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1.
Comparative properties of cellulose nano-crystals from native and mercerized cotton fibers 总被引:1,自引:0,他引:1
Yiying Yue Chengjun Zhou Alfred D. French Guan Xia Guangping Han Qingwen Wang Qinglin Wu 《Cellulose (London, England)》2012,19(4):1173-1187
Stable aqueous suspensions of cellulose nano-crystals (CNCs) were fabricated from both native and mercerized cotton fibers by sulfuric acid hydrolysis, followed by high-pressure homogenization. Fourier transform infrared spectrometry and wide-angle X-ray diffraction data showed that the fibers had been transformed from cellulose I (native) to cellulose II (mercerized) crystal structure, and these polymorphs were retained in the nanocrystals, giving CNC-I and CNC-II. Transmission electron microscopy showed rod-like crystal morphology for both types of crystals under the given processing conditions with CNC-II having similar width but reduced length. Freeze-dried agglomerates of CNC-II had a much higher bulk density than that of CNC-I. Thermo-gravimetric analysis showed that CNC-II had better thermal stability. The storage moduli of CNC-II suspensions at all temperatures were substantially larger than those of CNC-I suspensions at the same concentration level. CNC-II suspensions and gels were more stable in response to temperature increases. Films of CNC and Poly(ethylene oxide) were tested. Both CNC-I/PEO and CNC-II/PEO composites showed increased tensile strength and elongation at break compared to pure PEO. However, composites with CNC-II had higher strength and elongation than composites with CNC-I. 相似文献
2.
Turon X Rojas OJ Deinhammer RS 《Langmuir : the ACS journal of surfaces and colloids》2008,24(8):3880-3887
The interactions between films of cellulose and cellulase enzymes were monitored using a quartz crystal microbalance (QCM). Real-time measurements of the coupled contributions of enzyme binding and hydrolytic reactions were fitted to a kinetic model that described closely significant cellulase activities. The proposed model combines simple Boltzmann sigmoidal and 1 - exp expressions. The obtained kinetics parameters were proven to be useful to discriminate the effects of incubation variables and also to perform enzyme screening. Furthermore, it is proposed that the energy dissipation of a film subject to enzymatic hydrolysis brings to light its structural changes. Overall, it is demonstrated that the variations registered in QCM frequency and dissipation of the film are indicative of mass and morphological transformations due to enzyme activities; these include binding phenomena, progressive degradation of the cellulose film, existence of residual, recalcitrant cellulose fragments, and the occurrence of other less apparent changes throughout the course of incubation. 相似文献
3.
Current technology for conversion of biomass to ethanol is an enzyme-based biochemical process. In bioethanol production,
achieving high sugar yield at high solid loading in enzymatic hydrolysis step is important from both technical and economic
viewpoints. Enzymatic hydrolysis of cellulosic substrates is affected by many parameters, including an unexplained behavior
that the glucan digestibility of substrates by cellulase decreased under high solid loadings. A comprehensive study was conducted
to investigate this phenomenon by using Spezyme CP and Avicel as model cellulase and cellulose substrate, respectively. The
hydrolytic properties of the cellulase under different substrate concentrations at a fixed enzyme-to-substrate ratio were
characterized. The results indicate that decreased sugar yield is neither due to the loss of enzyme activity at a high substrate
concentration nor due to the higher end-product inhibition. The cellulase adsorption kinetics and isotherm studies indicated
that a decline in the binding capacity of cellulase may explain the long-observed but little-understood phenomenon of a lower
substrate digestibility with increased substrate concentration. The mechanism how the enzyme adsorption properties changed
at high substrate concentration was also discussed in the context of exploring the improvement of the cellulase-binding capacity
at high substrate loading. 相似文献
4.
Kotiranta P Karlsson J Siika-Aho M Medve J Viikari L Tjerneld F Tenkanen M 《Applied biochemistry and biotechnology》1999,82(2):81-90
The adsorption and the hydrolytic action of purified cellulases of Trichoderma reesei, namely, cellobiohydrolase I (CBH I), endoglucanase II (EG II), and their core proteins, on steam-pretreated willow were
compared. The two enzymes differed clearly in their adsorption and hydrolytic behavior. CBH I required the cellulose-binding
domain (CBD) for efficient adsorption and hydrolysis, whereas EG II was able to adsorb to steam pretreated willow without
its CBD. Absence of the CBD decreased the hydrolysis of cellulose by EG II, but the decrease was less pronounced than with
CBH I. A linear relationship was observed between the amount of enzyme adsorbed and the degree of hydrolysis of cellulose
only for CBHI. EG II and EG II core appeared to be able to hydrolyze only 1 to 2% of the substrate regardless of the amount
of protein adsorbed. 相似文献
5.
Adam Elliston Samuel R. A. Collins Craig B. Faulds Ian N. Roberts Keith W. Waldron 《Applied biochemistry and biotechnology》2014,172(7):3621-3634
Waste copier paper is a potential substrate for the production of glucose relevant for manufacture of platform chemicals and intermediates, being composed of 51 % glucan. The yield and concentration of glucose arising from the enzymatic saccharification of solid ink-free copier paper as cellulosic substrate was studied using a range of commercial cellulase preparations. The results show that in all cellulase preparations examined, maximum hydrolysis was only achieved with the addition of beta-glucosidase, despite its presence in the enzyme mixtures. With the use of Accellerase® (cellulase), high substrate loading decreased conversion yield. However, this was overcome if the enzyme was added between 12.5 and 20 FPU g substrate?1. Furthermore, this reaction condition facilitated continual stirring and enabled sequential additions (up to 50 % w/v) of paper to be made to the hydrolysis reaction, degrading nearly all (99 %) of the cellulose fibres and increasing the final concentration of glucose whilst simultaneously making high substrate concentrations achievable. Under optimal conditions (50 °C, pH 5.0, 72 h), digestions facilitate the production of glucose to much improved concentrations of up to 1.33 mol l?1. 相似文献
6.
Hui Wang Kazuhiro Mochidzuki Shinichi Kobayashi Hatsue Hiraide Xiaofen Wang Zongjun Cui 《Applied biochemistry and biotechnology》2013,170(3):541-551
Bovine serum albumin (BSA) was added to filter paper during the hydrolysis of cellulase. Adding BSA before the addition of the cellulase enhances enzyme activity in the solution, thereby increasing the conversion rate of cellulose. After 48 h of BSA treatment, the BSA adsorption quantities are 3.3, 4.6, 7.8, 17.2, and 28.3 mg/g substrate, each with different initial BSA concentration treatments at 50 °C; in addition, more cellulase was adsorbed onto the filter paper at 50 °C compared with 35 °C. After 48 h of hydrolysis, the free-enzyme activity could not be measured without the BSA treatment, whereas the remaining activity of the filter paper activity was approximately 41 % when treated with 1.0 mg/mL BSA. Even after 96 h of hydrolysis, 25 % still remained. Meanwhile, after 48 h of incubation without substrate, the remaining enzyme activities were increased 20.7 % (from 43.7 to 52.7 %) and 94.8 % (from 23.3 to 45.5 %) at 35 and 50 °C, respectively. Moreover, the effect of the BSA was more obvious at 35 °C compared with 50 °C. When using 15 filter paper cellulase units per gram substrate cellulase loading at 50 °C, the cellulose conversion was increased from 75 % (without BSA treatment) to ≥90 % when using BSA dosages between 0.1 and 1.5 mg/mL. Overall, these results suggest that there are promising strategies for BSA treatment in the reduction of enzyme requirements during the hydrolysis of cellulose. 相似文献
7.
Ahola S Turon X Osterberg M Laine J Rojas OJ 《Langmuir : the ACS journal of surfaces and colloids》2008,24(20):11592-11599
Model films of native cellulose nanofibrils, which contain both crystalline cellulose I and amorphous domains, were used to investigate the dynamics and activities of cellulase enzymes. The enzyme binding and degradation of nanofibril films were compared with those for other films of cellulose, namely, Langmuir-Schaefer and spin-coated regenerated cellulose, as well as cellulose nanocrystal cast films. Quartz crystal microbalance with dissipation (QCM-D) was used to monitor the changes in frequency and energy dissipation during incubation at varying enzyme concentrations and experimental temperatures. Structural and morphological changes of the cellulose films upon incubation with enzymes were evaluated by using atomic force microscopy. The QCM-D results revealed that the rate of enzymatic degradation of the nanofibril films was much faster compared to the other types of cellulosic films. Higher enzyme loads did not dramatically increase the already fast degradation rate. Real-time measurements of the coupled contributions of enzyme binding and hydrolytic reactions were fitted to an empirical model that closely described the cellulase activities. The hydrolytic potential of the cellulase mixture was found to be considerably affected by the nature of the substrates, especially their crystallinity and morphology. The implications of these observations are discussed in this report. 相似文献
8.
Caoxing Huang Juan He Douyong Min Chenhuan Lai Qiang Yong 《Applied biochemistry and biotechnology》2016,180(8):1508-1523
In this work, to elucidate why the acid-pretreated bamboo shows disappointingly low enzymatic digestibility comparing to the alkali-pretreated bamboo, residual lignins in acid-pretreated and kraft pulped bamboo were isolated and analyzed by adsorption isotherm to evaluate their extents of nonproductive enzyme adsorption. Meanwhile, physicochemical properties of the isolated lignins were analyzed and a relationship was established with non-productive adsorption. Results showed that the adsorption affinity and binding strength of cellulase on acid-pretreated bamboo lignin (MWLa) was significantly higher than that on residual lignin in pulped bamboo (MWLp). The maximum adsorption capacity of cellulase on MWLp was 129.49 mg/g lignin, which was lower than that on MWLa (160.25 mg/g lignin). When isolated lignins were added into the Avicel hydrolysis solution, the inhibitory effect on enzymatic hydrolysis efficiency of MWLa was found to be considerably stronger than that with MWLp. The cellulase adsorption on isolated lignins was correlated positively with hydrophobicity, phenolic hydroxyl group, and degree of condensation but negatively with surface charges and aliphatic hydroxyl group. These results suggest that the higher nonproductive cellulase adsorption and physicochemical properties of residual lignin in acid-pretreated bamboo may be responsible for its disappointingly low enzymatic digestibility. 相似文献
9.
Yoshihiko Amano Kouichi Nozaki Takashi Araki Hideki Shibasaki Shigenori Kuga Takahisa Kanda 《Cellulose (London, England)》2001,8(4):267-274
We have investigated the reactivities of various cellulases onribbon-type bacterial cellulose (BC I) and band-shaped bacterial cellulose (BCII) so as to clarify the properties of different cellulases. BC I waseffectively hydrolyzed by exo-type cellulases from different fungi from twicetofour times as much as BC II, but endo-type cellulases showed little differencein reactivity on those substrates. One of the endo-type cellulases, EG II fromTrichoderma reesei, degraded BC II more rapidly thanexo-type cellulases even in the production of reducing sugars. The degree ofpolymerization (DP) of BC II was rapidly decreased by endo-type cellulases atanearly stage, while exo-type cellulases did not cause the decrease of DP atthe initial stage, though the decrease of DP was observed after an incubation of24 h. All exo-type cellulases adsorbed on BC I and BC II,whileendo-type cellulases except for EG II adsorbed slightly on both substrates. Itwas interesting to observe EG II adsorbed on BC I but not on BC II. It issuggested that the adsorption of enzyme on cellulose is important for thedegradation of BC I, but not for BC II. It is proposed that the ratio of aspecific activity of each enzyme between BC I and BC II represents thedifference in the mode of action of cellulase. Furthermore, the K
RW value, which we can calculate from thedecrease of DP/reducing sugar produced, is effective for discriminating themode of action of cellulase, especially the evaluation of randomness in thehydrolysis of cellulose by endo- and exo-type cellulases. 相似文献
10.
Thomas Ganner Timothy Aschl Manuel Eibinger Patricia Bubner Arno Meingast Boril Chernev Claudia Mayrhofer Bernd Nidetzky Harald Plank 《Cellulose (London, England)》2014,21(6):3927-3939
Atomic force microscopy in liquid environments (L-AFM) became a state of the art technique in the field of enzymatic cellulose degradation due to its capability of in situ investigations on enzymatic relevant scales. Current investigations are however limited to few substrates like valonia cellulose, cotton linters and processed amorphous cellulose as only these show required flatness and purity. Structurally monophasic, these substrates confine conclusions regarding enzymatic degradation of mixed amorphous–crystalline substrates as commonly found in nature. To exploit the full potential of the technique, cellulose substrates with multiphase properties, flat topology and purity are therefore absolutely required. In this study we introduce a special preparation route based on highly crystalline Avicel PH101® cellulose and the ionic liquid 1-butyl-3-methylimmidazolium chloride as dissolution reagent. As comprehensively shown by atomic force microscopy, wide angle X-ray scattering, Raman spectroscopy and electron microscopy, the developed material allows precise control of its polymorphic composition by means of cellulose types I and II embedded in an amorphous matrix. Together with the tunable composition and flat topology over large areas (>10 × 10 µm2) the material is highly suited for L-AFM studies. 相似文献
11.
Ingrid C. Hoeger Sandeep S. Nair Arthur J. Ragauskas Yulin Deng Orlando J. Rojas J. Y. Zhu 《Cellulose (London, England)》2013,20(2):807-818
Laboratory mechanical softwood pulps (MSP) and commercial bleached softwood kraft pulps (BSKP) were mechanically fibrillated by stone grinding with a SuperMassColloider®. The extent of fibrillation was evaluated by SEM imaging, water retention value (WRV) and cellulase adsorption. Both lignin content and mechanical treatment significantly affected deconstruction and enzymatic saccharification of fibrillated MSP and BSKP. Fibrillation of MSP and BSKP cell walls occurs rapidly and then levels off; further fibrillation has only limited effect on cell wall breakdown as measured by water retention value and cellulase adsorption. Complete (100 %) saccharification can be achieved at cellulase loading of 5 FPU/g glucan for BSKP after only 15 min fibrillation with energy input of 0.69 MJ/kg. However, the presence of lignin in MSP affects the extent of fibrillation producing fibrils mainly above 1 μm. Lignin binds nonproductively to cellulases and blocks cellulose thereby reducing its accessibility. As a result, the cellulose saccharification efficiency of MSP fibrils (6 h of fibrillation, energy input of 13.33 MJ/kg) was only 55 % at same cellulase loading of 5 FPU/g glucan. 相似文献
12.
Kayoko Kobayashi Satoshi Kimura Ung-Jin Kim Ken Tokuyasu Masahisa Wada 《Cellulose (London, England)》2012,19(3):967-974
We prepared two cellulose hydrates, Na-cellulose IV and cellulose II hydrate, along with their respective anhydrous forms,
cellulose II and II′, from microcrystalline cellulose. X-ray diffractometry analysis showed that the structure of the hydrophobic
stacking sheet was conserved in the samples, but the distance between the sheets was in the order: cellulose II hydrate > Na-cellulose
IV > cellulose II and II′. The hydrates exhibited an expanded structure compared with the anhydrous form from the incorporation
of hydrate water, and cellulose II hydrate contained more hydrate water than Na-cellulose IV. Enzymatic hydrolysis of the
samples was carried out at 37 °C using solutions comprising a mixture of cellulase and β-glucosidase. The hydrates were hydrolyzed
more efficiently than the anhydrous forms, and cellulose II hydrate showed a more efficient hydrolysis than Na-cellulose IV.
This result also agrees well with the enzymatic adsorption properties of each sample, where the samples that adsorbed the
greater amount of enzyme showed a higher degradability. The results obtained in this study provide useful knowledge on controlling
the biodegradability of cellulose by converting its structure. 相似文献
13.
In this study, sugarcane bagasse was pretreated with ammonium hydroxide, and the effectiveness of the pretreatment on enzyme hydrolysis and ethanol production was examined. Bagasse was soaked in ammonium hydroxide and water at a ratio of 1:0.5:8 for 0–4 days at 70 °C. Approximately, 14–45 % lignin, 2–6 % cellulose, and 13–22 % hemicellulose were removed during a 0.5- to 4-day ammonia soaking period. The highest glucan conversion of sugarcane bagasse soaked in dilute ammonia at moderate temperature by cellulase was accomplished at 78 % with 75 % of the theoretical ethanol yield. Under the same conditions, untreated bagasse resulted in a cellulose digestibility of 29 and 27 % of the theoretical ethanol yield. The increased enzymatic digestibility and ethanol yields after dilute ammonia pretreatment was related to a combined effect of the removal of lignin and increase in the surface area of fibers. 相似文献
14.
Zheng Y Pan Z Zhang R Wang D Jenkins B 《Applied biochemistry and biotechnology》2008,146(1-3):231-248
Our previous research has shown that saline Creeping Wild Ryegrass (CWR), Leymus triticoides, has a great potential to be used for bioethanol production because of its high fermentable sugar yield, up to 85% cellulose
conversion of pretreated CWR. However, the high cost of enzyme is still one of the obstacles making large-scale lignocellulosic
bioethanol production economically difficult. It is desirable to use reduced enzyme loading to produce fermentable sugars
with high yield and low cost. To reduce the enzyme loading, the effect of addition of non-ionic surfactants and non-catalytic
protein on the enzymatic hydrolysis of pretreated CWR was investigated in this study. Tween 20, Tween 80, and bovine serum
albumin (BSA) were used as additives to improve the enzymatic hydrolysis of dilute sulfuric-acid-pretreated CWR. Under the
loading of 0.1 g additives/g dry solid, Tween 20 was the most effective additive, followed by Tween 80 and BSA. With the addition
of Tween 20 mixed with cellulase loading of 15 FPU/g cellulose, the cellulose conversion increased 14% (from 75 to 89%), which
was similar to that with cellulase loading of 30 FPU/g cellulose and without additive addition. The results of cellulase and
BSA adsorption on the Avicel PH101, pretreated CWR, and lignaceous residue of pretreated CWR support the theory that the primary
mechanism behind the additives is prevention of non-productive adsorption of enzymes on lignaceous material of pretreated
CWR. The addition of additives could be a promising technology to improve the enzymatic hydrolysis by reducing the enzyme
activity loss caused by non-productive adsorption. 相似文献
15.
Yoshiki Horikawa Naoya Konakahara Tomoya Imai Abe Kentaro Yoshinori Kobayashi Junji Sugiyama 《Polymer Degradation and Stability》2013
The enzymatic hydrolysis of cellulose I achieves almost complete digestion when sufficient enzyme loading as much as 20 mg/g-substrate is applied. However, the yield of digestion reaches the limit when the enzyme dosage is decreased to 2 mg/g-substrate. Therefore, we have performed three pretreatments such as mercerization, dissolution into phosphoric acid and EDA treatment. Transformation into cellulose II hydrate by mercerization and dissolution into phosphoric acid were not sufficient because substrate changed to highly crystalline structure during saccharification. On the other hand, in the case of crystalline conversion of cellulose I to IIII by EDA, almost perfect digestion was achieved even in enzyme loading as small as 0.5 mg/g-substrate, furthermore, hydrolyzed residue was typical cellulose I. The structural analysis of substrate after saccharification provides an insight into relationships between cellulose crystalline property and cellulase toward better enzymatic digestion. 相似文献
16.
Diana Ciolacu Selestina Gorgieva Daniel Tampu Vanja Kokol 《Cellulose (London, England)》2011,18(6):1527-1541
This paper investigates the enzymatic hydrolysis of three main allomorphic forms of microcrystalline cellulose using different
cellulases, from Trichoderma reesei and from Aspergillus niger, respectively. It was demonstrated that both the morphological and crystalline structures are important parameters that have
a great influence on the course of the hydrolysis process. The efficiency of the enzymatic hydrolysis of cellulosic substrates
was estimated by the amounts of reducing sugar and by the yield of the reaction. Changes in the average particle sizes of
the cellulose allomorphs were determined during enzymatic hydrolysis. The accumulation of soluble sugar within the supernatant
was used as a measure of the biodegradation process’s efficiency, and was established by HPLC-SEC analysis. Any modifications
in the supramolecular structure of the cellulosic residues resulting from the enzymatic hydrolysis were determined by X-ray
diffraction. The action of each cellulase was demonstrated by a reduction in the crystalline index and the crystallite dimensions
of the corresponding allomorphic forms. The crystalline structure of allomorphic forms I and II did not suffer significant
modifications, while cellulose III recorded a partial return to the crystalline structure of cellulose I. The microstructures
of cellulose allomorph residues were presented using optical microscopy and scanning electron microscopy. 相似文献
17.
Cascade Enzymatic Hydrolysis Coupling with Ultra ne Grinding Pretreatment for Sugarcane Bagasse Sacchari cation 下载免费PDF全文
Zheng-qiu Yuan Jin-xing Long Tie-jun Wang Yu-qin Li Qi Zhang Long-long Ma 《化学物理学报(中文版)》2015,28(3):355-360
The biorefinery process for sugarcane bagasse saccharification generally requires significant accessibility of cellulose. We reported a novel method of cascade cellulase enzymatic hydrolysis coupling with ultrafine grinding pretreatment for sugarcane bagasse saccharification. Three enzymatic hydrolysis modes including single cellulase enzymatic hydrolysis, mixed cellulase enzymatic hydrolysis, and cascade cellulase enzymatic hydrolysis were compared. The changes on the functional group and surface morphology of bagasse during cascade cellulase enzymatic hydrolysis were also examined by FT-IR and SEM respectively. The results showed that cascade enzymatic hydrolysis was the most efficient way to enhance the sugarcane bagasse sacchari cation. More than 65% of reducing sugar yield with 90.1% of glucose selectivity was achieved at 50 oC, pH=4.8 for 72 h (1200 r/min) with cellulase I of 7.5 FPU/g substrate and cellulase II of 5 FPU/g substrate. 相似文献
18.
Xiao Wang Kena Li Ming Yang Jingfeng Wang Junhua Zhang 《Cellulose (London, England)》2017,24(1):35-47
During the pretreatment of lignocellulosic materials, the dissolved mannan would re-adsorb on cellulose, and then inhibited the cellulose hydrolysis by cellulases. However, the adsorption of mannan on cellulose and hydrolyzability of mannan adsorbed on cellulose were not so clear. In this work, the adsorption behavior of mannans on cellulose and the hydrolysis of adsorbed mannan by mannanase were investigated. Adsorption of 1, 4-β-D-mannan (mannan), Konjac glucomannan (GM), and Carob galactomannan (GalM) on Avicel and corn stover (CS) was increased with mannan loading. The adsorbed amount of mannan (94.4 mg/g Avicel and 85.1 mg/g CS) on cellulosic substrates at the mannan concentration of 5 mg/mL was significantly higher (p < 0.05) than that of GM (65.7 mg/g Avicel and 63.7 mg/g CS) and GalM (44.3 mg/g Avicel and 48.7 mg/g CS). Furthermore, the NMR spectra and molecular weight analysis showed that mannan with less side groups and low molecular weight might increase the adsorption. Mannan, GM, and GalM adsorbed on Avicel and CS, which was used as Avicel/CS -mannan/GM/GalM complex, could be hydrolyzed by mannanase, and the hydrolyzability of Avicel-mannan/GalM complexes was stronger than that of Avicel-GM complex. Similarly, the reducing sugars increased by 23.2 and 54.2 % for Avicel-mannan and Avicel-GalM complexes after 48 h hydrolysis by cellulase and mannanase, respectively. The results suggested that the addition of mannanase could hydrolyze the mannan adsorbed on cellulose and potentially improved hydrolysis efficiency of cellulose in lignocelluloses. Additionally, the mannanase supplementation could be extended to the removal of mannan on pulp by mannanase and finally affecting the dissolving pulps and paper quality. 相似文献
19.
Wei Liao Zhiyou Wen Sharon Hurley Yan Liu Chuanbin Liu Shulin Chen 《Applied biochemistry and biotechnology》2005,124(1-3):1017-1030
This study focused on the effect of hemicellulose and lignin on enzymatic hydrolysis of dairy manure and hydrolysis process
optimization to improve sugar yield. It was found that hemicellulose and lignin in dairy manure, similar to their role in
other lignocellulosic material, were major resistive factors to enzymatic hydrolysis and that the removal of either of them,
or for best performance, both of them, improved the enzymatic hydrolysis of manure cellulose. This result combined with scanning
electron microscope (SEM) pictures further proved that the accessibility of cellulose to cellulase was the most important
feature to the hydrolysis. Quantitatively, fed-batch enzymatic hydrolysis of fiber without lignin and hemicellulose had a
high glucose yield of 52% with respect to the glucose concentration of 17 g/L at a total enzyme loading of 1300 FPU/L and
reaction time of 160 h, which was better than corresponding batch enzymatic hydrolysis. 相似文献
20.
Yan Li Guozhu Li Yunling Zou Qingjun Zhou Xiaoxue Lian 《Cellulose (London, England)》2014,21(1):301-309
Cellulose nanofibers with a diameter of 70 nm and lengths of approximately 400 nm were fabricated from partly mercerized cotton fibers by acid hydrolysis. Morphological evolution of the hydrolyzed cotton fibers was investigated by powder X-ray diffraction, Fourier transform infrared analysis and field emission scanning electron microscopy. The XRD results show that the cellulose I was partially transformed into cellulose II by treatment with 15 % NaOH at 150° for 3 h. The crystallinity of this partially mercerized sample was lower than the samples that were converted completely to cellulose II by higher concentrations of NaOH. The intensities of all of the diffraction peaks were noticeably increased with increased hydrolysis time. Fourier transform infrared results revealed that the chemical composition of the remaining nanofibers of cellulose I and II had no observable change after acidic hydrolysis, and there was no difference between the hydrolysis rates for cellulose I or II. The formation of cellulose nanofibers involves three stages: net-like microfibril formation, then short microfibrils and finally nanofibers. 相似文献