A novel enzymatic approach to nanocrystalline cellulose preparation

In this work, conditions for an enzymatic pretreatment prior to NCC isolation from cotton linter were assessed. Different cellulase doses and reaction times were studied within an experimental design and NCC were obtained. At optimal enzymatic conditions (20U, 2 h), a total yield greater than 80% was achieved and the necessary enzymatic treatment time was reduced 90%. Different intensities of enzymatic treatments led to proportional decreases in fiber length and viscosity and also were inversely proportional to the amount of released oligosaccharides. These differences within fibers lead to quantitative differences in NCC: increase in acid hydrolysis yield, reduction of NCC surface charge and crystallinity increase. Benefits produced by enzymatic treatments did not have influence over other NCC characteristics such as their sulfur content (˜1%), size (˜200 nm), zeta potential (˜-50 mV) or degree of polymerization (˜200). Evidence presented in this work would reduce the use of harsh sulfuric acid generating a cleaner stream of profitable oligosaccharidesPostprint (author's final draft

Cellulose oxidation by Laccase-TEMPO treatments

In this work, laccase-TEMPO (Lac-T) treatments were applied to bleached commercial dissolving pulp in order to introduce carbonyl and carboxyl groups, which were found to improve dry and wet strength-related properties. Also the solubility behavior towards xanthate reactions was assessed. The effect of a refining step (R) before the oxidative treatment, the absence or presence of oxygen pressure, TEMPO dose (2 or 8% oven dried pulp) and reaction time (8 or 20 h) were thoroughly examined. Treatments conducted in the presence of oxygen pressure exhibited greater amount of functional groups. Introducing a pre-refining treatment resulted in similar functional groups but higher wet strength was achieved. Specifically, a high W/D strength ratio was observed, indicating that wet strength-related property was satisfactorily developed. Besides the fact that all Lac-T treatments caused severe cellulose degradation, no fiber strength loss was detected. In fact, all oxidized samples presented higher Wet Zero-Span Tensile Strength, mainly in R+ Lac-T (O2) sample, which suggested the formation of hemiacetal linkages between the new introduced aldehyde groups and available free hydroxyl groups resulting from fibrillationPostprint (author's final draft

Political Foundations of Universalistic Care Policy: Comparative Politics of Elderly Care Policy in Japan, the U.S., and Sweden

Two enzyme treatments involving xylanase (X) and laccase (L) were used jointly in an XLE sequence (where E denotes alkaline extraction) to bleach oxygen-delignified eucalyptus kraft pulp in the presence of 1-hydroxybenzotriazol (HBT) as mediator. The results of the XLE sequence were compared with those of an LE sequence. The application conditions for the laccase–mediator system were optimized by using a sequential statistical plan involving three variables (viz., the laccase and mediator doses, and the reaction time) with both sequences. The models used to predict the kappa number and brightness revealed that, once all accessible lignin was removed, the system altered other coloured compounds. The best conditions for the L stage involved a reduced mediator dose (0.5% odp). The xylanase pretreatment increased the accessibility of residual lignin and facilitated removal of hexenuronic acids. For a specific target brightness level of 70% ISO, the X pretreatment can save as much as 30% laccase and 80% mediator while shortening the reaction time by 45%.Peer ReviewedPostprint (published version

Comparative evaluation of the action of two different endoglucanases. Part I: on a fully bleached, commercial acid sulfite dissolving pulp

A fully bleached commercial acid dissolving pulp was treated with two endoglucanases, one obtained from Paenibacillus barcinonensis (B) and the other one produced from Cerrena unicolor (F) with the intention to improve cellulose reactivity and processability in the viscose process. B cellulose was tested under 120 U/g oven dry pulp (odp) and the F cellulase under two conditions, 12 and 60 U/g odp. In addition, a purification stage, consisting in a cold caustic extraction (CCE) of 9 % w/v NaOH, was applied before or after the enzymatic treatment in order to reduce the amount of hemicellulose and improve the action of enzymes. The treated pulps were evaluated in terms of brightness, viscosity, water retention value, fibre morphology, carbohydrate composition, Fock solubility and NMR. In general, results revealed that both endoglucanases improved cellulose reactivity, albeit in a different way; thus, B caused no scissions in the cellulose chain and no significant reduction in fibre length, whereas F strongly decreased viscosity, shortened fibre length and increased considerably the amount of fines. The result of applying two different doses of F cellulase was reflected on Fock solubility and fibre morphology. F60 treatment was found to give the highest value of Fock solubility and the biggest reduction of fibre length. The effect of both endoglucanases on Fock solubility was increased by introducing an earlier CCE stage. Finally, a CCE_B120 pulp with 3 % of hemicellulose and 69 % of Fock solubility was obtainedPostprint (author’s final draft

New strategies to bleach dissolving pulps using enzymatic treatments

A biobleaching sequence was applied to sulphite pulp in order to explore new bleaching possibilities using enzymatic treatments. Therefore, the well-known laccase-mediator system was used with the aim to achieve dissolving pulp characteristics. The enzymatic sequence was compared with a conventional hydrogen peroxide treatment in order to elucidate the effect of a laccase stage (L) for a potential industrial application. The treated pulps showed satisfactory results: high cellulose reactivity, high brightness and low content of hemicellulosesPostprint (published version

Dissolving-grade pulp: a sustainable source for fiber production

The global textile fiber output increased five times from 1975 to 2020. Also, in 2010, the combined demand for man-made and natural fibers was projected to increase by 84% within 20 years. Clothing materials are largely made from cotton or petroleum-based synthetic fibers; both sources, however, have adverse environmental impacts. Thus, cotton requires vast amounts of land, water, fertilizers and pesticides, and synthetic fibers are not biodegradable. This scenario has raised the need for further exploration of cellulose polymers as sustainable sources for the textile industry. Cellulose, the most abundant renewable organic material on earth, is an outstanding polymer that by chemical derivatization or modification can offer a broad range of applications. Dissolving-grade pulp (DGP), which consists of highly pure cellulose, is the most suitable material for manufacturing cellulose derivatives and regenerated fibers. The latter are typically obtained by using the viscose process, which has considerable adverse environmental impacts. Although the textile industry has progressed substantially, further efforts are still needed to make its entire production chain more sustainable. This article provides an in-depth introduction to the potential of fibers with a high cellulose content, known as dissolving-grade pulps. It reviews the properties of DGP, the cooking and purifying methods typically used to obtain it, and the process by which paper-grade pulp can be converted into dissolving-grade pulp. Also, it discusses traditional and recently developed technologies for producing regenerated cellulose fibers. Finally, it examines the potential for recovering cellulose from textile waste as a novel sustainable practice.This publication is part of Project PID2020-114070RB-I00 (CELLECOPROD), funded by MCIN / AEI / 10.13039 / 501100011033. The author Elisabet Quintana is a Serra Húnter Fellow.Peer ReviewedPostprint (published version

Ionic liquid, ultrasound-assisted synthesis of lignin nanoparticles for barrier-enhanced all-cellulose nanocomposite films

The primary purpose of this work was to develop novel all-cellulose nanocomposite (ACNC) films by following a green approach that uses an ionic liquid as solvent and requires no additional reducing agents or stabilizers. In this way, biodegradable, UVblocking ACNC films were obtained by partially dissolving cellulose to entrap lignin nanoparticles (LNP) within. Lignin particles in proportions of 3–7 wt% were modified by sonication in an ionic liquid (IL) to obtain lignin-IL dispersions. The influence of the LNP-IL medium on the chemical, physical, and morphological properties of the resulting nanocomposites was examined, and the properties compared with those of an all-cellulose composite (ACC) film and untreated paper. The TEM technique revealed the formation of unevenly spherical LNPs as small as 5.133 ± 0.003 nm, and XRD spectroscopy a transition from cellulose I to II and an increase in the proportion of non-crystalline cellulose as a result of partial dissolution and regeneration. In addition, SEM images confirmed the deposition of LNPs onto the surface of the regenerated cellulose matrix. The incorporation of LNPs considerably enhanced the UV-blocking, oxygen and water-barrier, biodegradation, antioxidant and antibacterial properties of the films. Moreover, LNPs in proportions of 3 and 5 wt% increased tensile strength, and a proportion of 7 wt% allowed the films to block 97% of light at 280 nm and increased antioxidant activity by 68% relative to the control sample. Interestingly, a 7 wt% LNP content in the films decreased antibacterial activity against Staphylococcus aureus and Escherichia coli by about 42.85% and 63.88%, respectively. The new, multifunctional biocomposite films are suitable for various uses in cellulose-based food packagingThis research received financial support from the PID2020-114070RB-I00 (CELLECOPROD) project [MCIN/AEI/10.13039/501100011033]. The first author, E. Amini, gratefully acknowledges the Universitat Politècnica de Catalunya and Banco Santander for the financial support of her predoctoral grant FPI-UPCPostprint (published version

Promising nanocomposites for food packaging based on cellulose-PCL films reinforced by using ZnO nanoparticles in an ionic liquid

The fact that most composites consist of polluting synthetic materials has prompted a search for biodegradable replacements based on cellulose fibers and polycaprolactone as potential packaging materials. In this work, we developed a green, efficient approach to rendering hydrophobic polycaprolactone (PCL) compatible with hy- drophilic cellulose fibers by using an ionic liquid as a nanowelding agent in the presence of zinc oxide nano- particles (ZnONPs). Transparent biobased nanocomposite films were thus directly obtained by in situ ring- opening polymerization (ROP) of e-caprolactone (CL) monomers onto the dissolved cellulose matrix by using the ionic liquid 1-ethyl-3-methylimidazolium acetate ([EMIM]Ac). [EMIM]Ac and ZnONPs were efficiently catalyzed e-caprolactone ROP under mild conditions. Cellulose-grafted PCL nanocomposite films were obtained by adding variable amounts of CL and ZnONPs to the cellulose matrix. The maximum grafting of 40% was achieved by using 5¦wt% ZnONPs and 70% CL. FTIR spectra confirmed the presence of PCL in the nano- composites. Also, FE-SEM revealed uniform dispersion of ZnONPs and PCL in the regenerated cellulose matrix, and trapping of nanoparticles in nanofibrils after the cellulose matrix was regenerated. X-ray diffraction (XRD) spectra showed a decreased apparent crystallinity and crystallite size. The XRD results also confirmed that the crystal properties of the nanocomposite films and an all-cellulose composite (ACC) were almost identical. The mechanical, barrier and optical properties of the nanocomposite films were significantly better than those of the ACC film by effect of the incorporation of ZnONPs and PCL especially with 5¦wt% ZnONPs and 70% CL). The nanocomposite films exhibited acceptable antioxidant activity and UV-light barrier properties, so they hold promise for used in food packaging. Nanocomposite films are in fact multifunctional materials with the potential for use in cellulose-based food packaging by virtue of their being transparent and bio-based, and possessing very good water vapor and oxygen barrier properties.This publication is part of the PID2020-114070RB-I00 (CELLECO- PROD) project, funded by MCIN/AEI/10.13039/ 501100011033. The first author, E. Amini, gratefully acknowledges the Universitat Politècnica de Catalunya and Banco Santander for the financial support of her predoctoral grant FPI-UPCPostprint (published version

Development of advanced and multifunctional biomaterials from two- or three-dimensional structures of cellulose

Programa de doctorat: Doctorat en Enginyeria Tèxtil i Paperer