Co-reporter:Ruizhen Wang, Tingting You, Guihua Yang, and Feng Xu
ACS Sustainable Chemistry & Engineering November 6, 2017 Volume 5(Issue 11) pp:10849-10849
Publication Date(Web):September 29, 2017
DOI:10.1021/acssuschemeng.7b02786
A two-step white rot–brown rot fungal pretreatment of corn cobs was proposed to enhance enzymatic hydrolysis efficiency while reducing the lengthy time requirement for the conventional fungal treatment process. Corn cobs were first pretreated by white rot fungi for 25 days, followed by short time brown rot fungi treated for 7 days. The results indicated that the enzymatic hydrolysis efficiency was dramatically improved as a result of the synergistic effects of combined pretreatments. The highest glucose yield of 83.0% was obtained by Trametes orientalis (Cui6300)–Fomitopsis pinicola (Cui12330) pretreatment. Chemical composition and FT-IR observations demonstrated that hemicelluloses were selectively degraded. Additionally, SEM analysis illustrated that the structural disruption of pretreated corn cobs occurred and might account for the enhancement of the hydrolysis efficiency. In this processing, 7 days of brown rot fungal treatment played a significant role in enzymatic hydrolysis enhancement. Cellulose content only decreased slightly in such a short time, which was in favor of hydrolysis. Overall, the two-step fungal pretreatment was competitive by using less processing time for high sugar yield.Keywords: Corn cobs; Enzymatic hydrolysis; FT-IR; SEM; Two-step fungal pretreatment;
Co-reporter:Meng Wang;Changyou Shao;Sukun Zhou;Jun Yang
RSC Advances (2011-Present) 2017 vol. 7(Issue 61) pp:38220-38230
Publication Date(Web):2017/08/02
DOI:10.1039/C7RA05506D
In this study, ultralight and hydrophobic carbon aerogels were prepared from 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO)-oxidized cellulose nanofibers (TOCN) for the removal of organic solvents. The morphological structure, density and chemical composition of TOCN aerogels frozen at −56 °C and −196 °C, followed by pyrolysis, were examined. The obtained carbon-based aerogels possessed an ultralight density of 8.8 mg cm−3 and excellent fire-resistance. The high porosity (up to 99.5%) and hydrophobicity (contact angle of 139.6°) of the obtained carbon aerogels allowed them to adsorb various organic solvents with a high absorption capacity (up to 110–260 g g−1). After five absorption–combustion and absorption–distillation cycles, the absorption capacity of the TOCN carbon aerogels exhibited excellent recyclability with up to 64–99% of the initial absorption capability, demonstrating potential applications in the oil-spill-cleanup field.
Co-reporter:Lupeng Shao, Xueming Zhang, Fushan Chen, Feng Xu
Journal of Analytical and Applied Pyrolysis 2017 Volume 128(Volume 128) pp:
Publication Date(Web):1 November 2017
DOI:10.1016/j.jaap.2017.11.003
•Pyrolysis of fractionated lignins by ultrafiltration were carried out by Py-GC/MS.•Molecular weight of lignin affected the relative content of pyrolytic products.•High molecular weight lignin favored the generation of G-type compounds at 500 °C.The pyrolysis behavior of different lignin samples fractionated by ultrafiltration membrane technology was investigated by pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS). Results indicated that the predominant products derived from pyrolysis of lignin fractions with different molecular weights changed in the relative content, but not in the compound species. At 500 °C, high molecular weight lignin favored the generation of guaiacol-type compounds (57.33%), and low molecular weight lignin produced more syringol-type compounds (34.33%). As temperature increased to 650 °C, methoxy groups in S and G units were easier to cleave from the benzene ring of the high molecular weight lignin leading to an increase in the relative content of phenol-type compounds. High molecular weight lignin was found to produce the highest amounts of phenol-type compounds (46.22%) and aromatic hydrocarbons (17.25%) at 800 °C, while low molecular weight lignin favored the generation of guaiacol-type and syingol-type compounds. The reveal of relevance between specific lignin fractions and pyrolysis behaviour is meaningful for the efficient transformation of lignin to specific aromatic compounds.
Co-reporter:Liming Zhang, Tingting You, Tian Zhou, Xia Zhou, and Feng Xu
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 22) pp:13918-13925
Publication Date(Web):May 16, 2016
DOI:10.1021/acsami.6b02774
The advent of bioethanol production has generated abundant lignin-derived byproducts which contain proteins and polysaccharides. These byproducts are inapplicable for direct material applications. In this study, lignin-derived byproducts were used for the first time as carbon precursors to construct an interconnected hierarchical porous nitrogen-doped carbon (HPNC) via hydrothermal treatment and activation. The obtained HPNC exhibited favorable features for supercapacitor applications, such as hierarchical bowl-like pore structures, a large specific surface area of 2218 m2 g–1, a high electronic conductivity of 4.8 S cm–1, and a nitrogen doping content of 3.4%. HPNC-based supercapacitors in a 6 M KOH aqueous electrolyte exhibited high-rate performance with a high specific capacitance of 312 F g–1 at 1 A g–1 and 81% retention at 80 A g–1 as well as an excellent cyclic life of 98% initial capacitance after 20 000 cycles at 10 A g–1. Moreover, HPNC-based supercapacitors in the ionic liquid electrolyte of EMI-BF4 displayed an enhanced energy density of 44.7 Wh kg–1 (remaining 74% of max value) at an ultrahigh power density of 73.1 kW kg–1. The proposed strategy may facilitate lignin utilization and lead to a green bioethanol production process.
Co-reporter:Zhe Ji, Xun Zhang, Zhe Ling, Run-Cang Sun, Feng Xu
Carbohydrate Polymers 2016 Volume 154() pp:247-256
Publication Date(Web):10 December 2016
DOI:10.1016/j.carbpol.2016.06.086
•DAP induced separation of cell walls in pith but not in rind.•The distribution of lignin droplets size differed from treated rind and pith.•Cellulose crystallinity was not a major factor affecting cellulose digestibility.•The changes of components distribution in rind and pith is cell type-dependent.The recalcitrance in grasses varies according to cell type and tissue. In this study, dilute acid pretreatment was performed on Miscanthus × giganteus internodes that include rind and pith regions which showing heterogeneous structural and chemical changes. Pretreatment on pith effectively hydrolyzed 73.33% hemicelluloses and separated cohesive cell walls from the compound middle lamella due to lignin migration. Lignin droplets with an average diameter of 49.5 ± 29.3 nm were concurrently coalesced on wall surface, that in turn exposed more microfibrils deep in walls to be enzymatically hydrolyzed reaching 82.55%. By contrast, the rind with a relatively intergrated cell structure was covered by larger lignin droplets (101.2 ± 44.1 nm) and filled with inaccessible microfibrils limiting enzymatic sacchrification (31.50%). Taken together, the cellulose digestibility of biomass was not majorly influenced by cellulose crystallinity, while it was strongly correlated with the positive effects of hemicelluloses degradation, lignin redistribution, cellulose exposure and loosening cell wall structure.
Co-reporter:Sheng Chen, Xun Zhang, Zhe Ling, Zhe Ji, Bandaru V. Ramarao, Shri Ramaswamy and Feng Xu
RSC Advances 2016 vol. 6(Issue 83) pp:79297-79306
Publication Date(Web):15 Aug 2016
DOI:10.1039/C6RA18333F
Liquid hot water (LHW) pretreatment is an effective method to improve enzymatic digestibility of lignocellulosic feedstock by removing hemicellulose/lignin. To better understand how LHW pretreatment reduces plant cell wall recalcitrance, we applied a combined approach using multiple microscopic techniques and chemometric methods to monitor microstructural and topochemical changes in the fiber cell wall of sugar maple (Acer saccharum). The heterogeneity of deconstruction in various cell wall layers was easily visualized based on chemical characterizations through confocal Raman microscopy, combining with principal component analysis and cluster analysis. Interestingly, after LHW pretreatment, the S2 layer was differentiated into two regions, namely a heavy-damaged region (outer and thin inner S2) with more polysaccharides removed, and a light-damaged region (middle S2) which still remained relatively intact. Our results have established a direct correlation between microstructural and topochemical changes of a cell wall following LHW pretreatment. The removal of polysaccharides (mainly hemicelluloses) rather than lignin played a critical role in the visible damage of the cell wall, like cavities, gaps and collapses.
Co-reporter:Dayong Ding;Xia Zhou;Zhe Ji;Tingting You
BioEnergy Research 2016 Volume 9( Issue 2) pp:601-609
Publication Date(Web):2016 June
DOI:10.1007/s12155-015-9703-1
Thorough understanding of how hemicelluloses removal influences cell wall nanoscale architecture and cellulose digestion is of crucial importance for enabling low-cost industrial conversion of lignocellulosic biomass to renewable biofuels. In this work, delignified poplar cell walls, after various degrees of hemicelluloses removal, were characterized by Fourier transform infrared imaging spectroscopy and atomic force microscopy to evaluate enhancement in cell wall digestibility. There was a gradual decrease in hemicelluloses content with dilute alkali treatment, which resulted in alterations in the nanoscale architecture and crystallinity of cell walls. Removal of hemicelluloses did not disrupt the integrity of microfibrils but resulted in exposure of microfibrils and a decrease in the diameter of microfibrils. X-ray analysis indicated that the increase in crystallinity beyond natural variations in the crystallinity of cellulose was mainly attributable to removal of hemicelluloses. In conclusion, alterations in the architecture and crystallinity of cell walls facilitated enzymatic digestion of delignified poplar, enhancing cellulose conversion from 68.24 to 75.16 %.
Co-reporter:Xun Zhang, Zhe Ji, Xia Zhou, Jian-Feng Ma, Ya-Hong Hu, and Feng Xu
Analytical Chemistry 2015 Volume 87(Issue 2) pp:1344
Publication Date(Web):December 22, 2014
DOI:10.1021/ac504144s
The technique of Raman spectroscopic imaging is finding ever-increasing applications in the field of wood science for its ability to provide spatial and spectral information about the sample. On the basis of the acquired Raman imaging data set, it is possible to determine the distribution of chemical components in various wood cell wall layers. However, the Raman imaging data set often contains thousands of spectra measured at hundreds or even thousands of individual frequencies, which results in difficulties accurately and quickly extracting all of the spectra within a specific morphological region of wood cell walls. To address this issue, the authors propose a new method to automatically identify Raman spectra of different cell wall layers on the basis of principal component analysis (PCA) and cluster analysis. A Raman imaging data set collected from a 55.5 μm × 47.5 μm cross-section of poplar tension wood was analyzed. Several thousand spectra were successfully classified into five groups in accordance with different morphological regions, namely, cell corner (CC), compound middle lamella (CML), secondary wall (SW), gelatinous layer (G-layer), and cell lumen. Their corresponding average spectra were also calculated. In addition, the relationship between different characteristic peaks in the obtained Raman spectra was estimated and it was found that the peak at 1331 cm–1 is more related to lignin rather than cellulose. Not only can this novel method provide a convenient and accurate procedure for identifying the spectra of different cell wall layers in a Raman imaging data set, but it also can bring new insights into studying the morphology and topochemistry in wood cell walls.
Co-reporter:Sukun Zhou, Meng Wang, Xiong Chen, and Feng Xu
ACS Sustainable Chemistry & Engineering 2015 Volume 3(Issue 12) pp:3346
Publication Date(Web):November 8, 2015
DOI:10.1021/acssuschemeng.5b01020
Sustainable microfibrillated cellulose (MFC) aerogels are considered to be good templates for the growth of functional organic or inorganic nanoparticles. In this work, MFC aerogels with high porosity (99.9%) and low density (2.91 mg/cm3) were produced by freeze-drying. Then the obtained MFC aerogels were used as templates for the synthesis of MFC/polypyrrole (PPy)/silver nanoparticles (Ag) hybrid aerogels by a simple dip-coating method. Our results demonstrated that the obtained hybrid aerogels maintained the attractive features of the pristine MFC aerogels, such as high porosity, low density, and high compressive stress, during the preparation process. Compared with MFC aerogels and MFC/PPy hybrid aerogels, the MFC/PPy/Ag hybrid aerogels exhibited enhanced antimicrobial and electrical conductive properties due to the combination of PPy and Ag. Moreover, the electrical conductivity and compressible properties of the MFC/PPy/Ag hybrid aerogels led to their pressure responsive property. These features make the hybrid aerogels promising candidates for wound healing, energy storage, and pressure sensing applications.Keywords: Antimicrobial; Dip-coating; Electrical conductive; Microfibrillated cellulose; Polypyrrole; Pressure responsive; Silver nanoparticles
Co-reporter:Xiong Chen, Jinghuan Chen, Tingting You, Kun Wang, Feng Xu
Carbohydrate Polymers 2015 Volume 125() pp:85-91
Publication Date(Web):10 July 2015
DOI:10.1016/j.carbpol.2015.02.054
•The crystal type of cellulose had great impact on cellulose dissolution.•The solubility of the cellulose I, II, and III was progressively decreased.•All the cellulose solutions showed good thermal stability.•The ability of celluloses to form hydrogen bonds with sodium hydroxides was similar.•The ability of cellulose I, II, III, and IV associated with urea was gradually increased in cellulose solution.This study focused on the effect of cellulose crystal type on the dissolution of cellulose in aqueous NaOH/urea. Cellulose I, II, IIII, and IVI were prepared and characterized. Subsequently, the solubility of these cellulose samples in aqueous NaOH/urea was tested and the mechanism was determined by a combination of 1H NMR spectroscopy and differential scanning calorimetry (DSC). The results indicated that, compared with the degree of polymerization (DP) and crystallinity index of cellulose, the cellulose crystal type had greater impact on cellulose dissolution. Specially, the solubility of the cellulose I, II, and III was progressively decreased, probably due to different hydrogen bond network and packing energy in it. The ability of cellulose I, II, III, and IV to form hydrogen bonds with sodium hydroxides was nearly the same, while gradually increased when cellulose preparations were associated with urea. Moreover, all the cellulose solutions showed good thermal stability.
Co-reporter:Sukun Zhou, Meng Wang, Jun Yang and Feng Xu
RSC Advances 2015 vol. 5(Issue 45) pp:35976-35984
Publication Date(Web):27 Mar 2015
DOI:10.1039/C5RA00475F
Transparent LAPONITE® RD/hydroxyethyl cellulose (LRD/HEC) nanocomposite films, with a full composition range of LRD (0–100 wt%), were fabricated via a facile vacuum filtration process. The influence of the LRD content on the nanostructure and mechanical properties of the nanocomposites was systematically investigated, and there exists two critical points at a LRD content of 40 wt% and 70 wt%. In the range of 0–40 wt%, the nanocomposites showed a blurry oriented structure and the mechanical performance of the nanocomposite was improved dramatically with the increase of LRD content. In the range of 40–70 wt%, the nanocomposites showed a clearly oriented lamellar nanostructure with alternating LRD nanoplatelets and HEC layers. The mechanical properties of the nanocomposite were further enhanced at a relatively low rate with the increase of the LRD content, and reached a maximum value at a LRD content of 70 wt%. At this optimum LRD content, the nanocomposite possessed a Young’s modulus of 7.09 GPa and a tensile strength of 126.66 MPa, which are 43 times and 5.5 times higher than those of pure HEC films, respectively. Whereas when the LRD content was higher than 70%, the lamellar nanostructure was converted to tactoids with deteriorated mechanical properties. It is expected that the results herein will offer deepened understanding for the fabrication of bioinspired multilayered nanocomposites.
Co-reporter:Tingting You, Liming Zhang, Siqin Guo, Lupeng Shao, and Feng Xu
Journal of Agricultural and Food Chemistry 2015 Volume 63(Issue 50) pp:10747-10756
Publication Date(Web):December 1, 2015
DOI:10.1021/acs.jafc.5b04831
Solid acid-enhanced ionic liquid (IL) pretreatment is of paramount importance for boosting the yield of sugars from biomass cost-effectively and environmentally friendly. To unravel the chemical and supramolecular structural changes of lignin after pretreatment, IL–acid lignin (ILAL) and subsequent residual cellulolytic enzyme lignin (RCEL) were isolated from Arundo donax Linn. The structural features were compared with those of the corresponding milled wood lignin (MWL). Results indicated that the pretreatment caused loss of β-O-4′, β-β′, β-1′ linkages and formation of condensed structures in lignin. A preferential breakdown of G-type lignin may have occurred, evidenced by an increased S/G ratio revealed by 2D HSQC NMR analysis. It was determined that the depolymerization of β-O-4′ linkage, lignin recondensation, and cleavage of ferulate–lignin ether linkages took place. Moreover, a simulation module was first developed to define morphological changes in lignin based on AFM and TEM analyses. Briefly, tree branch like aggregates was destroyed to monodisperse particles.
Co-reporter:Jun Yang, Chun-rui Han, Feng Xu and Run-cang Sun
Nanoscale 2014 vol. 6(Issue 11) pp:5934-5943
Publication Date(Web):01 Apr 2014
DOI:10.1039/C4NR01214C
The physical crosslinking of colloidal nanoparticles via dynamic and directional non-covalent interactions has led to significant advances in composite hydrogels. In this paper, we report a simple approach to fabricate tough, stretchable and hysteretic isotropic nanocomposite hydrogels, where rod-like cellulose nanocrystals (CNCs) are encapsulated by flexible polymer chains of poly(N,N-dimethylacrylamide) (PDMA). The CNC–PDMA colloidal clusters build a homogeneously cross-linked network and lead to significant reinforcing effect of the composites. Hierarchically structured CNC–PDMA clusters, from isolated particles to an interpenetrated network, are observed by transmission electron microscopy measurements. Dynamic shear oscillation measurements are applied to demystify the differences in network rheological behaviors, which were compared with network behaviors of chemically cross-linked PDMA counterparts. Tensile tests indicate that the hybrid hydrogels possess higher mechanical properties and a more efficient energy dissipation mechanism. In particular, with only 0.8 wt% of CNC loading, a 4.8-fold increase in Young's modulus, 9.2-fold increase in tensile strength, and 5.8-fold increase in fracture strain are achieved, which is ascribed to a combination of CNC reinforcement in the soft matrix and CNC–PDMA colloidal cluster conformational rearrangement under stretching. Physical interactions within networks serve as reversible sacrificial bonds that dissociate upon deformation, exhibiting large hysteresis as an energy dissipation mechanism via cluster mobility. This result contrasts with the case of chemically cross-linked PDMA counterparts where the stress relaxation is slow due to the permanent cross-links and low resistance against crack propagation within the covalent network.
Co-reporter:Ting-Ting You, Su-Kun Zhou, Jia-Long Wen, Chao Ma, and Feng Xu
Journal of Agricultural and Food Chemistry 2014 Volume 62(Issue 8) pp:1936-1944
Publication Date(Web):January 22, 2014
DOI:10.1021/jf4045414
Agricultural residues Castanea mollissima shells represent a promising resource for natural pigments for the food industry. This study provides a comprehensive and systematic evaluation of water-soluble pigments (CSP) from C. mollissima shells, which were obtained by 50% ethanol with microwave-assisted extraction. Spectroscopic techniques (UV, FT-IR, 13C NMR), elemental analysis, and chromatographic techniques (HPAEC, GPC) revealed that the main components in the CSP were flavonoids procyanidin B3 (condensed tannin), quercetin-3-O-glycoside, and steroidal sapogenins. As a consequence, CSP was water-soluble and presented significant DPPH scavenge capacity (EC50 value was 0.057 mg/mL). Specially, CSP gave excellent antibacterial activity, and even better than 5% aqueous phenol in some case. Moreover, CSP was practically nontoxic and exhibited good stability with temperature, natural light, and metal ions. These outstanding properties will enlarge the application of CSP for natural food additives production.
Co-reporter:Liming Zhang;Tingting You;Lu Zhang;Mingfei Li
Biotechnology for Biofuels 2014 Volume 7( Issue 1) pp:
Publication Date(Web):2014 December
DOI:10.1186/s13068-014-0189-4
Reducing the cost of producing cellulosic ethanol is essential for the industrialization of biorefinery. Several processes are currently under investigation, but few of these techniques are entirely satisfactory in terms of competitive cost or environmental impact. In this study, a new ethanol and lactic acid (LA) coproduction is proposed. The technique involved addition of waste alkaline peroxide pretreated hydrolysate (mainly LA and hemicelluloses) to the reaction mixture after ethanol fermentation (mainly LA and xylose) to reduce the ethanol production cost.The following processes were investigated to optimize LA production: no addition of hemicelluloses or hydrolysate, addition of recycled hemicelluloses, and addition of concentrated hydrolysate. The addition of concentrated hydrolysate at 48 hours, which resulted in a maximum LA concentration of 22.3 g/L, was the most environment-friendly and cost-effective process. After the improved fermentation, 361 mg LA and 132 mg ethanol were produced from 1 g of raw poplar wood. That is, the production of one gallon of ethanol produced $9 worth of LA.The amount of LA produced from the pretreated hydrolysate and reaction mixture after ethanol fermentation cannot be underestimated. The recovery of hydrolysate rich in LA and hemicelluloses (or xylose) significantly improved LA yield and further reduced the ethanol production cost.
Co-reporter:Ting-Ting You, Jian-Zhen Mao, Tong-Qi Yuan, Jia-Long Wen, and Feng Xu
Journal of Agricultural and Food Chemistry 2013 Volume 61(Issue 22) pp:5361-5370
Publication Date(Web):May 6, 2013
DOI:10.1021/jf401277v
As one of the potential energy crops, Arundo donax Linn. is a renewable source for the production of biofuels and bioproducts. In the present study, milled wood lignin (MWL) and alkaline lignin (AL) from stems and foliage of A. donax were isolated and characterized by FT-IR spectroscopy, UV spectroscopy, GPC, 31P NMR, 2D HSQC NMR, and DFRC. The results indicated that both stem and foliage lignins were HGS type lignins. The semiquantitative HSQC spectra analysis demonstrated a predominance of β-O-4′ aryl ether linkages (71–82%), followed by β-β′, β-5′, β-1′, and α,β-diaryl ethers linkages in the lignins. Compared to stem lignins, foliage lignins had less β-O-4′ alkyl-aryl ethers, lower weight-average molecular weight, less phenolic OH, more H units, and lower S/G ratio. Moreover, tricin was found to incorporate into the foliage lignins (higher content of condensed G units) in significant amounts and might be alkaline-stable.
Co-reporter:Ming-Fei Li, Shao-Ni Sun, Feng Xu, Run-Cang Sun
Ultrasonics Sonochemistry 2012 Volume 19(Issue 2) pp:243-249
Publication Date(Web):March 2012
DOI:10.1016/j.ultsonch.2011.06.018
Bamboo was submitted to ultrasound-assisted extraction in aqueous ethanol to evaluate the effect of ultrasonic irradiation on the dissolution of lignin. In this case, the dewaxed bamboo culms were subjected to ball milling for 48 h, and then were suspended in 95% ethanol followed by ultrasonic irradiations for varied times at 20 °C to obtain ethanol-soluble fractions. The structural and thermal properties of the ethanol-soluble fractions were comparatively investigated by chemical analysis including alkaline nitrobenzene oxidation, bound carbohydrate determination, FT-IR spectra, HSQC spectra, TG, and DTA. The results showed that the yields of the ethanol-soluble fractions were between 4.29% and 4.76% for the fractions prepared with ultrasonic irradiation time ranging from 5 to 55 min, as compared to 4.02% for the fraction prepared without ultrasonic irradiation. It was found that the lignin content of the fraction increased with the increase of the ultrasonic irradiation time. There was a slight increase of the molecular weight of the lignin with the increase of the ultrasonic irradiation time. Alkaline nitrobenzene oxidation coupled with HSQC analysis indicated that the lignin in the fractions was mainly composed of G S H type units as well as minor amounts of ferulic acids. In addition, the fraction prepared with ultrasonic irradiation exhibited a slightly higher thermal stability as compared to the fraction prepared without ultrasonic irradiation.Highlights► Dewaxed bamboo culms were extracted under ultrasonic irradiation. ► Ultrasonic irradiation enhanced the lignin content of the dissolved fraction. ► Ethanol-soluble bamboo lignins were composed of G S H units and ferulic acids. ► Ultrasonic irradiation increased the thermal stability of the dissolved fraction.
Co-reporter:Jing Bian, Feng Peng, Xiao-Peng Peng, Feng Xu, Run-Cang Sun, John F. Kennedy
Carbohydrate Polymers 2012 Volume 88(Issue 2) pp:638-645
Publication Date(Web):2 April 2012
DOI:10.1016/j.carbpol.2012.01.010
Seven hemicellulosic fractions were extracted with 10% KOH from delignified sugarcane bagasse for 10 h at 20, 25, 30, 35, 40, 45, and 50 °C, respectively. Chemical composition and structural features of all the fractions were investigated by a combination of HPAEC, GPC, FT-IR, 1D (1H, 13C) and 2D (HSQC) NMR spectra, and TGA-DTA. Notable differences in the molecular weights were observed that the fractions extracted at 20 °C, 25 °C, and 30 °C showed relatively lower molecular weights (68, 400–76, 900 g mol−1) and the extraction at elevated temperatures from 35 to 50 °C yielded the hemicellulosic populations of somewhat higher Mw (80, 400–93, 300 g mol−1). However, the differences in the yield, chemical composition, structural features and thermal stability were much less pronounced in this study. The results also suggested that all the hemicellulosic polymers had a backbone of (1 → 4)-β-d-xylan and mainly substituted with (1 → 2) and (1 → 3)-linked arabinofuranosyl residues, and also with 4-O-methyl-d-glucuronic acid linked to O-2 of the backbone.Highlights► Seven alkali-soluble hemicelluloses were obtained with KOH from 20 to 50 °C. ► Samples were mainly composed of xylose and small amounts of other sugar components. ► Higher temperatures (30–50 °C) yielded hemicelluloses with higher molecular weights. ► Structure of hemicelluloses was proposed via multiple spectroscopy.
Co-reporter:Ming-Fei Li, Shao-Ni Sun, Feng Xu, Run-Cang Sun
Food Chemistry 2012 Volume 134(Issue 3) pp:1392-1398
Publication Date(Web):1 October 2012
DOI:10.1016/j.foodchem.2012.03.037
Microwave-assisted extraction in organic acid aqueous solution (formic acid/acetic acid/water, 3/5/2, v/v/v) was applied to isolate lignin from bamboo. Additionally, the structural features of the extracted lignins were thoroughly investigated in terms of C9 formula, molecular weight distribution, FT-IR, 1H NMR and HSQC spectroscopy. It was found that with an increase in the severity of microwave-assisted extraction, there was an increase of phenolic hydroxyl content in the lignin. In addition, an increase of the severity resulted in a decrease of the bound carbohydrate content as well as molecular weight of the lignin. Antioxidant activity investigation indicated that the radical scavenging index of the extracted lignins (0.35–1.15) was higher than that of BHT (0.29) but lower than that of BHA (3.85). The results suggested that microwave-assisted organic acid extraction provides a promising way to prepare lignin from bamboo with good antioxidant activity for potential application in the food industry.Highlights► Bamboo lignin was extracted by microwave heating assisted by organic acids. ► Increasing extraction severity resulted in increased phenolic hydroxyl content. ► The extracted lignin had antioxidant activity higher than BHT. ► Extraction at 109 °C for 60 min resulted in a lignin yield of 17.98%.
Co-reporter:Ming-Fei Li, Shao-Ni Sun, Feng Xu, and Run-Cang Sun
Journal of Agricultural and Food Chemistry 2012 Volume 60(Issue 7) pp:1703-1712
Publication Date(Web):January 29, 2012
DOI:10.1021/jf2050608
Fractionation of lignocellulosic material into its constitutive components is of vital importance for the production of biofuels as well as other value-added chemicals. The conventional acetosolv processes are mainly focused on the production of pulp from woody lignocelluloses. In this study, a mild acetosolv process was developed to fractionate bamboo under atmospheric pressure to obtain cellulosic pulp, water-soluble fraction, and acetic acid lignin. The structural features of the lignins obtained under various conditions were characterized with elemental analysis, sugar analysis, alkaline nitrobenzene oxidation, gel permeation chromatography (GPC), 1H nuclear magnetic resonance (1H NMR), and heteronuclear single-quantum coherence (HSQC) spectroscopy. As compared to milled wood lignin (MWL) of bamboo, acetic acid lignins had low impurities (carbohydrates 2.48–4.56%) mainly due to the cleavage of linkages between lignin and carbohydrates. In addition, acetic acid lignins showed a low proportion of syringyl (S) units. Due to the cleavage of linkages between lignin units, acetic acid lignins had weight-average molecular weights ranging from 4870 to 5210 g/mol, less than half that of MWL (13000 g/mol). In addition, acetic acid lignins showed stronger antioxidant activity mainly due to the significant increase of free phenolic hydroxyls. The lignins obtained with such low impurities, high free phenolic hydroxyls, and medium molecular weights are promising feedstocks to replace petroleum chemicals.
Co-reporter:Shao-Ni Sun, Ming-Fei Li, Tong-Qi Yuan, Feng Xu, and Run-Cang Sun
Journal of Agricultural and Food Chemistry 2012 Volume 60(Issue 44) pp:11120-11127
Publication Date(Web):October 12, 2012
DOI:10.1021/jf3021464
Pretreatment is the key to unlock the recalcitrance of lignocellulosic biomass for the productions of biofuels. Ionic liquid pretreatment has drawn increased attention because of its numerous advantages over conventional methods. In this study, corncob was submitted to pretreatments with 1-ethyl-3-methylimadazolium acetate (EMIMAc) and/or H2O/dimethyl sulfoxide (DMSO) followed by alkaline extraction to isolate hemicelluloses. The hemicellulosic fractions obtained were comprehensively characterized with a series of chemical and spectroscopic technologies, including gel permeation chromatography (GPC), thermogravimetric analysis (TGA), high-performance anion-exchange chromatography (HPAEC), Fourier transform infrared (FTIR) spectroscopy, and one- and two-dimensional nuclear magnetic resonance (NMR). The results showed that the fractions prepared with ionic liquid pretreatments exhibited relatively higher average molecular weights (196 230–349 480 g/mol) than the fraction prepared without pretreatment (Mw, 96 260 g/mol). Furthermore, the pretreated fractions demonstrated higher thermal stability compared to the fractions without pretreatment. Structural characterization indicated that all of the fractions had similar structures, which are composed of a (1 → 4)-linked β-d-xylopyranosyl backbone substituted with arabinofuranosyls attached to O-2 and O-3 and with 4-O-methyl-α-d-glucuronic acid also linked to O-2.
Co-reporter:Ming-Fei Li, Shao-Ni Sun, Feng Xu, Run-Cang Sun
Separation and Purification Technology 2012 Volume 101() pp:18-25
Publication Date(Web):13 November 2012
DOI:10.1016/j.seppur.2012.09.013
Value-added utilization of lignin is affected by its heterogeneous nature. In this case, bamboo organosolv lignin was successively fractionated with organic solvents of increasing dissolving capacity (i.e., ether, ethyl acetate, methanol, acetone, and dioxane/water) to obtain homogeneous preparations. The starting lignin and the fractions obtained were compared in terms of molecular weight distribution and functional groups by a set of chemistry and spectroscopy technologies. It was found that the yield of the five fractions obtained was 2.80%, 39.85%, 18.64%, 23.38%, and 13.30%, respectively. The lignin fraction extracted with ethyl acetate contained homogeneous materials of low molecular weight whereas the lignin fraction extracted with acetone was composed of a mixture of medium and high molecular weight materials. As evidenced by sugar analysis, there was strong association between hemicelluloses and lignin in the preparations with different molecular weights. Spectroscopy analysis indicates that with increasing the dissolving capacity of solvent, the contents of methoxyl, phenolic, and aliphatic hydroxyl groups in the extracted lignin fractions were decreased. The lignin fraction extracted with ethyl acetate, having a high radical scavenging index (RSI), will be a good feedstock as stabilizer. The results above suggest that the sequential solvent fractionation provides a promising way to prepare lignin with homogeneous structure and good functional properties for potential application.Graphical abstractHighlights► Heterogeneous organosolv lignin was sequentially extracted with organic solvents. ► Sequential solvent fractionation prepared homogeneous lignin fractions. ► Increasing dissolving capacity resulted in decreased phenolic hydroxyl content. ► Ethyl acetate-extracted fraction has a high antioxidant capacity.
Co-reporter:Jing Bian;Feng Peng;Pai Peng;Run-Cang Sun
Journal of Applied Polymer Science 2012 Volume 124( Issue 4) pp:3154-3164
Publication Date(Web):
DOI:10.1002/app.34835
Abstract
Hemicellulosic polymers A and B were isolated from Populus gansuensis by extracting the chlorite-delignified residue with 10% KOH. Fractional precipitation of hemicellulose B by graded ethanol resulted in six subfractions varying in yield, molecular size distribution, and sugar composition. Macromolecular and more linear hemicellulosic polymers with higher yields were preferentially precipitated in relatively lower ethanol concentrations, while more branched and complex hemicellulosic polymers with lower molecular weights were obtained in relatively higher ethanol concentrations. Chemical and spectral evidence suggested that H30 subfraction obtained by 30% ethanol precipitation was assumed to be 4-O-methyl-D-glucurono-D-xylans, with 4-O-methyl-D-glucuronic acid linked to C-2 of (14)-β-D-xylan. On average for every six D-xylopyranosyl residues, there is one 4-O-methyl-D-glucuronic acid group. Hemicellulosic subfraction H75 precipitated at the ethanol concentration of 75% was more branched, and presumed to be heterogeneous mixture of arabinoglucurnoxylan and galactoglucomannan. In addition, the thermal stability of the linear large molecular hemicellulosic subfraction H30 appeared higher than the branched subfraction H75. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Co-reporter:Ming-Fei Li;Shao-Ni Sun;Run-Cang Sun
Journal of Applied Polymer Science 2012 Volume 125( Issue 1) pp:274-282
Publication Date(Web):
DOI:10.1002/app.35551
Abstract
Benzylated bamboo was mildly synthesized in nonaqueous medium without mercerization pretreatment. The ball-milled bamboo was firstly preswelled in lithium chloride/dimethyl sulfoxide (LiCl/DMSO) solution and then reacted with benzyl chloride in the presence of solid NaOH with varying molar ratios of benzyl chloride to OH groups of bamboo (1–4), reaction times (1–8 h), and temperatures (60–90°C). Benzylated bamboo products with yields from 51.1 to 106.9% and with degrees of substitution [DS, apparent value evaluated by Fourier transform infrared (FTIR) spectra] between 0.2 and 1.2 were synthesized. FTIR and 13C cross polarization/magic angle spinning nuclear magnetic resonance (CP/MAS NMR) spectroscopy confirmed the incorporation of benzyl groups into bamboo; SEM observations of the highly benzylated bamboo showed porous surface with small irregular slices ascribed to the disruption of intermolecular and intramolecular hydrogen bonds between cellulose. Because of the degradation of amorphous components, the crystallinity decreased negligibly after modification and the thermal stability increased slightly but was lower than that of cellulose. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Co-reporter:Ming-Fei Li, Shao-Ni Sun, Feng Xu, Run-Cang Sun
European Polymer Journal 2011 Volume 47(Issue 9) pp:1817-1826
Publication Date(Web):September 2011
DOI:10.1016/j.eurpolymj.2011.06.013
Cold NaOH/urea aqueous dissolved cellulose was studied for the synthesis of benzyl cellulose by etherification with benzyl chloride. By varying the molar ratios of benzyl chloride to OH groups in cellulose (1.5–4.0) and reaction temperatures (65–70 °C), benzyl cellulose with a degree of substitutions (DS) in the range of 0.29–0.54 was successfully prepared under such mild conditions. The incorporation of benzyl groups into cellulose was evidenced by multiple spectroscopies, including FT IR, 1H NMR, 13C NMR, CP/MAS 13C NMR and XRD. In addition, the thermal stability and surface morphology of the benzyl cellulose was also investigated with regard to the degree of substitution. The results indicated that the benzyl cellulose product with a low DS (0.51) in the present study reached the same solubility in many organic solvents as compared to those prepared in heterogeneous media. After benzylation, the sample decomposed at a lower temperature with a wider temperature range, which indicated that the thermal stability of benzyl cellulose was lower than that of the native cellulose. In addition, benzylation resulted in a pronounced reduction in crystallinity as well as a fundamental alteration of morphology of the native cellulose.Graphical abstractHighlights► Cold NaOH/urea aqueous dissolved cellulose was etherified to produce benzyl cellulose. ► Benzyl cellulose with a low DS achieved good solubility in many organic solvents. ► Benzylation resulted in a pronounced reduction in crystallinity. ► Fundamental alteration of cellulose morphology occurred after benzylation.
Co-reporter:Tong-Qi Yuan, Shao-Ni Sun, Feng Xu, and Run-Cang Sun
Journal of Agricultural and Food Chemistry 2011 Volume 59(Issue 12) pp:6605-6615
Publication Date(Web):May 16, 2011
DOI:10.1021/jf2003865
To improve yields while minimizing the extent of mechanical action (just 2 h of planetary ball-milling), the residual wood meal obtained from extraction of milled wood lignin (MWL) was sequentially treated with cellulolytic enzyme and alkali, and the yields of MWL, cellulolytic enzyme lignin (CEL), and alkaline lignin (AL) were 5.4, 23.2, and 16.3%, respectively. The chemical structures of the lignin fractions obtained were characterized by carbohydrate analysis, gel permeation chromatography (GPC), Fourier transform infrared (FT-IR) spectroscopy, and various advanced NMR spectroscopic techniques. The results showed that the lignin isolated as MWL during the early part of ball milling may originate mainly from the middle lamella. This lignin fraction was less degradable and contained more linear hemicelluloses and more C═O in unconjugated groups as well as more phenolic OH groups. Both 1D and 2D NMR spectra analyses confirmed that the lignin in triploid of Populus tomentosa Carr. is GSH-type and partially acylated at the γ-carbon of the side chain. Two-dimensional heteronuclear single-quantum coherence (13C–1H) NMR of MWL, CEL, and AL showed a predominance of β-O-4′ aryl ether linkages (81.1–84.5% of total side chains), followed by β-β′ resinol-type linkages (12.2–16.4%), and lower amounts of β-5′ phenylcoumaran (2.1–2.6%) and β-1′ spirodienone-type (0.4–1.4%) linkages. The syringyl (S)/guaiacyl (G) ratios were estimated to be 1.43, 2.29, and 2.83 for MWL, CEL, and AL, respectively.
Co-reporter:Yong-Chang Sun, Jia-Long Wen, Feng Xu, Run-Cang Sun
Polymer Degradation and Stability 2011 Volume 96(Issue 8) pp:1478-1488
Publication Date(Web):August 2011
DOI:10.1016/j.polymdegradstab.2011.05.007
Three organosolv- and three alkali-soluble hemicellulosic polymers were degraded from dewaxed Tamarix austromongolica (TA) with DMSO, 70% ethanol containing 2% triethylamine (TEA), 70% ethanol containing 0.5% NaOH at 70 °C for 5 h, and 1 M KOH, 1 M NaOH and 1 M NH3·H2O at 50 °C for 5 h, respectively. Comparative studies showed that more linear hemicelluloses were easy to obtain in NaOH and KOH aqueous solution, which have larger molecular weights (M¯w, 24,100–28,500 g mol−1), and contained mainly xylose (72.5–73.6%) and uronic acids (11.1–11.4%). The thermal degradation behaviour showed that significant degradation in the range from 190 to 390 °C, and more branched polymer was more easily degraded at low temperatures. FT-IR and 2D HSQC spectra showed that the major chemical structure of the KOH-soluble hemicelluloses consists of a linear backbone of (1 → 4)-β-d-xylopyranosyl residues, and at least one of the xylose residue is monosubstituted at O-2 by a 4-O-methylglucuronic acid, and l-arabinose attached to O-3 of the xylose residues, giving a typical ratio of arabinose/4-O-methyl-α-d-GlcpA/xylose is estimated to be 1:4:23.
Co-reporter:Tong-Qi Yuan, Shao-Ni Sun, Feng Xu, and Run-Cang Sun
Journal of Agricultural and Food Chemistry 2011 Volume 59(Issue 19) pp:10604-10614
Publication Date(Web):September 1, 2011
DOI:10.1021/jf2031549
To characterize the lignin structures and lignin–carbohydrate complex (LCC) linkages, milled wood lignin (MWL) and mild acidolysis lignin (MAL) with a high content of associated carbohydrates were sequentially isolated from ball-milled poplar wood. Quantification of their structural features has been achieved by using a combination of quantitative 13C and 2D HSQC NMR techniques. The results showed that acetylated 4-O-methylgluconoxylan is the main carbohydrate associated with lignins, and acetyl groups frequently acylate the C2 and C3 positions. MWL and MAL exhibited similar structural features. The main substructures were β-O-4′ aryl ether, resinol, and phenylcoumaran, and their abundances per 100 Ar units changed from 41.5 to 43.3, from 14.6 to 12.7, and from 3.7 to 4.0, respectively. The S/G ratios were estimated to be 1.57 and 1.62 for MWL and MAL, respectively. Phenyl glycoside and benzyl ether LCC linkages were clearly quantified, whereas the amount of γ-ester LCC linkages was ambiguous for quantification.
Co-reporter:Jia-Long Wen, Ling-Ping Xiao, Yong-Chang Sun, Shao-Ni Sun, Fu Xu, Run-Cang Sun, Xun-Li Zhang
Carbohydrate Research 2011 Volume 346(Issue 1) pp:111-120
Publication Date(Web):3 January 2011
DOI:10.1016/j.carres.2010.10.006
The physicochemical properties and structural characteristics of seven alkali-soluble hemicellulosic preparations were determined. These were extracted from bamboo (Bambusa rigida) with 1 M NaOH, KOH, LiOH, NH3·H2O, (CH3CH2)3N, Ca(OH)2, Ba(OH)2, respectively, at 50 °C for 3 h, were comparatively studied. Sugar analysis showed that these hemicelluloses contained d-xylose as the major constituent, along with d-glucose and l-arabinose in noticeable amounts. Uronic acids, principally 4-O-methyl-d-glucuronic acid, occurred in a small amount. Furthermore, based on the sugar analysis and FTIR and NMR spectroscopy, it can be concluded that the hemicelluloses consist of a backbone of β-(1→4)-linked d-xylopyranosyl units having branches of arabinose and 4-O-methyl-d-glucuronic acid. Nitrobenzene oxidation revealed that the hemicelluloses obtained are mostly free of bound lignins. Moreover, it is noteworthy that hemicelluloses isolated with the different alkaline solutions presented different chemical compositions and slightly dissimilar structural features, indicating that alkalinity played an important role in cleaving the chemical linkages between the hemicelluloses and the lignins.
Co-reporter:Lingping Xiao;Run-Cang Sun
Fibers and Polymers 2011 Volume 12( Issue 3) pp:
Publication Date(Web):2011 June
DOI:10.1007/s12221-011-0316-9
Successive extractions of the dewaxed Caragana sinica with 70 % ethanol, 70 % ethanol containing 1 % NaOH, 1 M KOH, 1 M NaOH, 3 M KOH, and 3 M NaOH at 75 °C for 3 h released 80.4 % of the original lignin. The physico-chemical properties and structural features of these lignin fractions were comprehensively characterized by alkaline nitrobenzene oxidation, GPC and two-dimensional NMR spectroscopy. The results showed that all the lignin fractions had relatively lower molecular average-weights ranging between 910 and 1630 g/mol. Moreover, 2D-NMR showed that the lignin fraction L2 isolated with 70 % ethanol containing 1 % NaOH from C. sinica was similar to a hardwood lignin, with a high S/G ratio accounted for 1.2, a predominance of β-O-4′ aryl ether linkages (77 % of all side-chains), followed by β-β′ resinol-type linkages (8 %) and lower amounts of β-5′ phenylcoumaran substructures (7 %), β-1′ spirodienone-type linkages (3 %), and cinnamyl end groups (5 %). The high predominance of the S-lignin units, together with the high proportion of β-O-4′ aryl ether linkages could contribute to a relatively high reactivity of C. sinica lignin during alkaline pulping.
Co-reporter:Jing Bian, Feng Peng, Feng Xu, Run-Cang Sun, John F. Kennedy
Carbohydrate Polymers 2010 Volume 80(Issue 3) pp:753-760
Publication Date(Web):5 May 2010
DOI:10.1016/j.carbpol.2009.12.023
Sequential treatments of dewaxed Caragana korshinskii with dimethyl sulfoxide and dioxane-triethylamine (9:1, v/v) at 80 °C for 5 h, saturated barium hydroxide, 1 M potassium hydroxide and 1 M sodium hydroxide at 50 °C for 5 h, and 3 M potassium hydroxide at 50 °C for 4 h released 9.9%, 12.1%, 19.2%, 27.7%, 13.2% and 12.9% of the original hemicelluloses, respectively. The DMSO-soluble and four alkali-soluble hemicellulosic fractions contained higher amounts of xylose (73.6–91.5%), but were lower in rhamnose (0.5–2.3%) and arabinose (2.8–17.6%) than dioxane-triethylamine (9:1, v/v) soluble hemicellulosic fraction, in which xylose (37.9%), rhamnose (25.9%) and arabinose (25.0%) were the major sugar components. In comparison, the molecular-weight analysis showed that hemicelluloses were substantially degraded with a value of 13,930 g mol−1 under the organic alkaline extraction condition (dioxane-triethylamine, 9:1) used, whereas saturated Ba(OH)2 treatment favored the solubilization of macromolecular hemicelluloses (69,910 g mol−1). It is confirmed that the hemicelluloses from C. korshinskii are (1 → 4)-linked β-d-xylans with l-arabinofuranosyl group attached based on both 1H and 13C NMR spectra.
Co-reporter:Jing Bian, Feng Peng, Pai Peng, Feng Xu, Run-Cang Sun
Carbohydrate Research 2010 Volume 345(Issue 6) pp:802-809
Publication Date(Web):19 April 2010
DOI:10.1016/j.carres.2010.01.014
Caragana korshinskii hemicelluloses were isolated with 10% KOH at 25 °C for 10 h from the delignified materials. The alkali-extractable hemicelluloses were then successively sub-fractionated by graded precipitation at final ethanol concentrations of 10%, 20%, 30%, 45%, 60%, and 80%, respectively. Neutral sugars and molecular weight analyses of the six hemicellulosic subfractions revealed that the molecular weights and the distribution of branches along the xylan backbone are different among the hemicellulosic fractions obtained in various ethanol concentrations. The less branched hemicelluloses with large molecules were precipitated in lower ethanol percentages, while with the increasing ethanol concentrations, more branched hemicelluloses with low molecular weights were obtained. 1H and 13C NMR studies revealed that the hemicellulosic subfraction precipitated at an ethanol concentration of 45% had a backbone of d-xylose residues and were branched mainly through 4-O-methyl-α-d-glucopyranosyl units.
Co-reporter:Zhe Ling, Sheng Chen, Xun Zhang, Feng Xu
Bioresource Technology (January 2017) Volume 224() pp:
Publication Date(Web):1 January 2017
DOI:10.1016/j.biortech.2016.10.064
•Crystallinity and crystallite size reduced under high alkaline concentration.•Low yield for 8 wt% NaOH were induced by increased crystallinity and hemicelluloses.•Mercerization to cellulose II allomorph enhanced the enzymatic accessibility.•Crystallinity of cellulose II provided a positive effect on enzymatic hydrolysis.The study aimed to explore the crystallinity and crystalline structure of alkaline pretreated cellulose. The enzymatic hydrolysis followed by pretreatment was conducted for measuring the efficiency of sugar conversion. For cellulose Iβ dominated samples, alkaline pretreatment (<8 wt%) caused increased cellulose crystallinity and depolymerized hemicelluloses, that were superimposed to affect the enzymatic conversion to glucose. Varying crystallite sizes and lattice spacings indicated the separation of cellulose crystals during mercerization (8–12 wt% NaOH). Completion of mercerization was proved under higher alkaline concentration (14–18 wt% NaOH), leading to distortion of crystalline cellulose to some extent. Cellulose II crystallinity showed a stimulative impact on enzymatic hydrolysis due to the weakened hydrophobic interactions within cellulose chains. The current study may provide innovative explanations for enhanced enzymatic digestibility of alkaline pretreated lignocellulosic materials.
Co-reporter:Liming Zhang, Tingting You, Tian Zhou, Lu Zhang, Feng Xu
Industrial Crops and Products (August 2016) Volume 86() pp:155-162
Publication Date(Web):1 August 2016
DOI:10.1016/j.indcrop.2016.03.041
•Combined treatment was used to improve poplar enzymatic digestibility.•Alkaline treatment is the optimized combination with white-rot fungi treatment.•Alkaline treatment dissolved humin and partially degraded residual lignin.•Enzymatic digestibility was increased to 89.3%.White-rot fungi pretreatment is one of the most environment-friendly pretreatment methods because of low chemical and energy requirement. However, apart from time consuming, white-rot fungi treatment results in inefficient delignification and humin formation, both of which inhibit subsequent enzymatic hydrolysis. Combined alkaline treatment for partial depolymerization of residual lignin and dissolution of humin is an efficient option for the conversion of white-rot pretreated samples. In the work presented, combined treatments increased the enzymatic digestibility to 89.3%, compared with 10.6% for untreated sample and 12.9% for solely white-rot treated samples. Highest digestibility of cellulose was achieved after 8 weeks of white-rot treatment and alkaline treatment at 120 °C, whereas sugar yield was highest from sole alkaline treatment at 160 °C. The efficient conversion can be ascribed to synergistic interaction between white-rot and alkaline treatments, resulting in increased enzymatic accessibility of cellulose. Therefore, white-rot fungi treatment is a green process that can efficiently decrease energy consumption, and in combination with alkaline treatment is highly effective in promoting sugar conversion.
![(2R,2'R,3S,3'S,4S)-2,2'-Bis(3,4-dihydroxyphenyl)-[4,8'-bichroman]-3,3',5,5',7,7'-hexaol](http://img.cochemist.com/ccimg/23600/23567-23-9.png)
![(2R,2'R,3S,3'S,4S)-2,2'-Bis(3,4-dihydroxyphenyl)-[4,8'-bichroman]-3,3',5,5',7,7'-hexaol](http://img.cochemist.com/ccimg/23600/23567-23-9_b.png)
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![2-(3,4-dihydroxyphenyl)-5,7-dihydroxy-3-[(2R,3S,4R,5S,6S)-3,4,5-trihydroxy-6-(hydroxymethyl)tetrahydropyran-2-yl]oxy-chromen-4-one](http://img.cochemist.com/ccimg/500/482-35-9_b.png)
