Review Analyzing cellulose degree of polymerization and its relevancy to cellulosic ethanol (original) (raw)
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Influence of Cellulose Polymerization Degree and Crystallinity on Kinetics of Cellulose Degradation
Bioresources, 2012
Cellulose was treated in ethylene glycol with p-toluene sulfonic acid monohydrate as a catalyst at different temperatures. At the highest treatment temperature (150 °C) liquefaction of wood pulp cellulose was achieved and was dependant on cellulose polymerization degree (DP). Furthermore, the rate of amorphous cellulose weight loss was found to increase with cellulose degree of polymerization, while the rate of crystalline cellulose weight loss was reciprocal to the size of the crystallites. The cellulose degradation was studied by monitoring of the molecular mass decrease by size-exclusion chromatography. It was revealed that microcrystalline cellulose degrades via a 'quantum mode' mechanism, while the degradation of Whatman filter paper no 1. and cotton linters proceeded randomly and were partly dependent on the starting polymerization degree, crystallinity, and treatment temperature. The kinetics of cellulose degradation in heterogeneous media was described by means of a one-stage model, characterised by the consumption of glycosidic bonds in amorphous and crystalline cellulose regions until the levelling-off degree of polymerization is reached.
Tailoring the Degree of Polymerization of Low Molecular Weight Cellulose
2011
The degradation of cellulose to lmw samples with DP w varying from 15 to 130 is investigated. Cellulose samples prepared from the hydrolysis of regenerated cellulose fibers in dilute HCl possess DP w ¼ 50. Applying homogenous degradation of microcrystalline cellulose in H 3 PO 4 at RT for 3 weeks, samples with DP w ¼ 35 and a PDI of 1.58 are obtained. Decreasing the hydrolysis temperature to 8 8C results in lmw cellulose with DP w > 70. Fractionation in DMA/LiCl provides samples with DP w ¼ 12 to 130, together with a narrow molecular weight distribution. Detailed structural analysis by 2D NMR spectroscopy reveals that the prepared lmw celluloses are suitable as mimics for cellulose.
Cellulose hydrolysis – the role of monocomponent cellulases in crystalline cellulose degradation
2003
Changes in the molecular structure of cellulose during hydrolysis with four recombinant -1,4-glycanases from the cellulolytic bacterium Cellulomonas fimi were assessed and compared in an attempt to elucidate the mechanism of crystalline cellulose degradation. It was apparent that the two endoglucanases, Cel6A and Cel5A, degraded sigmacell cellulose differently; Cel5A liberated more soluble sugars (cellobiose and cellotriose) and significantly altered the molecular weight distribution, while Cel6A had a limited effect on the polymer size and liberated primarily cellobiose and glucose. Additionally, both endoglucanases slightly increased the crystallinity of cellulose. In contrast, the cellobiohydrolases, Cel6B and Cel48A, had no effect on cellulose molecular weight and liberated only cellobiose and cellotriose. However, Cel48A was shown to be effective at reducing the crystallinity of the cellulosic substrate, while Cel6B increased the crystallinity index. Synergistic hydrolysis using combinations of the different enzymes showed that, although the cellulose was extensively hydrolysed, the molecular structure of the substrate was similar to the original material. This phenomenon suggests that the actions of individual monocomponent enzymes are offset by the concurrent modification by the complementing enzymes during synergistic hydrolysis.
Effect of acid-chlorite delignification on cellulose degree of polymerization
Bioresource Technology, 2010
Two types of pure cellulose, Avicel PH-101 and Whatman filter paper, were treated with an acid-chlorite delignification procedure in the presence of varying amounts of incorporated lignin, and the molecular weight distributions and degrees of polymerization (DP) of derivatized cellulose were determined by gel permeation chromatography (GPC). Avicel samples with 0% added lignin showed a DP reduction of nearly 5% during acid-chlorite delignification, compared to a 1% drop in DP with 30% added lignin. Lignin-free filter paper samples showed a DP reduction of nearly 35% after hollocellulose delignification. This drop in DP was reduced to less than 12% for samples which contained 30% lignin. Thus, the presence of lignin in biomass samples minimized the DP reduction of cellulose due to acid catalyzed cleavage during acid-chlorite delignification.
Cellobiose dehydrogenase, an active agent in cellulose depolymerization
Applied and environmental microbiology, 1997
The ability of cellobiose dehydrogenase purified from Phanerochaete chrysosporium to modify a Douglas fir kraft pulp was assessed. Although the addition of cellobiose dehydrogenase alone had little effect, supplementation with cellobiose and iron resulted in a substantial reduction in the degree of polymerization of the pulp cellulose. When the reaction was monitored over time, a progressive depolymerization of the cellulose was apparent with the concomitant production of cellobiono-1,5-lactone. Analysis of the reaction filtrates indicated that glucose and arabinose were the only neutral sugars generated. These sugars are derived from the degradation of the cellobiose rather than resulting from modifications of the pulp. These results suggest that the action of cellobiose dehydrogenase results in the generation of hydroxyl radicals via Fenton's chemistry which subsequently results in the depolymerization of cellulose. This appears to be the mechanism whereby a substantial reduct...
Controlled Depolymerisation of Cellulose to a Given Degree of Polymerisation
Cellulose Chemistry and Technology, 2016
The degree of polymerization of cellulose is very relevant for physical and chemical properties of highly engineered biomaterials. The ability to control the level of depolymerisation to a final specific value opens new opportunities to design cellulose-based nanostructured materials. In this paper, the controlled hydrolysis of cellulose in 0-96% ethanol environment and with nine chosen acids (pKa -10-4.7) was studied in order to tailor the pretreatment of dissolving and kraft pulps for various applications. The acid hydrolysis of cellulose in aqueous environment decreased the viscosityaveraged degree of polymerisation (DPν) and relative cellulose content. However, the addition of small amounts of ethanol preserved the cellulose content nearly at the original level, while decreasing the DPν. Furthermore, when the ethanol concentration increased, the DPν decreased manifoldly. The treatment with strong mineral acids in ethanol environment decreased the DPν by 75-80%, regardless of the...
Biotechnology and Bioengineering, 1995
Chemical treatments similar to those routinely used to extract cellulose from plant biomass caused significant increases in the relative crystallinity index (RCI) of Sigmacell 100 (a commercial cellulose of moderate crystallinity), a s measured by x-ray powder diffraction in both the reflectance and transmittance modes. In general, the largest increases in RCI were observed following higher (rather than lower) temperature treatments. Substantial increases in crystallinity were also observed upon resuspension in water prior t o drying, with higher temperatures again resulting in the greatest increases in RCI. Measurement of the RCls of wetted Sigmacell 100 samples by acid hydrolysis kinetics revealed that most of the increased crystallinity occurred rapidly upon contact with water. In contrast to Sigmacell 100, a cellulose of higher initial crystallinity (the microcrystalline cellulose Sigmacell 50) showed little change in crystallinity following the above treatments. The results provide a partial explanation for the inconsistent relationships reported between cellulose crystallinity and cellulose biodegradation.