Wood Cellulose Research Articles

Turning Wood Autohydrolysate Directly into Food Packing Composite Films with Good Toughness

Bio-based composite films were produced by incorporating wood autohydrolysate (WH), chitosan (CS), and cellulose nanocrystals (CNC). In this work, WH was directly utilized without further purification, and CNC was introduced as the reinforced material to prepare WH-CS-CNC composite films with excellent properties. The effects of CNC on the properties of WH-CS-CNC composite films were investigated by characterizing their structures, mechanical properties, oxygen barrier, and thermal stability properties. The results suggested that CNC could improve tensile strength of the composite films, and the tensile strain at break could be up to 4.7%. Besides, the oxygen permeability of the prepared composite films could be as low as 3.57 cm3/day·m2·kPa, making them suitable for the food packaging materials. These above results showed that the addition of CNC is an effective method to enhance the toughness of composite films. In addition, WH-CS-CNC composite films have great potential in the field of sustainable food packing materials.

Physico-chemical description of titanium dioxide–cellulose nanocomposite formation by microwave radiation with high thermal stability

Titanium dioxide–cellulose nanocomposites were nucleated and grown by decomposition of titanium isopropoxide in ethanol media together with wood cellulose fibers into the microwave-assisted solvothermal (MAS) system; the low temperature and fast formation time of the nanocomposites stand out in this methodology. The MAS method was successfully applied in the synthesis of TiO2 with anatase structure in wood cellulose fibers to produce TiO2–cellulose nanocomposites based on hydrolysis, condensation and subsequent polymerization of titanium nanoparticles on cellulose fibers. Through scanning electron microscope it was possible to confirm nanocomposite formation by impregnation/nucleation/growth of titanium dioxide (TiO2) nanoparticles on the fiber walls. The nanocomposites X-ray powder diffraction showed peaks of crystalline titanium dioxide anatase phase associated to additional cellulose diffraction remarks, as well as the absence of the CaCO3 phase, proving the nanocomposite design concept. This means that the inclusion of TiO2 nanoparticles on fibers does not alter the crystalline structure of cellulose, also confirmed by Fourier-transform mid-infrared spectroscopy. Based on the thermogravimetric analysis, nanocomposites are thermally more stable than pure cellulose, reaching a 19% difference of mass loss reduction.

Improving the thermal stability of wood-based cellulose by esterification

Improvement in the thermal stability of wood-based cellulose; the needle-leaf, bleached, krafp pulp (NBKP) and the wood cellulose nanofibers (WCNF) obtained from the NBKP, was achieved by esterification. Initially, four different types of NBKP esters (acetyl, C2; myristoyl, C14; benzoyl, BNZ; and pivaloyl, PIV) with different degree of substitution (DS) values were prepared to evaluate the effect of esterifying the hemicellulose. The findings revealed that an optimum DS, which possibly completely esterifies the hemicellulose and amorphous cellulose, is needed to achieve significant improvement in thermal stability. Moreover, BNZ and PIV gave higher thermal stability than that of the C2 and C14.BNZ was selected over PIV to modify the WCNF. Benzoylation increased the 1% weight loss temperature (WLT) of WCNF by 25 °C and improved its resistance against thermal weight loss at the early stage of degradation and discoloration. Unlike the results of NBKP, changing the DS from 0.4–1.1 did not show variation in the thermal behavior of WCNF esters. The effect of esterifying the hemicellulose in WCNF was not clearly observed possibly due to the formation of reducing ends brought by mechanical fibrillation during WCNF preparation. Finally, the thermal stability of wood-based celluloses can be comparable to that of highly crystalline and pure bacterial cellulose after benzoylation at an optimum DS.

Towards a multi-scale understanding of dilute hydrochloric acid and mild 1-ethyl-3-methylimidazolium acetate pretreatment for improving enzymatic hydrolysis of poplar wood

Sole pretreatment methods always have limitations in improving enzymatic hydrolysis of wood due to the multi-scale biomass recalcitrance. Herein, dilute acid pretreatment (DAP) with 2% hydrochloric acid at 160 °C and mild ionic liquid pretreatment (MILP) with 1-ethyl-3-methylimidazolium acetate at 90 °C were combined to increase cellulose accessibility in poplar wood. Additionally, the compositional, structural, and topochemical changes of wood during pretreatment and their effect on cellulose digestibility were comprehensively investigated and well understood. The sequential DAP and then MILP led to the highest yield of fermentable sugar (87.15%) after 72 h enzymatic hydrolysis when compared with the sole pretreatments and the sequential MILP and then DAP (21.31–73.64%). We suggested that the significant hemicellulose removal and cell wall deconstruction during first-step DAP exposed more cellulose fibrils to ionic liquid, thereby improving the efficacy of subsequent MILP to delignify wood and change cellulose crystal structure. The considerable removal of both hemicellulose and lignin, the damage of wood structure, and the crystal transformation from cellulose I to cellulose II dramatically improved the enzymatic hydrolysis of the DA + MIL sample. This study provides a better understanding of decomposition mechanism of cell walls during DAP and MILP, which can offer valuable insights into the development of promising pretreatment strategies.

Improvement of enzymatic digestibility of wood by a sequence of optimized milling procedures with final vibratory tube mills for the amorphization of cellulose

AbstractA three-stage wood milling process was investigated leading to coarse, fine and amorphization of milled wood (MW) as a pretreatment for enzymatic wood hydrolysis. An eccentric vibratory tube mill (EVTM) and a spring suspended vibratory tube mill (SSVTM) were found to be suitable for wood cellulose amorphization. Both methods gave rise to highly digestible and amorphous wood powders amenable to enzymatic hydrolysis. The SSVTM had superior energy efficiency. The resulting MW afforded a 70% sugar yield via enzymatic hydrolysis and the total energy consumption was around 1.5 kWh kg−1oven-dried wood (odW) for all three milling stages. In contrast, EVTM consumed 17 kWh kg−1odW energy. Accordingly, SSVTM has a high potential for preparing wood for enzymatic hydrolysis.

Determination of length distribution of TEMPO-oxidized cellulose nanofibrils by field-flow fractionation/multi-angle laser-light scattering analysis

Aqueous nanocellulose dispersions were prepared from wood cellulose by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation. The obtained TEMPO-oxidized cellulose was converted into TEMPO-oxidized cellulose nanofibrils (TOCNs) of different lengths by controlling the nanofibrillation conditions in water or using dilute acid hydrolysis. The average lengths and length distributions of TOCNs have been measured from transmission electron microscopy (TEM) and atomic force microscopy (AFM) images. However, because the number of nanocelluloses observable in TEM and AFM images is limited, a more reliable method is needed to obtain the lengths/length distributions of TOCNs. In this study, the aqueous TOCN dispersions were subjected to a combination of field-flow fractionation (FFF) and multi-angle laser-light scattering (MALLS). The optimum FFF operation conditions for the acid-hydrolyzed TOCN were first established to obtain reasonable data. For TOCNs with average lengths > 400 nm, suitable separation could not be achieved using the FFF/MALLS system. In contrast, the TOCNs with average lengths of 170 and 270 nm were adequately separated according to their sizes by the FFF system. The TOCN length distribution patterns corresponded well to those obtained from TEM images. However, the amounts of TOCNs with lengths > 250 nm were underestimated compared with those determined from TEM images. For TOCNs with average lengths of 170 and 270 nm, the molar mass at each TOCN length was determined using the FFF/MALLS system combined with a refractive index detector, where a specific refractive index increment of 0.165 mL/g was used for TOCN.

High yield production of fungal manganese peroxidases by E. coli through soluble expression, and examination of the activities

Oxidative enzymes of white-rot fungi play a key role in lignin biodegradation. Among those fungus, Ceriporiopsis subvermispora degrades lignin before cellulose in wood; C. subvermispora is the only fungus that secretes all known types of manganese peroxidases (CsMnPs). Utilization of lignin-degrading peroxidases has been limited so far due to the lack of efficient preparation methods and intensive characterization. In this study, we developed a highly efficient method to prepare active CsMnPs through soluble expression by E. coli, which had long been impossible. The genes of MnPs selected from each subfamily were codon-optimized and expressed under the control of a cold shock promoter. A proper level of heme incorporation was achieved by continuous addition of hemin during cultivation. As much as 3 mg of purified MnPs was obtained from 100 mL culture, which is an about 20-fold higher yield than that from inclusion bodies through refolding. Further improvement of the solubility on the expression was achieved by combinatorial coexpression of chaperones. All obtained MnPs had heme-to-protein ratios as high as those of native MnPs. They were all active below pH 5. Our method is applicable to other fungal-secreted enzymes should help the progress of their basic characterization and application for better utilization of woody biomass.

Oxidative pyrolysis of mallee wood biomass, cellulose and lignin

The oxidative pyrolysis of mallee wood, cellulose and lignin was performed and the bio-oil products were analysed to understand how the externally added oxygen react with the pyrolysis products. Both wood cylinders of diameter 8 mm and fine particles (90–300 μm) were pyrolysed in this study to understand the combined effects of biomass particle size and the presence of oxygen. The results revealed that, at a low oxygen concentration, the gas-phase oxidation of volatiles would improve the yields of levoglucosan and syringaldehyde, as well as unsaturated hydroxyl ketones/aldehydes for small wood particles through the oxygen-induced radical reactions. Although oxygen could facilitate the production of some compounds in bio-oil through the gas-phase reactions, it did lead to decreases in the heavy bio-oil yield due to the over-oxidation of some pyrolysis products (e. g. aromatics, lactones, unconjugated alkyl aldehydes/esters and carboxylic acids). The effects of oxygen on the pyrolysis of wood cylinders were more complicated than mallee wood particles due to the secondary reactions of volatiles and the reactions involving the pyrolysing particle surface. The interactions between the polysaccharide-derived and lignin-derived products in gas phase might affect the oxidation of volatiles, changing the formation of pyrolytic products (e.g. levoglucosan and syringaldehyde).

Exothermic effect during torrefaction

There are presented the results of investigation of exothermal effect taking place during torrefaction process. Experiments were carried out with the help of thermoanalyzer SDT Q600, that gives opportunity to use methods of differential thermogravimetric analysis and differential scanning calorimetry, and at the lab-scale installation modelling the column-type torrefaction reactor with indirect (through the wall) heating of processable raw material. It was ascertained the correspondence between the processes of thermal decomposition of basic organic components of wood (hemicellulose, cellulose and lignin) and the characteristic endo- and exothermic peaks on the curve of effective heat capacity. It was shown that the exothermal effect accompanying thermal decomposition of hemicellulose, taking place during torrefaction, may lead to spontaneous heating of wood biomass to temperatures significantly exceeding the wall temperature.

Fabrication of iron oxide nanoparticles, and green catalytic application of an immobilized novel iron Schiff on wood cellulose

In this work, a fabrication route for generating organic–inorganic polymer hybrid materials has been discussed. Natural cellulose was extracted from Sesbania sesban to design a biodegradable microcomposite. A novel iron Schiff base using 2-hydroxy-1-naphthaldehyde as a ligand was immobilized on cellulose along with amin functionality (FeSAC). The structure, morphology and thermal stability of FeSAC were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDAX), FT-IR, Inductively coupled plasma, thermo gravimetric analysis, and elemental analysis. The synthesized catalyst was successfully applied as a green heterogeneous catalyst in the oxidation reaction under a solvent free media and hydrogen peroxide, providing a promising green system for industrial applications. High yield products and selectivities were observed. The longevity of the micro-catalyst was studied and it was found to be reusable for at least six runs. Finally, α-Fe2O3 was obtained by direct calcinations of this biocatalyst at 650 °C within 3 h. α-Fe2O3 nanoparticles were characterized by SEM, high-resolution transmission electron microscopy, and X-ray powder diffraction.

Natural decomposition of hornbeam wood decayed by the white rot fungus Trametes versicolor.

The impacts of white-rot fungi on altering wood chemistry have been studied mostly in vitro. However, in vivo approaches may enable better assessment of the nature of interactions between saprotrophic fungi and host tree in nature. Hence, decayed and sound wood samples were collected from a naturally infected tree (Carpinus betulus L.). Fruiting bodies of the white rot fungus Trametes versicolor grown on the same tree were identified using rDNA ITS sequencing. Chemical compositions (cellulose and lignin) of both sound and infected wood were studied. FT-IR spectroscopy was used to collect spectra of decayed and un-decayed wood samples. The results of chemical compositions indicated that T. versicolor reduced cellulose and lignin in similar quantities. Fungal activities in decayed wood causes serious decline in pH content. The amount of alcohol-benzene soluble extractives was severely decreased, while a remarkable increase was found in 1% sodium hydroxide soluble and hot water extractive contents in the decayed wood samples, respectively. FT-IR analyses demonstrated that T. versicolor causes simultaneous white rot in the hornbeam tree in vivo which is in line with in vitro experiments.

Structural Characterization and Solid State Properties of Thermal Insulating Cellulose Materials of Different Size Classifications

This study investigated two classifications of wood cellulose of particle sizes 300 µm to 424 µm and 600 µm to 849 µm. The cellulose samples were characterized using X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM). The cellulose crystal revealed a preferred orientation along the (200) plane for the most prominent peak. The XRD diffractogram revealed an orthorhombic structure obtained from the powder diffractogram file (PDF). Furthermore, the crystallinity index and crystalline size were calculated and the increase in crystalline size of the isolated cellulose indicated higher thermal stability. The EDX analysis showed chemical components of carbon (C), sodium (Na), chlorine (Cl), and oxygen (O) in the isolated cellulose. The morphology of the cellulose appeared as strings of fibres. The isolated cellulose has applications in the production of biomaterial, thermal insulating devices, and domestic applications.

Changes in the degree of polymerization of wood celluloses during dilute acid hydrolysis and TEMPO-mediated oxidation: Formation mechanism of disordered regions along each cellulose microfibril

Most commercially available plant celluloses, such as kraft pulps and cotton celluloses, have so-called leveling-off degrees of polymerization (LODPs) when subjected to dilute acid hydrolysis. The formation of LODPs is hypothesized to be caused by disordered regions that are present periodically along each cellulose microfibril in plant celluloses. Here, we prepared never-dried wood cellulose, and wood celluloses at different drying stages, and subjected them to dilute acid hydrolysis. The viscosity average degrees of polymerization (DPv) of the wood celluloses decreased in DPv with increasing dilute acid-hydrolysis times. However, the DPv values after 4h of acid hydrolysis differed from those of softwood bleached kraft pulp (SBKP), which showed typical patterns of LODPs. Thus, the disordered regions corresponding to LODPs that were observed for SBKP are probably not synthesized in the native wood. Instead, such disordered regions are formed secondarily or artificially during the isolation/purification and/or drying processes of plant cellulose fibers. The results of the dilute acid hydrolysis and the 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation of SBKP and softwood unbleached soda-anthraquinone pulp showed that the structures of disordered regions can be controlled via the preparation and drying conditions of wood cellulose used as starting materials.

Correlations and adsorption mechanisms of aromatic compounds on biochars produced from various biomass at 700°C.

Knowledge of adsorption behavior of organic contaminants on high heat temperature treated biochars is essential for application of biochars as adsorbents in wastewater treatment and soil remediation. In this study, isotherms of 25 aromatic compounds adsorption on biochars pyrolyzed at 700°C from biomass including wood chips, rice straw, bamboo chips, cellulose, lignin and chitin were investigated to establish correlations between adsorption behavior and physicochemical properties of biochars. Isotherms were well fitted by Polanyi theory-based Dubinin-Ashtakhov (DA) model with three parameters, i.e., adsorption capacity (Q0) and adsorption affinity (E and b). Besides the negative correlation of Q0 with molecular maximum cross-sectional areas (σ) of organic compounds, positive correlations of Q0 with total pore volume (Vtotal) and average diameter of micropore (D) of biochars were observed, indicating that adsorption by biochars is captured by the pore-filling mechanism with molecular sieving effect in biochar pores. Linear solvation energy relationships (LSERs) of adsorption affinity (E) with solvatochromic parameters of organic compounds (i. e., αm and π∗) were established, suggesting that hydrophobic effect, π-π interaction and hydrogen-bonding interaction are the main forces responsible for adsorption. The regression coefficient (π1) and intercept (C) of obtained LSERs are correlated with biochar H/C and Rmicro, respectively, implying that biochars with higher aromaticity and more micropores have stronger π-π bonding potential and hydrophobic effect potential with aromatic molecule, respectively. However, hydrogen-bonding potential of biochars for organic molecules is not changed significantly with properties of biochars. A negative correlation of b with biochar H/C is also obtained. These correlations could be used to predict the adsorption behavior of organic compounds on high heat temperature treated biochars from various biomass for the application of biochars as sorbents and for the estimating of environmental risks of organic compounds in the present of biochars.

Different Conformations of Surface Cellulose Molecules in Native Cellulose Microfibrils Revealed by Layer-by-Layer Peeling.

Layer-by-layer peeling of surface molecules of native cellulose microfibrils was performed using a repeated sequential process of 2,2,6,6-tetramethylpiperidine-1-oxyl radical-mediated oxidation followed by hot alkali extraction. Both highly crystalline algal and tunicate celluloses and low-crystalline cotton and wood celluloses were investigated. Initially, the C6-hydroxy groups of the outermost surface molecules of each algal cellulose microfibril facing the exterior had the gauche-gauche (gg) conformation, whereas those facing the interior had the gauche-trans (gt) conformation. All the other C6-hydroxy groups of the cellulose molecules inside the microfibrils contributing to crystalline cellulose I had the trans-gauche (tg) conformation. After surface peeling, the originally second-layer molecules from the microfibril surface became the outermost surface molecules, and the original tg conformation changed to gg and gt conformations. The plant cellulose microfibrils likely had disordered structures for both the outermost surface and second-layer molecules, as demonstrated using the same layer-by-layer peeling technique.

Modelling Anhydrous Weight Loss of Torrefied Wood Sawdust

Saw mill industries in Malaysia produce a large amount of biomass waste in the form of sawdust, especially from Cengal and Kulim wood species. One of the attractive options to utilize the available biomass is by converting it to an alternative biofuels via torrefaction process. During torrefaction process, biomass is thermally decomposed thus resulted in biomass weight loss which is known as an anhydrous weight loss (AWL). In this study, the kinetic parameters were predicted by two step reactions in series known as Di Blasi – Lanzetta model for both heating and isothermal phases to achieve the desired AWL of torrefied Cengal and Kulim sawdust at temperature of 240°C, 270°C, and 300°C. All kinetic parameters are estimated according to Arrhenius law and fitted to the experimental result. The mass yield results shows that at higher temperature of 300°C, the rate of degradation is higher compared to the lower torrefaction temperature for both Cengal and Kulim woods due to the hemicellulose and cellulose wood constituents. In conclusion, the Di Blasi – Lanzetta model is reliable to predict the AWL of Cengal and Kulim woods in achieving the desired torrefied biomass properties.

Biobased polyurethane foam insulation from microwave liquefaction of woody underbrush

Yaupon holly is one of the most widespread woody underbrush species in the southeastern United States, and it can undermine forest health and safety due to its biofuel-like nature during catastrophic wildfires. Yaupon holly was subjected to microwave liquefaction to produce biobased polyurethane (PU) foam insulation. Liquefaction parameters were optimized and summarized as follows: 1) particle size was controlled in the range of 16- to 40- mesh; 2) both the ratios of glycerol to ethylene glycol and liquid to solid were set at 3:1; 3) the reaction process was conducted at 160 °C for 10 min and catalyzed by 1.5% sulfuric acid. The optimal liquefaction conversion yield was 94.9%. The Fourier transform infrared spectra (FTIR) indicated the successful liquefaction and dissolution of wood essential components, i.e. hemicellulose, cellulose, and lignin. The optimal liquefaction product with solid residue was used directly to produce biofoams. With an increased isocyanate index, the thermal insulation properties, mechanical properties, and thermal stability of biofoams increased. Therefore, a promising biobased PU foam was obtained at an isocyanate index of 150. The density, thermal conductivity, Young’s modulus, and compressive stress of the promising biofoam were 18.5 kg·m-3, 0.033 W·m-1·K-1, 176.7 kPa, and 15.4 kPa, respectively.

The importance of cellulose content and wood density for attack of waterlogged archaeological wood by the shipworm, Teredo navalis

Abstract Archaeological wooden remains are at risk of rapid degradation by the shipworm, Teredo navalis , when exposed to open seawater. An earlier study has shown a difference in the extent of attack based on the state of preservation of the wood. The current study aims to examine in more detail how shipworm attack correlates to the state of preservation, as measured by density, and the amount of residual cellulose, and if it is thereby possible to estimate when attacks will occur based on the level of deterioration. This knowledge would have practical implications for in situ preservation of wooden natural and cultural heritage underwater as it may be able to predict whether a wooden object is in danger of being attacked. The results confirm that there is a significant correlation between the extent of deterioration of the wood and the shipworm attacks. Samples with low density ( 3 ) and a low cellulose content (≤ 24% weight/dry weight) showed no attacks (rating 0). Attacks (rating 1–2) were first observed when the density of the wood was ≥ 134 kg/m 3 , with concomitant cellulose contents of ≥ 29%. Severe attack (rating 3–4) was observed on samples where the density was ≥ 292 kg/m 3 and cellulose contents of ≥ 48%.

Effect of coexisting salt on TEMPO-mediated oxidation of wood cellulose for preparation of nanocellulose

The influence of coexisting salt in 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation of wood cellulose in water at pH 10 for 100 min was investigated, in which Na2SO4 was partly used in place of NaBr in the conventional TEMPO/NaBr/NaClO oxidation system. The amount of NaBr could be reduced from 1 to 0.2 mmol/g-wood cellulose by adding 0.4 mmol/g Na2SO4. This introduced a carboxylate content of ~1.2 mmol/g, which is sufficient to prepare TEMPO-oxidized cellulose nanofibrils (TOCNs) by mechanical disintegration of the oxidized cellulose in water. When no NaBr was used and Na2SO4, Na2SO3, NaCl or CH3COONa was instead used as a coexisting salt in TEMPO/NaClO oxidation, the oxidized celluloses had carboxylate contents of 0.6–0.8 mmol/g, which are insufficient to prepare TOCNs with nanofibrillation yields >55%. The viscosity-average degrees of polymerization of the resulting TEMPO-oxidized celluloses were in the range 420–450, indicating that depolymerization of cellulose is not governed by the carboxylate content of the TEMPO-oxidized cellulose but rather by the oxidation time.

Hydrothermal carbonization for the preparation of hydrochars from glucose, cellulose, chitin, chitosan and wood chips via low-temperature and their characterization

In this work, the hydrothermal carbonization of glucose, cellulose, chitin, chitosan and wood chips at 200°C at processing times between 6 and 48h was studied. The carbonization degree of wood chips, cellulose and chitosan obviously increases as function of time. The heating value of glucose increases to 88% upon carbonization for 48h, while it is only 5% for chitin. It is calculated to be between 44 and 73% for wood chips, chitosan and cellulose. Glucose yielded complete formation of spherical hydrochar structures at a shorter processing time, as low as 12h. However, carbon spheres with narrow size (∼560nm) distribution were obtained upon 48h of residence time. Cellulose and wood chips yielded a similar morphology with an irregular size distribution. Chitin seemed not to undergo hydrothermal carbonization, whereas densely aggregated spheres of a uniform size around 42nm were obtained from chitosan after 18h.