Preparation, Characterization and Application of Amorphized Cellulose—A Review

This review describes the methods of cellulose amorphization, such as dry grinding, mercerization, treatment with liquid ammonia, swelling in solvents, regeneration from solutions, etc. In addition, the main characteristics and applications of amorphized celluloses are discussed. An optimal method for preparing completely amorphous cellulose (CAC) via the treatment of original cellulose material with a cold NaOH/Urea-solvent at the solvent to cellulose ratio R ≥ 5 is proposed. Structural studies show that amorphous cellulose contains mesomorphous clusters with a size of 1.85 nm and specific gravity of 1.49 g/cm3. Furthermore, each such cluster consists of about five glucopyranose layers with an average interlayer spacing of 0.45 nm. Amorphous cellulose is characterized by increased hydrophilicity, reactivity, and enzymatic digestibility. Due to its amorphous structure, the CAC can be used as a promising substrate for enzymatic hydrolysis to produce glucose, which can be applied in biotechnology for growing various microorganisms. In addition, the application of CAC in agriculture is described. A waste-free method for producing amorphous nanocellulose is considered, and the main applications of nanosized amorphous cellulose are discussed.

Degumming of Hemp Fibers Using Combined Microwave Energy and Deep Eutectic Solvent Treatment

Hemp bast fibers were degummed using combined microwave energy (MWE) and deep eutectic solvent (DES) to generate pure hemp cellulose fibers for potential textile applications. The properties of the obtained fibers were investigated and compared with those from the traditional alkali-based process using several analytical techniques. Results revealed that hemp fiber surface underwent dramatic structural disruption during the pretreatment, due to the removal of “gummy” compounds (i.e., lignin, pectin, oil, and wax) and amorphous cellulose. Ultraviolet (UV) protection factor (UPF) of DES-treated fibers with 1:20 fiber-DES ratio (i.e., 183.67) were significantly higher than those from the traditional alkali-treated (140.75) and untreated raw hemp fibers (127.47). The treated fibers also had higher thermal stability. Chemical composition analysis showed that the cellulose content in the treated fiber samples increased to 49.95% which was comparable with the cellulose content of the alkali-treated fibers (49.49%). The study demonstrates a potentially effective, less time-consuming, and environmentally sustainable protocol for manufacturing purified hemp cellulose fibers using combined MWE-DES treatment.

The Optimization of Canola Crop Production through Wheat Residue Management within a Western Canadian Context—A Case Study of Saint-Front, Saskatchewan

In this study, the processes of wheat residue degradation in combination with various tillage treatments were explored to determine the ideal management prescription for maximizing canola crop production. A field experiment within a western Canadian context (near Saint-Front, Saskatchewan), consisting of a 2 × 3 factorial design, was conducted to determine the fate of crop residue under different harvest and treatment scenarios. ATR-Fourier transform infrared (FTIR) spectroscopy, FTIR spectromicroscopy, and synchrotron-based X-ray fluorescence imaging (SR-XFI) were used to explore wheat residue degradation mechanisms. The results indicated maximum canola yields and residue degradation occurred in combination with a combine outfitted with an aftermarket chopper and post-harvest treatment by harrow. Crop residue degradation was attributed to cellulose/linen hydrolysis and supramolecular structure changes from high crystalline to amorphous cellulose. Multi-element loss usually accompanied crop residue degradation. An important aspect of this study is the adoption of field-scale analysis to accurately portray real-world sustainable management techniques within a western Canadian context. The findings provided an optimal combination of crop residue treatment and tillage treatment to increase canola production, which had the potential ability to be applied in other countries. It is also an initial attempt to develop a technical composite of FTIR spectromicroscopy and SR-XFI for examining the mechanism of residue decomposition.

CalkGH9T: A Glycoside Hydrolase Family 9 Enzyme from Clostridium alkalicellulosi

Glycoside hydrolase family 9 (GH9) endoglucanases are important enzymes for cellulose degradation. However, their activity on cellulose is diverse. Here, we cloned and expressed one GH9 enzyme (CalkGH9T) from Clostridium alkalicellulosi in Escherichia coli. CalkGH9T has a modular structure, containing one GH9 catalytic module, two family 3 carbohydrate binding modules, and one type I dockerin domain. CalkGH9T exhibited maximal activity at pH 7.0–8.0 and 55 °C and was resistant to urea and NaCl. It efficiently hydrolyzed carboxymethyl cellulose (CMC) but poorly degraded regenerated amorphous cellulose (RAC). Despite strongly binding to Avicel, CalkGH9T lacked the ability to hydrolyze this substrate. The hydrolysis of CMC by CalkGH9T produced a series of cello-oligomers, with cellotetraose being preferentially released. Similar proportions of soluble and insoluble reducing ends generated by hydrolysis of RAC indicated non-processive activity. Our study extends our knowledge of the molecular mechanism of cellulose hydrolysis by GH9 family endoglucanases with industrial relevance.

Cellulose Nanocomposites of Cellulose Nanofibers and Molecular Coils

All-cellulose nanocomposites have been produced from cellulose nanofiber (CNF) suspensions and molecular coil solutions. Morphology and small-angle neutron scattering studies show the exfoliation and dispersion of CNFs in aqueous suspensions. Cellulose solutions in mixtures of ionic liquid and organic solvents were homogeneously mixed with CNF suspensions and subsequently dried to yield cellulose composites comprising CNF and amorphous cellulose over the entire composition range. Tensile tests show that stiffness and strength quantities of cellulose nanocomposites are the highest value at ca. 20% amorphous cellulose, while their fracture strain and toughness are the lowest. The inclusion of amorphous cellulose in cellulose nanocomposites alters their water uptake capacity, as measured in the ratio of the absorbed water to the cellulose mass, reducing from 37 for the neat CNF to less than 1 for a composite containing 35% or more amorphous cellulose. This study offers new insights into the design and production of all-cellulose nanocomposites.

Moisture uptake in nanocellulose: the effects of relative humidity, temperature and degree of crystallinity

Foams made from cellulose nanomaterials are highly porous and possess excellent mechanical and thermal insulation properties. However, the moisture uptake and hygroscopic properties of these materials need to be better understood for their use in biomedical and bioelectronics applications, in humidity sensing and thermal insulation. In this work, we present a combination of hybrid Grand Canonical Monte Carlo and Molecular Dynamics simulations and experimental measurements to investigate the moisture uptake within nanocellulose foams. To explore the effect of surface modification on moisture uptake we used two types of celluloses, namely TEMPO-oxidized cellulose nanofibrils and carboxymethylated cellulose nanofibrils. We find that the moisture uptake in both the cellulose nanomaterials increases with increasing relative humidity (RH) and decreases with increasing temperature, which is explained using the basic thermodynamic principles. The measured and calculated moisture uptake in amorphous cellulose (for a given RH or temperature) is higher as compared to crystalline cellulose with TEMPO- and CM-modified surfaces. The high water uptake of amorphous cellulose films is related to the formation of water-filled pores with increasing RH. The microscopic insight of water uptake in nanocellulose provided in this study can assist the design and fabrication of high-performance cellulose materials with improved properties for thermal insulation in humid climates or packaging of water sensitive goods. Graphic abstract

The Debye Method is Used to Create 3D Structure Models of Electroactively Transformed Microcrystalline Cellulose

In this paper, we carried out the XRD results and 3D structural models of short-range order of amorphous cellulose obtained by ball milling of microcrystalline cellulose. The amorphous cellulose has the well-reproducible effect of influence of ozone treatment on its proton conductivity, which allows to use this material as a gas sensor. Calculation of the quantitative characteristics of the short-range order (radii of coordination spheres and their dispersions, coordination numbers) of amorphous cellulose was carried out from distribution pair functions curve by using the Finback-Warren method. The space atoms configurations was carried out by Debye method. After that, the models were distorted by converting into packages disoriented relative to each other layers. The X-Ray diffraction patterns were calculated for 3D models and compared with experimental curves.

Ex situ phytoremediation trial of Sardinian mine waste using a pioneer plant species

The mitigation of metals contamination is currently a crucial issue for the reclamation of mine sites. Indeed, mine wastes are often disposed in open dumps and consequently pollutants are subjected to dispersion in the surrounding areas. In this study, the potential use of Helichrysum microphyllum subsp. tyrrhenicum for phytostabilization was evaluated in ex situ conditions. Ninety specimens were randomly selected and were planted in three substrates (reference substrate, mine waste materials, and mine wastes with compost). Mineralogical compositions of substrates, rhizosphere, and roots were assessed through X-ray diffraction (XRD). Zn, Pb, and Cd concentrations of substrates, rhizosphere, soil pore waters, and plant tissues were determined. The phytostabilization potential was determined through the application of biological accumulation coefficient (BAC), biological concentration factor (BCF), and translocation factor (TF). Moreover, survival and biometric parameters were assessed on plant specimens. The polluted substrates and related rhizosphere materials were mainly composed of dolomite, quartz, pyrite, and phyllosilicate. Zn was the most abundant metal in substrates, rhizosphere, and soil pore waters. XRD analysis on roots showed the presence of amorphous cellulose and quartz and Zn was the most abundant metal in plant tissues. H. microphyllum subsp. tyrrhenicum restricts the accumulation of the metals into roots limiting their translocation in aereal parts, indicating its potential use as phytostabilizer (BCF, BAC, TF < 1). Survival and growth data showed a great adaptability to different substrates, with an evident positive effect of the implementation of compost which increased the plant survival and decreased the metals uptake into roots.