Molecular weight distribution and functional group profiles of TEMPO-oxidized lyocell fibers

Characterization of carboxylated cellulose nanofibrils and oligosaccharides from Kraft pulp fibers and their potential elicitor effect on the gene expression of Capsicum annuum

Biomass-derived oligo- and polysaccharides may act as elicitors, i.e., bioactive molecules that trigger plant immune responses. This is particularly important to increase the resistance of plants to abiotic and biotic stresses. In this study, cellulose nanofibrils (CNF) gels were obtained by TEMPO-mediated oxidation of unbleached and bleached kraft pulps. The molecular structures were characterized with ESI and MALDI MS. Analysis of the fine sequences was achieved by MS and MS/MS of the water-soluble oligosaccharides obtained by acid hydrolysis of the CNF gels. The analysis revealed the presence of two families: one corresponding to homoglucuronic acid sequences and the other composed by alternating glucose and glucuronic acid units. The CNF gels, alone or with the addition of the water-soluble oligosaccharides, were tested on Chili pepper (Capsicum annuum). Based on the characterization of the gene expression with Next Generation Sequencing (NGS) of the C. annuum's total messenger RNA, the differences in growth of the C. annuum seeds correlated well with the downregulation of the pathways regulating photosynthesis. A downregulation of the response to abiotic factors was detected, suggesting that these gels would improve the resistance of the C. annuum plants to abiotic stress due to, e.g., water deprivation and cold temperatures.

Carboxylated nanocellulose for wound healing applications - Increase of washing efficiency after chemical pre-treatment and stability of homogenized gels over 10 months

To commercialize a biomedical product as a medical device, reproducibility of production and time-stability are important parameters. Studies of reproducibility are lacking in the literature. Additionally, chemical pre-treatments of wood fibres to produce highly fibrillated cellulose nanofibrils (CNF) seem to be demanding in terms of production efficiency, being a bottleneck for industrial upscaling. In this study, we evaluated the effect of pH on the dewatering time and washing steps of 2,2,6,6-Tetramethylpiperidinyloxy (TEMPO)-mediated oxidized wood fibres when applying 3.8 mmol NaClO/g cellulose. The results indicate that the method does not affect the carboxylation of the nanocelluloses, and levels of approximately 1390 μmol/g were obtained with good reproducibility. The washing time of a Low-pH sample was reduced to 1/5 of the time required for washing a Control sample. Additionally, the stability of the CNF samples was assessed over 10 months and changes were quantified, the most pronounced were the increase of potential residual fibre aggregates, reduction of viscosity and increase of carboxylic acid content. The cytotoxicity and skin irritation potential were not affected by the detected differences between the Control and Low-pH samples. Importantly, the antibacterial effect of the carboxylated CNFs against S. aureus and P. aeruginosa was confirmed.

Progress in research on natural cellulosic fibre modifications by polyelectrolytes

In order to improve the mechanical properties and functionalities of natural cellulosic fibres, this paper first analyzed the characteristics of natural cellulosic fibres and the conventional modification methods of natural cellulosic fibres, and then focused on the polyelectrolytes modified natural cellulosic fibres. The main methods and process parameters of this modification were described in detail; the modification effects of polyelectrolytes on different types of fibres were systematically summarized; the influencing factors on modification of fibres were also discussed in depth; the characterization methods of polyelectrolytes modified fibres were analyzed in detail. Finally, the main application fields of polyelectrolytes modified fibres were systematically summarized.

Analysis of celluloses, plant holocelluloses, and wood pulps by size-exclusion chromatography/multi-angle laser-light scattering

Size-exclusion chromatography with multi-angle laser-light scattering and refractive index detection (SEC/MALLS/RI) provides the number- and weight-average molar masses, molar mass distributions, conformations, and linear/branched structures of polymers. In the case of pure celluloses including highly crystalline tunicate and alga celluloses, and hemicellulose-rich plant holocelluloses, soaking in ethylene diamine (EDA) and subsequent solvent exchange to N,N-dimethylacetamide (DMAc) though methanol is effective for complete dissolution in ∼8% (w/w) LiCl/DMAc. SEC/MALLS/RI analysis can, therefore, be applied to pure celluloses, chemical wood pulps, and plant holocelluloses after dissolution in ∼8% (w/w) LiCl/DMAc, dilution to 1% (w/v) LiCl/DMAc and membrane filtration. All pure celluloses and the high-molar-mass cellulose fractions of hardwood and grass holocelluloses have linear and random-coil conformations and various average molar masses and molar mass distributions depending on the cellulose and holocellulose resources. In contrast, Japanese cedar (i.e., softwood) holocellulose and softwood bleached kraft pulp have alkali-stable cellulose/glucomannan branched structures in the high-molar-mass fractions.

Relationship of Distribution of Carboxy Groups to Molar Mass Distribution of TEMPO-Oxidized Algal, Cotton, and Wood Cellulose Nanofibrils

Distributions of carboxy groups among the molecules in 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibrils (TOCNs) prepared from wood, cotton, and algal celluloses were investigated. Most C6-carboxy groups in TOCNs were esterified with anthracene-methyl (-CH₂C₁₄H₉) groups, showing an ultraviolet light (UV) absorption peak at 365 nm. The anthracene-methylated TOCNs were dissolved in 8% (w/w) lithium chloride/N,N-dimethylacetamide (LiCl/DMAc). After dilution to 1% LiCl/DMAc, the solutions were subjected to size-exclusion chromatography with multiangle laser-light scattering, refractive index, and UV detection. For algal TOCN, C6-carboxy group-rich molecules were present predominantly in the low-molar-mass region, which was consistent with the core-clad cellulose chain packing structures in individual algal cellulose microfibrils and partial depolymerization of the oxidized cellulose molecules. In contrast, wood and cotton TOCNs had almost homogeneous distributions of C6-carboxy groups in all molar mass regions, which could not be explained in terms of the simple core-clad cellulose chain packing structures.

Insights into the effects of γ-irradiation on the microstructure, thermal stability and irradiation-derived degradation components of microcrystalline cellulose (MCC)

The microstructure, thermal stability and irradiated degradation components of microcrystalline cellulose were investigated under ⁶⁰Co γ-irradiation (0–1400 kGy).