Pseudo-Lignin Content Decreased with Hemicellulose and Lignin Removal, Improving Cellulose Accessibility, and Enzymatic Digestibility
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Plant lignocellulose constitutes an abundant and sustainable source of polysaccharides that can be converted into biofuels. However, the enzymatic digestion of native plant cell walls is inefficient, presenting a considerable barrier to cost-effective biofuel production. In addition to the insolubility of cellulose and hemicellulose, the tight association of lignin with these polysaccharides intensifies the problem of cell wall recalcitrance. To determine the extent to which lignin influences the enzymatic digestion of cellulose, specifically in secondary walls that contain the majority of cellulose and lignin in plants, we used a model system consisting of cultured xylem cells from Zinnia elegans. Rather than using purified cell wall substrates or plant tissue, we have applied this system to study cell wall degradation because it predominantly consists of homogeneous populations of single cells exhibiting large deposits of lignocellulose. We depleted lignin in these cells by treating with an oxidative chemical or by inhibiting lignin biosynthesis, and then examined the resulting cellulose digestibility and accessibility using a fluorescent cellulose-binding probe. Following cellulase digestion, we measured a significant decrease in relative cellulose content in lignin-depleted cells, whereas cells with intact lignin remained essentially unaltered. We also observed a significant increase in probe binding after lignin depletion, indicating that decreased lignin levels improve cellulose accessibility. These results indicate that lignin depletion considerably enhances the digestibility of cellulose in the cell wall by increasing the susceptibility of cellulose to enzymatic attack. Although other wall components are likely to contribute, our quantitative study exploits cultured Zinnia xylem cells to demonstrate the dominant influence of lignin on the enzymatic digestion of the cell wall. This system is simple enough for quantitative image analysis, but realistic enough to capture the natural complexity of lignocellulose in the plant cell wall. Consequently, these cells represent a suitable model for analyzing native lignocellulose degradation.
Hemicellulose
Secondary cell wall
Digestion
Enzymatic Hydrolysis
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Plant cell wall polysaccharides are predominant components of fibres. Natural fibres have a wide range of industrial applications, such as in paper and textile industries. Furthermore, their demand for use as bio-composites in building and automotive applications is also increasing. For the various applications, a gain of control over fibre characteristics is important. Inherent fibre characteristics are largely determined by the ratio and interactions of cellulose and hemicelluloses. Two main strategies for bioengineering fibre properties are reviewed: (i) modifying the cellulose/hemicellulose ratio (by biosynthesis or biodegradation of specific polysaccharides), and (ii) interference with cellulose-hemicellulose interactions using carbohydrate-binding modules. These in planta approaches may have the potential of complementing the currently used surface modification approaches for modifying fibre characteristics.
Key words: natural fibre, cellulose, hemicellulose, interactions, cell wall modification, carbohydrate binding module, cellulose synthase
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Abstract Poor dimensional stability restricts the commercial utilization of fast-growing wood. In this study, fast-growing poplar ( Populus cathayana ) was treated by removing hemicellulose with hydrothermal treatment and impregnating alkali lignin via full-cell process, synergistically, for enhanced dimensional stability. After modification, hydroxyl groups were reduced in hemicellulose removed wood (DHC), alkali lignin was observed to fill in the cell lumens of vessels and wood fibers in the impregnated wood (AL) and in the wood modified by hemicellulose removal with alkali lignin impregnation (DHCAL). Compared with untreated wood, the volumetric swelling ratio of DHC and AL decreased by 11 % and 21 % under relative humidity (RH) of 89 %, respectively. The volumetric swelling ratio of DHCAL decreased by over 50 %, indicating a positive synergistic effect. The combination of hemicellulose removal and alkali lignin impregnation treatment improved the dimensional stability of wood significantly by reconstructing wood chemical components with various levels of hygroscopicity. This work could meaningfully contribute to the efficient utilization of fast-growing wood and promote the added value of industrial alkali lignin.
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The contents of hemicellulose,cellulose,acid detergent lignin and coarse cellulose in 31 tobacco samples were determined by Fibertec2010 using quartz sand as filter aid.The results showed that: 1) The relative standard deviations(RSDs) of hemicellulose,cellulose,acid detergent lignin and coarse cellulose contents in tobacco,which were simultaneously detected by 6 analytical columns of Fibertec2010,were 2.82%,1.71%,4.79%,and 1.77%,respectively,and those of 4 repetitive determinations by one column were 1.61%,1.06%,3.72%,and 1.80%.2) For the samples of same cultivar,there were no obvious differences of hemicellulose,cellulose,acid detergent lignin and coarse cellulose contents between different stalk positions.3) The contents of cellulose and coarse cellulose in burley tobacco and reconstituted tobacco were significantly higher than that in flue-cured tobacco.4) The hemicellulose content in high grade cigarettes was higher than that in low grade cigarettes,while the contents of cellulose,acid detergent lignin and coarse cellulose were on the contrary.
Hemicellulose
Stalk
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The key of transforming the straw to chemical materials,like ethanol,is the cellulose and hemicellulose of the crop is saccharified efficiently.In this paper,the conditions of separating cellulose and hemicellulose and acidolysising the cellulose to fermentable sugars were optimized.The result is: after boiling water bath for 14h in 2.5mol·L-1,cellulose and hemicellulose was separated when the solid-to-liquid ratio was 1: 90.The purity of cellulose is 93.73%,and the yield of hemicellulose was 76.96%.If the pure cellulose was hydrolyzed in solution of sulphuric acid for 40min when the content of sulphuric acid was 22% and temperature was 121℃.The hydrolyzing ratio was 98.85%.
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