•Crosslinked cellulose-chitosan foam (CCLBD) was prepared using a LiBr solution.•CCLBD was stable in acidic regions in spite of a low degree of crosslinking.•CCLBD exhibited an adsorption capacity ...(qmax) of 1548.2 mg/g for Congo red (CR).•The qmax for CR was the highest value among the previously reported adsorbents.•CCLBD is an effective adsorbent for the purification of dye-polluted water.
The adsorption of Congo red (CR) was evaluated using cellulose-chitosan foam crosslinked via dialdehyde cellulose (DAC). DAC-crosslinked cellulose-chitosan foam (CCLBD) was obtained by dissolution/regeneration using a LiBr aqueous solution, followed by crosslinking between chitosan and DAC. CCLBD possessed a three-dimensional structure with 40–200 nm wide pores composed of nanofibrils with a width of 10–20 nm, resulting in a high specific surface area of 230 m2/g. CCLBD was highly stable even acidic conditions in spite of a low crosslinking degree of 10.3%, which induced a slight reduction in the amino groups that interact with CR. CCLBD showed a CR adsorption capacity of 1548.2 mg/g and the adsorption process followed the Sips isotherm and pseudo-second-order models.
The thermal degradation behavior of crystalline cellulose has been investigated using thermogravimetry, differential thermal analysis, and derivative thermogravimetry in a nitrogen atmosphere. Three ...cellulose samples,
Halocynthia, cotton, and commercial microcrystalline cellulose Funacel, were used in this study to analyze the influence on crystallite size. They all belongs to cellulose I
β type and those crystallite sizes calculated from the X-ray diffractometry profiles by Scherrer equation were very different in the order
Halocynthia
>
cotton
>
Funacel. The thermal decomposition of cellulose shifted to higher temperatures with increasing crystallite size. However, activation energies for the thermal degradation were the almost the same among the samples: 159–166
kJ
mol
−1. These results indicated that the crystal structure does not affect the activation energy of the thermal degradation but the crystallite size affects the thermal degradation temperature.
Cellulose, the main component of plant cell walls, is degradable in nature. However, to the best of our knowledge, this is the first report that compares the biodegradability of cellulose fibers with ...different structures in natural waters. River water, brackish water, and seawater were collected from the Kamo River and Osaka Bay, Japan. Biodegradation of cellulose fibers with different structures and crystallinities, ramie, mercerized ramie, and regenerated cellulose fibers in the collected natural water was investigated in the dark at 20 °C for 30 days. The primary and aerobic ultimate biodegradability were evaluated by weight loss and biochemical oxygen demand (BOD) tests, respectively. In the weight-loss test, cellulose fibers were found to be degraded by more than 50% in any natural water within 30 days. However, in the BOD test, biodegradation was diminished, with values of 40%, 20–30%, and 2–10% in river water, brackish water, and seawater, respectively. These results indicate that cellulose fibers are easily degraded into fine fragments, but it is difficult to cause their ultimate decomposition into water and carbon dioxide. Existence of such a tendency in the degree of biodegradation among the cellulose fibers remains unclear. The molecular weight of cellulose fibers in natural water was also measured during their degradation. The degradation behavior in river water and seawater was observed to be different from that in brackish water. The results thus obtained indicate that the microorganisms and enzymes that degrade cellulose fibers differ depending on the natural water, which influences the degree and mechanism of biodegradation.
Cellulose II hydrate was prepared from microcrystalline cellulose (cellulose I)
via its mercerization with 5 N NaOH solution over 1 h at room temperature followed by washing with water. The structure ...of cellulose II hydrate changed to that of cellulose II after drying. Compared with cellulose II, cellulose II hydrate exhibited a slightly (8.5%) expanded structure only along the
1
1
¯
0
direction. The hydrophobic stacking sheets of the cellulose II were conserved in the cellulose II hydrate, and water molecules could be incorporated in the inflated two-chain unit cell of cellulose II hydrate. Enzymatic hydrolysis of cellulose I, cellulose II hydrate, and cellulose II was carried out at 37 °C using solutions comprising a mixture of cellulase and β-glucosidase. The hydrolysis of cellulose II hydrate proceeded much faster than the hydrolysis of the other two substrates, while the saccharification ratio of cellulose II was only slightly higher than that of cellulose I. The alkaline mercerization treatment was also applied to sugarcane bagasse. After its direct mercerization, the cellulose in bagasse was converted from cellulose I to cellulose II hydrate, and then to cellulose II after drying. Similar to in the case of microcrystalline cellulose, the rate of the enzymatic hydrolysis of the mercerized bagasse without drying (cellulose II hydrate) was much faster than the enzymatic hydrolysis of the other two substrates. Thus, the wet forms of cellulose and cellulosic biomass after mercerization, and after hydrolysis with cellulolytic enzymes, afforded superior products with extremely high degradability.
Highly porous and strong cellulose aerogels were prepared by gelation of cellulose from aqueous alkali hydroxide/urea solution, followed by drying with supercritical CO2. Their morphology, pore ...structure, and physical properties were characterized by scanning and transmission electron microscopy, X‐ray diffraction, nitrogen adsorption measurements, UV/Vis spectrometry, and tensile tests. The cellulose hydrogel was composed of interconnected fibrils of about 20 nm wide. By using supercritical CO2 drying, the network structure in the hydrogel was well preserved in the aerogel. The results are preliminary but demonstrate the ability of this method to give cellulose aerogels of large surface areas (400–500 m2 g−1) which may be useful as adsorbents, heat/sound insulators, filters, catalyst supports, or carbon aerogel precursors.
No lightweight when it comes to strength: Highly porous and strong cellulose hydrogels are obtained by dissolution of cellulose in aqueous alkali–urea solution followed by regeneration from various solvents. Drying the hydrogels gives rise to cellulose aerogels (see photo, right) which may be useful, for example, as catalyst supports.
•Biodegradability of cellulose and chitin in natural waters was evaluated.•Cellulose samples with larger specific surface areas were more degradable.•Chitin microcrystals were degraded more than ...cellulose microcrystals.•Degradation was in the order of river water > brackish water > seawater.
This study evaluated the ultimate aerobic biodegradability of cellulose and chitin samples in natural water. The as-prepared cellulose powder, microcrystals, and gel, together with the chitin microcrystals, were observed under an electron microscope and characterized using Fourier transform infrared spectroscopy, X-ray diffraction, and nitrogen-adsorption measurement techniques. The samples were then subjected to biochemical oxygen demand testing at 20 °C, in the dark, for 30 d, in fresh water, brackish water, and seawater collected from the Kamogawa River and Osaka Bay, Japan. The biodegradability of the cellulose and chitin samples was greater than that of the poly(ε-caprolactone) film used as a positive control sample and was in the order of chitin microcrystals > cellulose hydrogel ≈ cellulose microcrystals > cellulose powder. These results indicate that the higher the specific surface area, the higher the degree of degradation of the cellulose samples. Chitin microcrystals displayed a higher degree of degradation than cellulose microcrystals although both had near-identical specific surface areas, indicating that chitin is more easily degraded than cellulose in natural waters. The degree of degradation in natural water was in the order of fresh water > brackish water > seawater. This trend implies that the higher the salinity, the more the degradation was suppressed.
We demonstrated that a unique polysaccharide with extremely high molecular weight can be easily obtained via a low-cost, mild reaction in a water medium from sucrose, a photosynthetic product. ...α-1,3/1,6-Glucosyltransferase L (GtfL) from Streptococcus salivarius produced water-insoluble α-d-glucan from sucrose at 37 °C. Gel permeation chromatography revealed the molecular weight was extremely high; the weight-average molecular weight values were more than 1,000,000 irrespective of the substrate concentration. The Smith degradation of neat glucan and NMR spectroscopic analyses of the acetyl derivative revealed a structure similar to that of a comb-type graft copolymer, α-d-(1 → 3)-graft-(1 → 6)-glucan. The anhydroglucose units (AGUs) in the main-chain backbone are linked by (1 → 3)-glycosidic bonds, whereas a side chain consisting of four AGUs via (1 → 6)-glycosidic bonds alternately extends from C6 of the main chain.
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•In vitro synthesis of an α-d-glucan with α-1,3/1,6-glucosyltransferase L from S. salivarius.•Easily obtainable glucan with extremely high molecular weight under a mild condition.•Comb-like structure composed of (1 → 3)-linked main chain and (1 → 6)-linked side chains
Nitroxy radical catalyzed oxidation with hypochlorite/bromide (TEMPO-mediated oxidation) was performed on a cellulose hydrogel prepared using LiOH/urea solvent. TEMPO oxidation successfully ...introduced carboxyl groups onto the surface of the cellulose hydrogel with retention of the gel structure and its nanoporous property. The equilibrium measurement of Cu2+ adsorption showed favorable interaction with Cu2+ and high maximum adsorption capacity. In addition, over 98% of the adsorbed Cu2+ was recovered using acid treatment, and the subsequent washing allowed the TEMPO-oxidized gels to be used repeatedly. Furthermore, the TEMPO-oxidized cellulose hydrogel showed high adsorption capacity for other toxic metal ions such as Zn2+, Fe3+, Cd2+, and Cs+.
A low temperature alkali pretreatment method was proposed for improving the enzymatic hydrolysis efficiency of lignocellulosic biomass for ethanol production. The effects of the pretreatment on the ...composition, structure and enzymatic digestibility of sweet sorghum bagasse were investigated. The mechanisms involved in the digestibility improvement were discussed with regard to the major factors contributing to the biomass recalcitrance. The pretreatment caused slight glucan loss but significantly reduced the lignin and xylan contents of the bagasse. Changes in cellulose crystal structure occurred under certain treatment conditions. The pretreated bagasse exhibited greatly improved enzymatic digestibility, with 24-h glucan saccharification yield reaching as high as 98% using commercially available cellulase and β-glucosidase. The digestibility improvement was largely attributed to the disruption of the lignin-carbohydrate matrix. The bagasse from a brown midrib (BMR) mutant was more susceptible to the pretreatment than a non-BMR variety tested, and consequently gave higher efficiency of enzymatic hydrolysis.
Fungal cellobiohydrolases act at liquid-solid interfaces. They have the ability to hydrolyze cellulose chains of a crystalline substrate because of their two-domain structure, i.e. cellulose-binding ...domain and catalytic domain, and unique active site architecture. However, the details of the action of the two domains on crystalline cellulose are still unclear. Here, we present real time observations of Trichoderma reesei (Tr) cellobiohydrolase I (Cel7A) molecules sliding on crystalline cellulose, obtained with a high speed atomic force microscope. The average velocity of the sliding movement on crystalline cellulose was 3.5 nm/s, and interestingly, the catalytic domain without the cellulose-binding domain moved with a velocity similar to that of the intact TrCel7A enzyme. However, no sliding of a catalytically inactive enzyme (mutant E212Q) or a variant lacking tryptophan at the entrance of the active site tunnel (mutant W40A) could be detected. This indicates that, besides the hydrolysis of glycosidic bonds, the loading of a cellulose chain into the active site tunnel is also essential for the enzyme movement.
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