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To achieve a breakthrough in the application of cold caustic extraction, it is necessary to limit the amount of alkali and to dissolve the hemicelluloses sufficiently. A NaOH/ZnO aqueous solution system was used to separate hemicelluloses from bleached bamboo pulp efficiently and selectively. The NaOH/ZnO process proved to be more successful in the removal of hemicelluloses. Under the conditions of 0.5% ZnO concentration, the NaOH/ZnO aqueous solution system decreased the hemicelluloses content to 4.99%, which was lower than 7.46% of the control sample treated with NaOH alone at the same 7% NaOH concentration. Correspondingly, the NaOH/ZnO system led to an increase in alpha-cellulose content with significantly improved hemicelluloses removal efficiency and selectivity. As a result of the NaOH/ZnO process, a higher degree of polymerization was observed, and the cellulose I structure was always maintained, which provided good benefits for the subsequent utilization of cellulose. [ABSTRACT FROM AUTHOR]

Because of the wide adaptability to samples in various states, UV–vis diffuse reflectance spectroscopy has attracted increasing attention. In the present work, it was firstly used to analyze lignocellulosic biomass material and develop the possible use for rapid detection. Through the analysis of the spectra, it was observed that the extremely pure microcrystalline cellulose, filter paper and purchased xylan have almost no absorption, whereas the chemical pulps, dissolving pulps and extracted hemicellulose with residual trace impurities show a weak absorption in the range from 200 nm to 400 nm. The prominent sensitivity to the trace impurities, such as residual lignin, makes the UV–vis diffuse reflectance spectroscopy a potential tool for the rapid detection of the purity of cellulose and hemicellulose. As for lignin, the spectrum is characterized by a broader strong absorption at 250–280 nm and 280–350 nm, of which the latter is similar to UV absorption spectra. In addition, UV–vis diffuse reflectance spectroscopy can be potentially used in monitoring lignin-like substance formation in the biomass engineering. [ABSTRACT FROM AUTHOR]

In this work, a simple two-stage pretreatment (TSP) was utilized to improve hemicellulose separation and alleviate lignin condensation and therefore facilitate hemicellulose extraction and subsequent kraft pulping. In contrast to single-stage pretreatment, TSP showed a significant improvement for hemicellulose extraction and hemicellulose degradation and provided an almost identical cellulose loss. The hemicellulose separation efficiency was significantly improved using TSP with 60 min first followed by 30 min. More importantly, proper pretreatment is beneficial to the subsequent delignification; extensive pretreatment can retard delignification. [ABSTRACT FROM AUTHOR]

In this work, chemical pulp was used to prepare hazy transparent films, and the effects of hemicellulose content on carboxyl group formation during TEMPO-(2,2,6,6-tetramethylpiperidine-1-oxyl) mediated oxidation, and the properties of the film prepared from the chemical pulp were evaluated. The hemicellulose content exhibited a negligible effect on carboxyl content formation, while prior alkaline extraction significantly enhanced the selective oxidation indicating a substantial increase of carboxyl group. The prior alkaline extraction and TEMPO-mediated oxidation initiated severe hemicellulose removal and fiber swelling, and therefore promoted the subsequent ultrasonic fibrillation. The optical transmittance of the film prepared from the chemical pulp was near-constant at ~ 89%, while the haze increased slightly from 85 to 94%, when the hemicellulose content was increased from 6.7 to 19.2%. Conversely, the presence of hemicellulose significantly impaired the film surface properties, possibly due to the large size of the cellulose fibers. [ABSTRACT FROM AUTHOR]

Abstract: Herein, we studied the effects of pretreatment with glucanase (G), xylanase (X), and their combinations [G/X mixtures or sequential addition (G-X and X-G)] on the efficiency of ionic liquid/water (IL/w)—promoted extraction of hemicelluloses from paper-grade pulp. Mild G pretreatment effectively increased the efficiency and selectivity of hemicellulose removal, whereas severe G pretreatment resulted in high glucose loss and low selectivity. Under optimized conditions, G and X pretreatments achieved similar removal efficiencies, especially in IL/w systems with high water content (25 and 20%), whereas the former was inferior to the latter at low water content (15%). Simultaneous G/X treatment achieved more efficient and selective hemicellulose removal than sequential G-X and X-G treatments, with the former sequence outperforming the latter. Finally, sequential extraction with IL/w-20 and IL/w-15 allowed extremely effective hemicellulose removal, decreasing the xylose content of pulp to 1.5%.Graphical Abstract: [ABSTRACT FROM AUTHOR]

Herein, an ionic liquid/water (IL/w) system was developed to separate hemicelluloses from the chemical pulp with enhanced efficiency by employing xylanase. In the traditional IL/w process, when the water content was in the range 20-15%, the extraction of hemicelluloses was 71–80%. However, the highly efficient hemicelluloses removal was always accompanied with an increased cellulose loss. In this regard, xylanase (X) pretreatment was introduced to facilitate the IL/w process for improving the separation selectivity/efficiency of the hemicelluloses. In the case of the IL/w-20 (water content is 20%) procedure, X 30 (30 mg/g xylanase) pretreatment could increase hemicelluloses removal from 71 to 78%, while the separation selectivity increased from 11.0 to 43.8. Additionally, X pretreatment also reduced IL usage/charge to achieve the same degree of hemicelluloses removal. [ABSTRACT FROM AUTHOR]

To further explore the factors that resist hemicelluloses degradation and release, the chemical composition and molecular weight (MW) in both the interior and exterior portions of the hydrothermally pretreated bamboo substrates were characterized. The chemical composition analysis showed that pretreatment made the lignin tend to accumulate on the exterior surface of the bamboo chips; and therefore gave rise to a large difference of lignin content between exterior and interior. Along with the degradation of hemicelluloses, the difference of hemicelluloses content in both the exterior and interior part became small. On the contrary, the hemicelluloses from the both exterior and interior portions had an invariable MW in the early stage of pretreatment; whereas, the difference of hemicelluloses MW between the exterior and interior part increased with the pretreatment continue, indicating low MW of hemicelluloses in the interior portion. Long time pretreatment promoted increasingly lignin covering on the surface of the chips; the lignin coatings might act as a hydrophobic layer blocking the access of the degraded hemicelluloses. [ABSTRACT FROM AUTHOR]

Enhancing removal of hemicelluloses from cellulosic fibers is of decisive importance for producing high-purity cellulose. In this study, poly(ethylene glycol) (PEG) was added to a cold caustic extraction (CCE) process to promote removal of hemicelluloses from a softwood sulfite dissolving pulp. The content of hemicelluloses was considerably decreased from 11.4 % in the original sample to 5.3 % in the PEG/CCE-treated sample under the studied conditions. This positive result of PEG addition can be explained by (1) improved inward penetration and diffusion of NaOH into the fiber structure and outward diffusion of hemicelluloses from the fiber structure to the bulk phase, and (2) enhanced fiber swelling due to inclusion of PEG in the fiber walls and improved NaOH diffusion. Moreover, the effects of PEG/CCE treatment on the distribution of hemicelluloses in the fiber walls and the molecular weight of the residual hemicelluloses in the resulting pulp were investigated. [ABSTRACT FROM AUTHOR]

Electron beam irradiation (EBI) can degrade lignocellulosic materials and thus be used as a pretreatment method for efficient enzymatic hydrolysis. This research is mainly concerned with the degradation of cellulose and hemicelluloses when bamboo chips are exposed to various doses of EBI. The results show that cellulose degradation occurred continuously but without a gradual drop of the crystalline index with irradiation dose ranging from 0 to 50 kGy; meanwhile, no significant changes were observed in the molecular weight of hemicelluloses. An obvious relationship was found between irradiation dose and cellulose degradation, which could be used to control cellulose degradation by adjusting the EBI dose. Furthermore, the difficulty of cellulose depolymerization [G(s)] in bamboo chips by exposure to EBI was calculated as 0.052 µmol/J. [ABSTRACT FROM AUTHOR]

• The TRO application allows a reduction of NaOH with comparable hemicellulose extraction. • The TRO/CCE procedure can make the cellulose fiber more flexible and more accessible. • The reactivity of dissolving pulp is related to accessibility of cellulose materials. The development of effective separation of hemicelluloses from fully bleached cellulosic pulp fibers is conducive to the development and utilization of high value-added cellulose products. In this study, Turkey Red Oil (sulfonated castor oil) (TRO), a renewable source, was proposed to facilitate hemicelluloses separation from chemical pulp in cold caustic extraction (CCE). As expected, TRO application can significantly promote hemicelluloses separation in the CCE process. By contrast to the traditional CCE process, TRO/CCE could decrease the hemicelluloses content from 9.1 to 6.1%, while the hemicelluloses removal selectivity increased from 72.5 to 82.3% and efficiency, increased from 52.4 to 68.1%. Moreover, without sacrificing hemicelluloses removal, the TRO utilization can reduce the alkaline consumption and therefore preserve the cellulose I crystal from conversion to cellulose II. Additionally, the TRO/CCE procedure made the cellulose fiber more flexible and more accessible to react with CS 2 and therefore a high Fock reactivity. [ABSTRACT FROM AUTHOR]