3D lattice structures through direct ink writing in ambient conditions. The QSM/CNF inks enabled precise control on printing fidelity where CNF endowed objects with shape stability after freeze-drying and with suitable porosity, water uptake capacity, and mechanical strength. The compressive and elastic moduli of samples produced at the highest CNF content were both increased by ~100% (from 5.1 ± 0.2 kPa and 32 ± 1 kPa to 10.7 ± 0.5 and 64 ± 2 kPa, respectively). These values ideally matched those reported for soft tissues; accordingly, the cell compatibility of the printed samples was evaluated against HepG2 cells (human liver cancer). The results confirmed the 3D hydrogels as being non-cytotoxic and suitable to support attachment, survival, and proliferation of the cells. All in all, the newly developed inks allowed sustainable 3D bio-hydrogels fitting the requirements as scaffolds for soft tissue engineering.
  • 3D Printing of Superhydrophobic Objects with Bulk Nanostructure
    (2021-11-11) Dong, Zheqin; Vuckovac, Maja; Cui, Wenjuan; Zhou, Quan; Ras, Robin H.A.; Levkin, Pavel A.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The rapid development of 3D printing (or additive manufacturing) technologies demands new materials with novel properties and functionalities. Superhydrophobic materials, owing to their ultralow water adhesion, self-cleaning, anti-biofouling, or superoleophilic properties are useful for myriad applications involving liquids. However, the majority of the methods for making superhydrophobic surfaces have been based on surface functionalization and coatings, which are challenging to apply to 3D objects. Additionally, these coatings are vulnerable to abrasion due to low mechanical stability and limited thickness. Here, a new materials concept and methodology for 3D printing of superhydrophobic macroscopic objects with bulk nanostructure and almost unlimited geometrical freedom is presented. The method is based on a specific ink composed of hydrophobic (meth)acrylate monomers and porogen solvents, which undergoes phase separation upon photopolymerization to generate inherently nanoporous and superhydrophobic structures. Using a desktop Digital Light Processing printer, superhydrophobic 3D objects with complex shapes are demonstrated, with ultralow and uniform water adhesion measured with scanning droplet adhesion microscopy. It is shown that the 3D-printed objects, owing to their nanoporous structure throughout the entire volume, preserve their superhydrophobicity upon wear damage. Finally, a superhydrophobic 3D-printed gas-permeable and water-repellent microfluidic device and a hierarchically structured 3D-printed super-oil-absorbent are demonstrated.
  • 3D-Printed Thermoset Biocomposites Based on Forest Residues by Delayed Extrusion of Cold Masterbatch (DECMA)
    (2021-10-18) Trifol, Jon; Jayaprakash, Siddharth; Baniasadi, Hossein; Ajdary, Rubina; Kretzschmar, Niklas; Rojas, Orlando J.; Partanen, Jouni; Seppälä, Jukka V.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    We developed a 3D-printing process based on thermoset biocomposites termed Delayed Extrusion of Cold Masterbatch (DECMA). DECMA is a processing method, based on controlling the degree of curing, that takes some responsibility of the 3D printing from materials and as such can be used to 3D print otherwise unprintable materials. First, a masterbatch was produced by mixing a bio-based resin (bioepoxy) and sawdust and lignin. This paste was partially cured at room temperature until reaching an apparent viscosity suitable for extrusion (≈105 mPa·s at 1 s-1). The system was next cooled (5-10 °C) to delay subsequent hardening prior to 3D printing. The printability of the biocomposite paste was systematically investigated and the merits of the delayed extrusion, via DECMA, were assessed. It was found that DECMA allowed the revalorization of sawdust and lignin via 3D printing, as direct printing led to failed prints. Our approach afforded cost-effective, shear-thinning dopes with a high bio-based content (58-71%). The bio-based 3D-printed materials demonstrated good machinability by computer numerical control (CNC). Overall, the benefits of the introduced DECMA method are shown for processing bio-based materials and for on-demand solidification during additive manufacturing.
  • Ability of Poisson-Boltzmann Equation to Capture Molecular Dynamics Predicted Ion Distribution around Polyelectrolytes
    (2017-09) Batys, Piotr; Luukkonen, Sohvi; Sammalkorpi, Maria
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
  • Absorbent Filaments from Cellulose Nanofibril Hydrogels through Continuous Coaxial Wet Spinning
    (2018-08-15) Lundahl, Meri J.; Klar, Ville; Ajdary, Rubina; Norberg, Nicholas; Ago, Mariko; Cunha, Ana Gisela; Rojas, Orlando J.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    A continuous and scalable method for the wet spinning of cellulose nanofibrils (CNFs) is introduced in a core/shell configuration. Control on the interfacial interactions was possible by the choice of the shell material and coagulant, as demonstrated here with guar gum (GG) and cellulose acetate (CA). Upon coagulation in acetone, ethanol, or water, GG and CA formed supporting polymer shells that interacted to different degrees with the CNF core. Coagulation rate was shown to markedly influence the CNF orientation in the filament and, as a result, its mechanical strength. The fastest coagulation noted for the CNF/GG core/shell system in acetone led to an orientation index of ∼0.55 (Herman's orientation parameter of 0.40), Young's modulus of ∼2.1 GPa, a tensile strength of ∼70 MPa, and a tenacity of ∼8 cN/tex. The system that underwent the slowest coagulation rate (CNF/GG in ethanol) displayed a limited CNF orientation but achieved an intermediate level of mechanical resistance, owing to the strong core/shell interfacial affinity. By using CA as the supporting shell, it was possible to spin CNF into filaments with high water absorption capacity (43 g water/g dry filament). This was explained by the fact that water (used as the coagulant for CA) limited the densification of the CNF core structure, yielding filaments with high accessible area and pore density.
  • Accelerated thermostabilization through electron-beam irradiation for the preparation of cellulose-derived carbon fibers
    (2024-01-31) Jang, Minjeong; Fliri, Lukas; Trogen, Mikaela; Choi, Dongcheon; Han, Jeong Heum; Kim, Jungwon; Kim, Sung Kon; Lee, Sungho; Kim, Sung Soo; Hummel, Michael
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The potential of biobased materials like regenerated celluloses as precursors for carbon fibers (CFs) is long known. However, owing to an intrinsic two pathway pyrolysis mechanism of cellulose its carbonization is accompanied with side reactions under generation of volatiles. In practice, this leads to a reduced char yield, results in inferior mechanical properties of the CFs, and requires time-consuming thermostabilization procedures or wet-chemical pretreatments during production. Thus, their market share currently remains low. In ambitions to circumvent these issues, the potential of electron beam irradiation (EBI) as a dry chemical pretreatment for cellulosic CFs was investigated in this study. The conducted chemical analyses showed that high radiation dosages (2 MGy) lead to a strong depolymerization of the cellulose chains down to oligomers, while the fibrous macrostructure was preserved. Minor oxidation reactions were also evident. Thorough thermostabilization experiments under air in the temperature range from 100 °C to 250 °C revealed that reactions caused by EBI treatment alone were insufficient to increase the char yield. Only when the EBI treated precursor fibers are subjected to heating between 200 and 250 °C the char yield increased significantly to 34.4 % compared to 12.1 % for the untreated fiber. Furthermore, the EBI treatment strongly accelerated the reactions during thermostabilization allowing to collect CFs at heating rates of 2 °C/min compared to 0.5 °C/min needed for pristine fibers. Additionally, cellulose-lignin composite fibers were subjected to EBI treatment, proving that this strategy can also be applied to these emerging biobased CF precursors.
  • Accounting for Substrate Interactions in the Measurement of the Dimensions of Cellulose Nanofibrils
    (2019-07) Mattos, Bruno D.; Tardy, Blaise L.; Rojas, Orlando J.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Mechanically fibrillated cellulose nanofibrils (CNFs) have attracted special attention as building blocks for the development of advanced materials and composites. A correlation exists between CNF morphology and the properties of the materials they form. However, this correlation is often evaluated indirectly by process-centered approaches or by accessing a single dimensionality of CNFs adsorbed on solid supports. High-resolution imaging is currently the best approach to describe the morphological features of nanocelluloses; nevertheless, adsorption effects need to be accounted for. For instance, possible deformations of the CNFs arising from capillary forces and interactions with the substrate need to be considered in the determination of their cross-sectional dimensions. By considering soft matter imaging and adsorption effects, we provide evidence of the deformation of CNFs upon casting and drying. We determine a substantial flattening associated with the affinity of CNFs with the substrate corresponding to a highly anisotropic cross-sectional geometry (ellipsoidal) in the dried state. Negative-contrast scanning electron microscopy is also introduced as a new method to assess the dimensions of the CNFs. The images obtained by the latter, a faster imaging method, were correlated with those from atomic force microscopy. The cross-sectional area of the CNF is reconstructed by cross-correlating the widths and heights obtained by the two techniques.
  • Acetylated Nanocellulose for Single-Component Bioinks and Cell Proliferation on 3D-Printed Scaffolds
    (2019-05-22) Ajdary, Rubina; Huan, Siqi; Zanjanizadeh Ezazi, Nazanin; Xiang, Wenchao; Grande, Rafael; Santos, Hélder A.; Rojas, Orlando J.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Nanocellulose has been demonstrated as a suitable material for cell culturing, given its similarity to extracellular matrices. Taking advantage of the shear thinning behavior, nanocellulose suits three-dimensional (3D) printing into scaffolds that support cell attachment and proliferation. Here, we propose aqueous suspensions of acetylated nanocellulose of a low degree of substitution for direct ink writing (DIW). This benefits from the heterogeneous acetylation of precursor cellulosic fibers, which eases their deconstruction and confers the characteristics required for extrusion in DIW. Accordingly, the morphology of related 3D-printed architectures and their performance during drying and rewetting as well as interactions with living cells are compared with those produced from typical unmodified and TEMPO-oxidized nanocelluloses. We find that a significantly lower concentration of acetylated nanofibrils is needed to obtain bioinks of similar performance, affording more porous structures. Together with their high surface charge and axial aspect, acetylated nanocellulose produces dimensionally stable monolithic scaffolds that support drying and rewetting, required for packaging and sterilization. Considering their potential uses in cardiac devices, we discuss the interactions of the scaffolds with cardiac myoblast cells. Attachment, proliferation, and viability for 21 days are demonstrated. Overall, the performance of acetylated nanocellulose bioinks opens the possibility for reliable and scale-up fabrication of scaffolds appropriate for studies on cellular processes and for tissue engineering.
  • Achieving a Superhydrophobic, Moisture, Oil and Gas Barrier Film Using a Regenerated Cellulose–Calcium Carbonate Composite Derived from Paper Components or Waste
    (2022-08-22) Imani, Monireh; Dimic-Misic, Katarina; Kostic, Mirjana; Barac, Nemanja; Janackovic, Djordje; Uskokovic, Petar; Ivanovska, Aleksandra; Lahti, Johanna; Barcelo, Ernest; Gane, Patrick
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    It has been a persistent challenge to develop eco-friendly packaging cellulose film providing the required multiple barrier properties whilst simultaneously contributing to a circular economy. Typically, a cellulosic film made from nanocellulose materials presents severe limitations, such as poor water/moisture resistance and lacking water vapour barrier properties, related primarily to the hydrophilic and hygroscopic nature of cellulose. In this work, alkyl ketene dimer (AKD) and starch, both eco-friendly, non-toxic, cost-effective materials, were used to achieve barrier properties of novel cellulose–calcium carbonate composite films regenerated from paper components, including paper waste, using ionic liquid as solvent. AKD and starch were applied first into the ionic cellulose solution dope mix, and secondly, AKD alone was coated from hot aqueous suspension onto the film surface using a substrate surface precooling technique. The interactions between the AKD and cellulose film were characterised by Fourier-Transform Infrared Spectroscopy (FTIR) and X-ray Diffraction (XRD) showing the formation of a ketone ester structure between AKD and the hydroxyl groups of cellulose. The presence of calcium carbonate particles in the composite was seen to enhance the cellulose crystallinity. The initial high-water vapour and oxygen transmission rates of the untreated base films could be decreased significantly from 2.00 to 0.14 g m−2 d−1, and 3.85 × 102 to 0.45 × 102 cm3 m−2 d−1, respectively. In addition, by applying subsequent heat treatment to the AKD coating, the water contact angle was markedly increased to reach levels of superhydrophobicity (>150°, and roll-off angle < 5°). The resistance to water absorption, grease-permeation, and tensile strength properties were ultimately improved by 41.52%, 95.33%, and 127.33%, respectively, compared with those of an untreated pure cellulose film. The resulting regenerated cellulose–calcium carbonate composite-based film and coating formulation can be considered to provide a future bio-based circular economy barrier film, for example, for the packaging, construction and agriculture industries, to complement or replace oil-based plastics.
  • Acid dissociation of surface bound water on cellulose nanofibrils in aqueous micro nanofibrillated cellulose (MNFC) gel revealed by adsorption of calcium carbonate nanoparticles under the application of ultralow shear
    (2017-08) Liu, Guodong; Maloney, Thaddeus; Dimic-Misic, Katarina; Gane, Patrick
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    At ultralow shear rate (similar to 0.01 s(-1)), acting below the yield stress of the aqueous gel, adsorption of calcium carbonate nanoparticles (<~100 nm) onto cellulose nanofibrils is induced without pigment–pigment preflocculation. Dispersant-free and polyacrylate treated dispersed carbonate particles are compared. Initially, it is seen that the polyacrylate dispersed material does not adsorb, whereas the dispersant-free carbonate adsorbs readily under the controlled ultralow shear conditions. However, repeated cycles of ultralow shear with intermittent periods in the rest state eventually induce the effect as initially seen with the dispersant-free calcium carbonate. The fibril suspension in the bulk is slightly acidic. The addition of buffer to a controlled pH in the case of the dispersant treated particles maintained a similar delay in the onset of adsorption, but adsorption occurred eventually after repeated cycles. During this cycling process, in parallel, the pH gradually drops under repeated cycles of ultralow shear, opposite to expectation, given the buffering capacity of calcium carbonate. The conductivity, in turn, progressively increases slightly at first and then significantly. The action of surface bound water on the nanofibril is considered key to the action of adsorption, and the condition of ultralow shear suggests that the residence time of the particle in contact with the nanofibril, acting under controlled strain against diffusion in the gel, is critical. It is proposed that under these specific conditions the calcium carbonate nanoparticles act as a probe of the nanofibril surface chemistry. The hydrogen bonded water, known to reside at the nanofibril surface, is thus considered the agent in the carbonate-surface interaction, effectively expressing an acid dissociation, and the calcium carbonate nanoparticles act as the probe to reveal it. An important phenomenon associated with this acid dissociation behaviour is that the adsorbed calcium carbonate particles subsequently act to flocculate the otherwise stable cellulose material, leading to release of water held in the aqueous gel matrix structure. This latter effect has major implications for the industrial ease of use of micro and nanofibrillar cellulose at increased solids content. This novel mechanism is also proposed for use to enhance the dewatering capability in general of complex cellulose-containing gel-like water-holding suspensions.
  • Activation of carbon tow electrodes for use in iron aqueous redox systems for electrochemical applications
    (2020-06-21) Schröder, Philipp; Aguiló-Aguayo, Noemí; Auer, Andrea; Grießer, Christoph; Kunze-Liebhaüser, Julia; Ma, Yibo; Hummel, Michael; Obendorf, Dagmar; Bechtold, Thomas
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Excellent chemical inertness, good conductivity and high overpotentials for water electrolysis make carbon fibres (CFS) an ideal electrode material for electrochemical applications. A customized design of three-dimensional (3D) carbon electrodes can be achieved by tailored fibre placement of carbon tows with textile production techniques like embroidery. After manufacturing of the 3D structure, appropriate removal of the polymer coating and oxidative activation is required to achieve low overpotentials and avoid thermal treatments of the carbon structure. For the electrolytes Na[FeIII-racEDDHA] and K4[FeII(CN)6] a sequential treatment by acetone extraction and anodic oxidation was identified to yield optimum surface activation. Electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy of activated fibres indicated complete removal of the coating layer without damage of the CFS. From electrochemical impedance spectroscopy (EIS) at the carbon tow electrodes, charge transfer resistances of <0.1 Ω (0.023 Ω g) and < 0.2 Ω (0.046 Ω g) were determined at 50% state-of-charge (SoC) for 65 mM K4[FeII(CN)6] and 65 mM Na[FeIII-racEDDHA], respectively. In potentiostatic bulk electrolysis no electrode deactivation was observed during 10 charge/discharge cycles (5-6 hours) between 10% and 90% SoC. The processing of carbon tows by textile techniques to near net shaped 3D electrodes opens a new method to manufacture electrodes for electrochemical applications, such as redox flow cells.
  • Activation of softwood Kraft pulp at high solids content by endoglucanase and lytic polysaccharide monooxygenase
    (2021-08) Ceccherini, Sara; Rahikainen, Jenni; Marjamaa, Kaisa; Sawada, Daisuke; Grönqvist, Stina; Maloney, Thaddeus
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The manufacturing of man-made cellulose fibers starts with the dissolution of wood pulp fibers. Pulps can dissolve at different rates and leave different amounts of undissolved particles. Thus, their properties can be modified to achieve better dissolution. Enzymatic treatments are an effective means of enhancing pulp dissolution, and this study compares the effect of endoglucanase (TrCel45A) and lytic polysaccharide monooxygenase (LPMO, TrAA9A) on bleached softwood Kraft pulp at 20 % solids content. The enzymes were applied individually and in combination. Both enzymes increased fibrillation, fines content, porosity, water retention value, crystallinity index and crystallite size, but the largest changes were achieved with the enzyme mixture. For example, fiber saturation point and water retention value increased by 64 and 37 % with TrCel45A, by 27 and 25 % with TrAA9A, and by 73 and 52 % with both TrCel45A and TrAA9A. Pulp reactivity was indirectly assessed by measuring the dissolution time in cupriethylenediamine. The average dissolution time of the reference pulp measured 642 s, while those of the pulps treated with TrCel45A, TrAA9A and their mixture were 399, 473 and 298 s, respectively. The decrease in dissolution time correlated with the increase in fines, fibrillation, porosity, and water retention value.
  • Activation of TEMPO by ClO2 for oxidation of cellulose by hypochlorite — Fundamental and practical aspects of the catalytic system
    (2017-06-30) Pääkkönen, Timo; Pönni, Raili; Dou, Jinze; Nuopponen, Markus; Vuorinen, Tapani
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Bromide-free TEMPO-catalyzed oxidation of the primary alcohols by sodium hypochlorite (NaOCl) does not proceed without a prior activation of the catalyst. Here were demonstrate an immediate in situ activation of the catalyst with an equimolar addition of chlorine dioxide (ClO2) relative to TEMPO. Sodium bromide (NaBr) had a similar role in activating the catalyst although NaBr was needed in excess and the activation took several minutes depending on the dosage of NaBr. The activation method, or the concentration of NaBr, did not affect the bulk oxidation rate. The selectivity of the ClO2 initiated oxidation remained high up to NaOCl addition of 3 mol/kg bleached birch kraft pulp after which additional loss in yield and depolymerization of cellulose were emphasized with negligible increase in carboxylate content. A carboxylate content of 0.8–1 mol/kg, sufficient for easy mechanical fibrillation of the pulp, was achieved under mild conditions with NaOCl addition of 2-2.5 mol/kg pulp.
  • Adaptation of targeted nanocarriers to changing requirements in antimalarial drug delivery
    (2017-02-01) Marques, Joana; Valle-Delgado, Juan José; Urbán, Patricia; Baró, Elisabet; Prohens, Rafel; Mayor, Alfredo; Cisteró, Pau; Delves, Michael; Sinden, Robert E.; Grandfils, Christian; de Paz, José L.; García-Salcedo, José A.; Fernàndez-Busquets, Xavier
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The adaptation of existing antimalarial nanocarriers to new Plasmodium stages, drugs, targeting molecules, or encapsulating structures is a strategy that can provide new nanotechnology-based, cost-efficient therapies against malaria. We have explored the modification of different liposome prototypes that had been developed in our group for the targeted delivery of antimalarial drugs to Plasmodium-infected red blood cells (pRBCs). These new models include: (i) immunoliposome-mediated release of new lipid-based antimalarials; (ii) liposomes targeted to pRBCs with covalently linked heparin to reduce anticoagulation risks; (iii) adaptation of heparin to pRBC targeting of chitosan nanoparticles; (iv) use of heparin for the targeting of Plasmodium stages in the mosquito vector; and (v) use of the non-anticoagulant glycosaminoglycan chondroitin 4-sulfate as a heparin surrogate for pRBC targeting. The results presented indicate that the tuning of existing nanovessels to new malaria-related targets is a valid low-cost alternative to the de novo development of targeted nanosystems.
  • Adaptive Neuro-Fuzzy Inference System to Predict the Release of Microplastic Fibers during Domestic Washing
    (2022-01-01) Muthusamy, Lekha Priya; Periyasamy, Aravin Prince; Militky, Jiri; Thangasamy, Palani Rajan
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Micro plastic particles are a burgeoning population crisis in marine environments. This work is to predict the release of micro plastic fibers from jeans made from polyester during domestic washing by using of adaptive neuro-fuzzy inference system (ANFIS) model. The advantage of the ANFIS model is to predict the variations between the randomly chosen parameters. This prediction model can be cost-effective and slowed down to study behavior more closely. The consequence of washing duration, temperature, spin speed, detergent types, and conditioner usage was investigated against the micro plastic fiber release. The washing temperature, washing duration, spin speed, detergent types, and addition of conditioner are the main factors for this research work. The forecast presentations have been exposed by having a considerably lowered root mean square error value of 3.23 compared with the variant of the experiment as exposed by its standard deviation for the ANFIS version. This ANFIS model will be able to provide a theoretical understanding to enhance and inhibit micro plastic fiber release from jeans.
  • Addition of Ascorbic Acid or Purified Kraft Lignin in Pulp Refining
    (2016-02) Vänskä, Emilia; Vihelä, Tuomas; Johansson, Leena-Sisko; Vuorinen, Tapani
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The effects of two pulp pretreatments, impregnation with ascorbic acid (AA) or purified kraft lignin (KL), on bleached pulp refining were investigated by examining and testing handsheets made from these pulps. The AA pretreatment of the pulp amplified the depolymerization of the cellulose and notably impaired the strength properties of the pulp handsheets. The effects were enhanced upon the combination of the AA pretreatment and intensive refining. Furthermore, heat treatments (at 225 degrees C, 30 min, in water vapor atmospheres of 1 and 75% (v/v)) promoted the depolymerization of cellulose and the total color difference in the AA impregnated handsheets more than for the KL impregnated and reference handsheets. In contrast to AA, the KL pretreatment of the pulp improved the burst index stability of the refined pulp handsheets after the humid thermal treatment (75% (v/v)). In addition, the total color difference of the KL impregnated handsheets was lower than the AA impregnated and reference handsheets.