Xylan Yield Research Articles

Novel approach on the evaluation of enzyme-aided alkaline extraction of polysaccharide from Hordeum vulgare husk and molecular insight on the multifunctional scaffold

Hordeum vulgare husk, a cereal grain, is rich in dietary fiber and prebiotics beneficial for the gut microbiota and host organism. This study investigates the effects of barley husk-derived water-soluble xylan (BH-WSX) on gut homeostasis and the microbiome. We enzymatically extracted BH-WSX and evaluated its prebiotic and antioxidant properties. A 40.0 % (w/v) xylan yield was achieved, with the extracted xylan having a molecular mass of 212.0885 and a xylose to glucuronic acid molar ratio of 6:1. Specialized optical rotation research indicated that the isolated xylan is composed of monomeric sugars such as D-xylose, glucose, and arabinose. Fourier Transform Infrared (FTIR) spectroscopy revealed that the xylan comprises β (1 → 4) linked xylose units, randomly substituted with glucose residues, α-arabinofuranose, and acetyl groups. Nuclear Magnetic Resonance (NMR) analysis showed that the barley husk extract's backbone is substituted with 4-O-methyl glucuronic acid at the O2 position. Thermogravimetric analysis indicated that WSX exhibits a single sharp peak at 266 °C on the Differential Thermal Gravimetry (DTG) curve. Furthermore, a combination of in vitro, in vivo models, and molecular docking analysis elaborated on the anti-adhesion properties of BH-WSX. This study presents a novel approach to utilizing barley husk as an efficient source of functional polysaccharides for food-related industrial applications.

Xylooligosaccharides produced from sugarcane leaf arabinoxylan using xylanase from Aureobasidium pullulans NRRL 58523 and its prebiotic activity toward Lactobacillus spp.

In an attempt to enhance the value of sugarcane leaf, xylan was extracted and used for xylooligosaccharide (XO) production via enzymatic hydrolysis using xylanase from the black yeast Aureobasidium pullulans. The xylan was extracted from sugarcane leaf using alkali extraction according to the response surface methodology. The highest xylan yield (99.42 ± 4.05 % recovery) was obtained using 14.32 % (w/v) NaOH, 13.25:1 liquid: solid ratio, at 121 °C and 15 lb.in2 for 32 min. Sugar composition and FTIR spectrum analyses confirmed its structure as arabinoxylan. The extracted arabinoxylan had a relatively high molecular weight compared to previous studies. Crude endoxylanase from A. pullulans NRRL 58523 was selected for enzymatic hydrolysis of the xylan. The enzyme hydrolyzed well at 50 °C, pH 4.0 and was relatively stable under this condition (87.38 ± 1.26 % of the activity remained after 60 h). XOs, especially xylobiose and xylotriose, were obtained at the maximum yield of 237.51 ± 17.69 mg/g xylan via endoxylanase hydrolysis under the optimum conditions (50 °C, pH 4.0, 65.31 U/g xylan, 53 h). XOs exhibited species-specific prebiotic activity toward three strains of Lactobacillus spp. but not toward Bifidobacterium spp.

The effects of holocellulose treatments on the yield and structure of dimethylsulfoxide-extracted birchwood xylans

Xylans with naturally occurring acetylation are vital to the plant cell wall functionalities and are also demonstrating excellent dispersing properties which can be applied in fine chemicals and advanced materials. The acetyl structure of xylan can be maintained by dimethyl sulfoxide (DMSO) extraction. A disadvantage of DMSO extraction is that its yield is much lower than that of alkali extraction, which is unfavorable to the research and application of xylans. In this study, sodium chlorite was used as the delignification method to produce holocellulose from birch wood. The effects of subsequent holocellulose solvent exchange, drying and ball-milling on xylan DMSO extraction were studied. The differences of three successive DMSO extractions from the same holocellulose sample and gradient xylan precipitation from DMSO were also evaluated. The majority of xylans are extracted in the first two extractions, while the xylans extracted in the third extraction usually had low yields and low molecular weights. Xylans extracted directly from aqueously wet holocellulose without drying had a very low yield of less than 1%, while xylans extracted from freeze or vacuum dried holocellulose have total yields of 4–9%. T-butanol or ether washed holocellulose shows slightly lower xylan yield than water washed holocellulose. Ball milled holocellulose has twice the xylan yield of holocellulose sample without ball milling. For gradient xylan precipitation, more than 95% of the xylans precipitate in 50% and 70% ethanol. Gradient ethanol precipitation fractionates xylans by molecular weight, but does not fractionate xylans by degree of acetylation. This study is significant for promoting the researches and applications of DMSO extraction of xylan.

Optimization of hydrothermal-assisted alkali process for enhanced xylan recovery from banana fiber biomass

Banana fiber is a rich lignocellulosic biomass source that has not been widely explored. The hemicellulose components (15 - 20 %) of banana fiber can be a feedstock for producing high-value commodity chemicals. Hemicellulose is extracted by physical, chemical, and biological methods, in which combining hydrothermal treatment with alkaline mode of extraction provides an enhanced recovery percentage. Thus, the present study aimed to optimize the hydrothermal-assisted alkaline method of xylan extraction from the banana fiber biomass. Initially, xylan was extracted with a conventional-based alkali method. A maximum of about 43 and 35 % was recovered from pretreated and raw banana fiber at 12% NaOH concentration when incubated at 55 °C for 24 h. To improve the xylan yield, the hydrothermal assisted alkali method experimented in which 67.1% and 58.3 % of xylan were recovered when treated at 121 °C for 1 h at 12% NaOH. To further enhance the xylan recovery, a two-step alkali process by combining conventional and hydrothermal-assisted alkali methods resulted in the highest xylan (81%) recovery from pretreated banana fiber when incubated with 12 % alkali for 8 h followed by steam treatment. On the other hand, a maximum of 73 % of xylan was recovered when steam treated after incubation for 24 h from raw banana fiber. Thus, the alkali incubation followed by steam treatment significantly showed the highest xylan recovery from the banana fiber biomass. The extracted xylan might be utilized as a source for various xylan-based products, including furfural, xylooligosaccharides, xylose, and xylitol, all of which have significant roles in the pharmaceutical and food industries.

Coupling Preparation of Reconstituted-Bamboo-Board and Xylooligosaccharide via Hydrothermal Desaccharification Catalyzed by Slight Solid Alkali

Low-temperature carbonization is usually used to decompose bamboo hemicellulose to improve anti-decay and anti-mildew properties of bamboo board. Since xylan extraction from bamboo can produce xylo-oligosaccharides, there is a good coupling point between bamboo desaccharification and xylo-oligosaccharide production. In this study, the solution of xylan in bamboo and the controllable degree of polymerization hydrolysis could be achieved by solid base catalytic hydrothermal desugar treatment as well as the mechanical properties of bamboo could be maintained. The yield of xylan was up to 16.8% by appropriate alkali-suppressed method. In addition, the color of the desugared bamboo board was lighter, which was applicable to a wide range. Compared with carbonized bamboo board, the key mechanical properties of desugared bamboo board were significantly improved by 2 to 4 times. Under the same conditions, the anti-decay and anti-mildew properties of d desugared bamboo board were better than those of carbonized bamboo board as well. In conclusion, this study demonstrated the feasibility of hydrothermal desaccharification coupling for the preparation of outdoor reconstituted-bamboo-board.

Effect of alkali and alkaline earth metals on the liquefaction of lignocellulosic model compounds to prepare bio-oil in ethanol solvent

In this paper, glucose, xylan and lignin were selected as typical components of lignocellulosic biomass to conduct liquefaction experiments, and the effect of alkali and alkaline earth metals (AAEMs) on biomass liquefaction in ethanol was investigated. Alkaline earth metals (AEMs) had a positive catalytic effect on the yield and quality of xylan liquefied bio-oil, in particular, MgCl2 increased the yield of bio-oil from 26.6 wt% to 38.8 wt%. AAEMs inhibited the formation of glucose and lignin bio-oil, the yield of bio-oil was changed from lignin > glucose > xylan to lignin > xylan > glucose. AAEMs increased the content of ester compounds in bio-oil, inhibited the formation of long-chain aliphatic compounds, and promoted the transformation of macromolecular aromatic compounds into coke. The active catalytic sites of AAEMs were gradually covered by the adsorption of residues and carbon free radicals, blocking the active sites. The ability of carbon free radical to capture H source was weakened, and the transfer of active hydrogen to bio-oil was inhibited, which was not conducive to the improvement of higher heating value (HHV) of bio-oil.

Hydrothermal combined alkali pretreatment for fractionation the xylan from cotton stalk

Hydrothermal combined alkaline method was conducted to improve the yield of xylan from cotton stalk in this study. The extraction process was optimized by single factor and orthogonal experiments. The maximum yield of recovered xylan was 67.75 ± 0.27% obtaining from hydrothermal extraction of 170 ºC, 60 min, 1:10 and alkaline extraction with 4% alkali at 65 ºC for 2 h with S/L of 1:10. The physic-chemical properties of water-soluble xylan (Xwater) and alkali-soluble xylan (Xalkali) were determined by Fourier transform infrared spectroscopy, Gel permeation chromatography, thermogravimetric analysis and 2D nuclear magnetic resonance (2D NMR). The observed xylan was composed of (1→4)-β-d-xylp as main chain, β-glycosidic bond, and 4-O-methyl-α-D-glucuronic acid as branch chain. Xalkali also contains α-L-arabinose side chains. And the molecular weight of Xalkali was higher than that of Xwater, indicating that alkali pretreatment had a positive protective effect on xylan structure compared with hydrothermal pretreatment. The proposed combined pretreatment method has established a reliable xylan separation method, which has high industrial application feasibility.

A novel strategy for rapid identification of pyrolytic synergy and prediction of product yield: Insight into co-pyrolysis of xylan and polyethylene

The distributions of biomass and plastic co-pyrolysis products are complicated by abundant component combinations, pyrolysis conditions, and synergies. Herein, the hierarchical clustering analysis (HCA) and response surface methodology (RSM) were used to rapidly determine synergies and predict product yields of xylan and polyethylene (PE) co-pyrolysis at 500–700 °C. The results showed that co-pyrolysis promoted liquid production and suppressed solid and char formation. Pyrolytic interactions improved the decomposition of the PE-derived wax, resulting in 1.5–1.9- and 1.7–2.1-fold higher yields of heavy gas oil and C≥26 hydrocarbons compared to the theoretical values. HCA classified pyrolyzates with similar synergy into the same cluster, which reflected the suppressed carbonyl compound production, enhanced furfural and phenols yields at 700 °C, and greater C17–C30 hydrocarbon production. The quadratic model of RSM predicted the yields of gas, CO, C3Hn, C4Hn, liquid, ethanol, acetaldehyde, hydrocarbon oil, gasoline, solid, and char influenced by synergies. Owing to complex interactions, the cubic model fitted the CH4 and C2H4 yields. The linear model described the CO2 yield without synergy. This work illustrates the utility of combining RSM and HCA to predict product distributions of various waste co-treatment processes.

Optimizing yield and chemical compositions of dimethylsulfoxide-extracted birchwood xylan

Dimethylsulfoxide (DMSO) extraction is commonly used to study the chemical structures of original xylan in the plant cell wall, since the DMSO can preserve the original structure of the xylan as much as possible during the extracting process. In addition, the DMSO-extracted xylans have unique properties allowing their potential applications in emulsifying or filming materials. However, the yield of DMSO-extracted xylan is always low and the effects of different DMSO extraction conditions on the chemical compositions of xylan have not been fully studied, which greatly hinders its researches and applications. In this study, we have found that extensive delignification before DMSO extraction results in destruction of lignin-carbohydrate complex (LCC), leading to xylan yield and xylose unit content increased by up to 220% and 20%, respectively. Tert-butanol washing of the holocellulose can further increase the DMSO extracted xylan yield by ∼10%. The yield of xylan extracted by the DMSO at 80 °C for 7 h was obviously higher than that at room temperature for 3 d by 30%–40%. Thermal analysis showed that the xylans extracted at different conditions had thermal stability without obvious differences. The results indicate that the DMSO-extracted xylan with a high yield, a high purity and a high degree of acetylation can be extracted at a high delignification level, a high reaction temperature and a short reaction time. This study is of great significance for studying xylan structure-property relationships and promoting the applications of DMSO-extracted xylan.

Inhibitory effect of lignin on the hydrolysis of xylan by thermophilic and thermolabile GH11 xylanases

BackgroundEnzymatic hydrolysis of lignocellulosic biomass into platform sugars can be enhanced by the addition of accessory enzymes, such as xylanases. Lignin from steam pretreated biomasses is known to inhibit enzymes by non-productively binding enzymes and limiting access to cellulose. The effect of enzymatically isolated lignin on the hydrolysis of xylan by four glycoside hydrolase (GH) family 11 xylanases was studied. Two xylanases from the mesophilic Trichoderma reesei, TrXyn1, TrXyn2, and two forms of a thermostable metagenomic xylanase Xyl40 were compared.ResultsLignin isolated from steam pretreated spruce decreased the hydrolysis yields of xylan for all the xylanases at 40 and 50 °C. At elevated hydrolysis temperature of 50 °C, the least thermostable xylanase TrXyn1 was most inhibited by lignin and the most thermostable xylanase, the catalytic domain (CD) of Xyl40, was least inhibited by lignin. Enzyme activity and binding to lignin were studied after incubation of the xylanases with lignin for up to 24 h at 40 °C. All the studied xylanases bound to lignin, but the thermostable xylanases retained 22–39% of activity on the lignin surface for 24 h, whereas the mesophilic T. reesei xylanases become inactive. Removing of N-glycans from the catalytic domain of Xyl40 increased lignin inhibition in hydrolysis of xylan when compared to the glycosylated form. By comparing the 3D structures of these xylanases, features contributing to the increased thermal stability of Xyl40 were identified.ConclusionsHigh thermal stability of xylanases Xyl40 and Xyl40-CD enabled the enzymes to remain partially active on the lignin surface. N-glycosylation of the catalytic domain of Xyl40 increased the lignin tolerance of the enzyme. Thermostability of Xyl40 was most likely contributed by a disulphide bond and salt bridge in the N-terminal and α-helix regions.Graphical

Towards directional pyrolysis of xylan: Understanding the roles of alkali/alkaline earth metals and pyrolysis temperature

To identify the roles of alkali/alkaline earth metals (AAEM) and reaction temperature during pyrolysis of hemicellulose, the effects of AAEM doping on the pyrolysis behaviors, kinetics, and product yields of xylan at different pyrolysis temperatures were assessed. The results demonstrated that the yields of anhydrosugars from pyrolysis of xylan were dependent on the AAEM cations and their doping concentrations. Demineralization achieved the directional conversion of xylan into xylosan at 300 °C. The doping of even 0.05 mmol/g AAEM significantly suppressed their formation. The yields of xylosan from pyrolysis of xylan doped with different AAEM cations decreased in the following order: Mg2+<Ca2+<Na+<K+. The formation of light oxygenates from pyrolysis of xylan was determined by the pyrolysis temperature rather than the doping of AAEM. Elevating pyrolysis temperature significantly improved their yields whilst reducing the yields of anhydrosugars. Aromatics were only observed during the pyrolysis of xylan at 900 °C. Mg and Na exhibited higher catalytic activity for suppressing the formation of aromatics. Pyrolysis kinetic analysis showed that the doping of AAEM increased the activation energy for the pyrolysis of xylan. These findings suggest that pyrolysis of AAEM-free hemicellulose at low temperatures is the key to achieving directional pyrolysis of hemicellulose into anhydrosugars.

Green production of low-molecular-weight xylooligosaccharides from oil palm empty fruit bunch via integrated enzymatic polymerization and membrane separation for purification

For xylooligosaccharides (XOS) production from agricultural residues, highly concentrated xylan liquor (116 g/L) was produced by crushing an oil palm empty fruit bunch (EFB) via continuous hydrothermal treatment and subsequent membrane-based concentration on a pilot scale. The yield of xylan extracted from the raw EFB was 53.7%. To produce XOS with a low degree of polymerization, xylanase-catalyzed hydrolysis was performed and the sum of xylobiose and xylotriose to extracted xylan was 81.6% under lab-scale optimal conditions and 69.3% under pilot-scale conditions. In addition, the crude XOS could be purified through a novel approach involving enzyme-mediated radical polymerization and membrane-based separation, while minimizing XOS loss and waste generation. As a result, 50.2% of the total phenolic compounds in the crude XOS material could be polymerized and precipitated through peroxidase-catalyzed reactions, and an additional 22.6% were removed using the membrane. Furthermore, the amount of activated carbon consumed and the XOS recovery rate after phenolic compound removal via the adsorption method using activated carbon were evaluated and compared with the integrated enzyme-membrane purification results. Consequently, this study provides an ecofriendly biomass refinery process for low-molecular-weight XOS production and purification that produces few toxic substances and little waste.

Bioprocess development for production of xylooligosaccharides prebiotics from sugarcane bagasse with high bioactivity potential

The xylooligosaccharides (XOS, prebiotics) production from xylan extracted from sugarcane bagasse (SB) biomass was accomplished using an in-house produced xylosidase-free endoxylanase from an isolate Aspergillus flavus MG-7. Delignification of SB by sodium hypochlorite, and xylan extraction by coupled sodium hydroxide and thermal treatment were optimized for various process variables based on Design of Experiments (DoE) to achieve enhanced xylan yield (96.11%, w/w). The extracted xylan was analysed by Fouriertransform infrared spectroscopy and thermogravimetric analysis to evaluate its structural morphology, purity and thermal stability. Xylan hydrolysate obtained by endoxylanase was quantified for xylobiose (69.57%, w/w), xylotriose (13.17%) and xylotetrose (8.377%), and XOS were examined by 1H NMR. Growth-promoting potential of XOS was established for a probiotic Lactobacillus plantarum M-13 isolated from kalarei. XOS exhibited excellent bioactivity potential in terms of high positive prebiotic activity score, significant antioxidant activity and antibacterial activity. Efficient XOS production promises value-addition for biorefining of SB biomass.

OPTIMIZATION OF XYLAN EXTRACTION PROCESS FROM RICE STRAW FOR PRODUCTION OF AUTOHYDROLYSATES RICH IN PREBIOTIC XYLOOLIGOSACCHARIDES

Rice straw, an abundant agricultural waste, possesses immense potential to serve as renewable, eco-friendly and non-edible feedstock to generate value-added products. Therefore, the present study aimed to obtain prebiotic neutral xylooligosaccharides (XOS)-rich autohydrolysate from rice straw xylan. The central composite design of response surface methodology was employed to optimize the conditions for the alkaline extraction of xylan, i.e. NaOH concentration (6-14%, w/v), reaction time (1-3.5 h) and temperature (50-100 °C). Autohydrolysis of xylan was carried out at 121 °C and 15 psi for varied hydrolysis times (10, 25 and 40 min) and sulphuric acid concentrations (0.1, 0.5 and 1.0M) to obtain XOS-rich autohydrolysate. The optimum conditions were found to be as follows: 11.04% (w/v) NaOH, 3.126 h and 80.146 °C, so that the maximum xylan yield of 19.97% was predicted by the software. This value was quite close to the experimental yield of 19.4%, with 80.83% xylan being recovered per gram of rice straw. The best autohydrolysis treatment for xylan was found to be using 0.1M sulphuric acid for 10 min, which allowed 34.5% of 100 mg xylan to be depolymerized to produce neutral XOS (degree of polymerization up to 7), with xylose, xylobiose and xylotriose constituting 4.45, 10.14 and 7.83 mg, respectively. These autohydrolysates promoted higher growth of Lactobacillus rhamnosus and Lactobacillus casei than established prebiotic fructooligosaccharides. The study attempts to solve disposal issues of rice straw through production of XOS-rich autohydrolysates in demand on the global nutraceuticals market.

Sylfation of Birch Wood Xylan with Sulfamic Acid in 1,4-dioxane

Sulfation of birch wood xylan in 1,4-dioxane by sulfamic acid in the presence of urea at 90 and 100 °C was studied for the first time. The effect of the duration of xylan sulfation on the yield of xylan sulfates and the sulfur content in them was studied. It was found that the sulfur content in the obtained xylan sulfates increases from 12.5 to 17.5 wt% with an increase in the duration of sulfation from 2 to 4 hours. The structure of initial and sulfated xylan was studied by FTIR and NMR spectroscopy. The ease of purification of the obtained xylan sulfates from 1,4-dioxane in comparison with the purification of xylan sulfates obtained by sulfation in pyridine and N, N‑dimethylformamide is an advantage of the proposed method of xylan sulfation

Extraction of sugarcane bagasse arabinoxylan, integrated with enzymatic production of xylo-oligosaccharides and separation of cellulose

Sugarcane processing roughly generates 54 million tonnes sugarcane bagasse (SCB)/year, making SCB an important material for upgrading to value-added molecules. In this study, an integrated scheme was developed for separating xylan, lignin and cellulose, followed by production of xylo-oligosaccharides (XOS) from SCB. Xylan extraction conditions were screened in: (1) single extractions in NaOH (0.25, 0.5, or 1 M), 121 °C (1 bar), 30 and 60 min; (2) 3 × repeated extraction cycles in NaOH (1 or 2 M), 121 °C (1 bar), 30 and 60 min or (3) pressurized liquid extractions (PLE), 100 bar, at low alkalinity (0–0.1 M NaOH) in the time and temperature range 10–30 min and 50–150 °C. Higher concentration of alkali (2 M NaOH) increased the xylan yield and resulted in higher apparent molecular weight of the xylan polymer (212 kDa using 1 and 2 M NaOH, vs 47 kDa using 0.5 M NaOH), but decreased the substituent sugar content. Repeated extraction at 2 M NaOH, 121 °C, 60 min solubilized both xylan (85.6% of the SCB xylan), and lignin (84.1% of the lignin), and left cellulose of high purity (95.8%) in the residuals. Solubilized xylan was separated from lignin by precipitation, and a polymer with β-1,4-linked xylose backbone substituted by arabinose and glucuronic acids was confirmed by FT-IR and monosaccharide analysis. XOS yield in subsequent hydrolysis by endo-xylanases (from glycoside hydrolase family 10 or 11) was dependent on extraction conditions, and was highest using xylan extracted by 0.5 M NaOH, (42.3%, using Xyn10A from Bacillus halodurans), with xylobiose and xylotriose as main products. The present study shows successful separation of SCB xylan, lignin, and cellulose. High concentration of alkali, resulted in xylan with lower degree of substitution (especially reduced arabinosylation), while high pressure (using PLE), released more lignin than xylan. Enzymatic hydrolysis was more efficient using xylan extracted at lower alkaline strength and less efficient using xylan obtained by PLE and 2 M NaOH, which may be a consequence of polymer aggregation, via remaining lignin interactions.

MATHEMATICAL OPTIMIZATION OF THE PROCESS OF BIRCH WOOD XYLAN SULFATION BY SULFAMIC ACID IN N, N-DIMETHYLFORMAMIDE MEDIUM

The effect of temperature and duration of sulfation of birch wood xylan by sulfamic acid in N, N-dimethylformamide (DMF) medium in the presence of urea on the yield of sulfated xylan and on the sulphur content was studied. By mathematical optimization, the sulfation conditions have been established allowing to achieve a high yield of the obtained xylan sulfates with a high sulphur content. Under optimal sulfation conditions: temperature 100±3 °C, duration 1.5 hours, the yield of sulfated xylan reaches to 63% mas. and the content of sulfur – 17.6% mas. The presence of sulfate groups in sulfated xylan samples obtained under optimal conditions was confirmed by elemental analysis and FTIR and 13C NMR spectroscopy.

Synergistic effects of biomass building blocks on pyrolysis gas and bio-oil formation

Before biobased fuels can replace fossil fuels, several key issues must be addressed. Bio-oils derived through pyrolysis of lignocellulosic material have high acidity and viscosity, and poor energy density and stability. To address these issues, this paper examines the individual and combined behavior of lignocellulosic feedstock components to shed light on the potential to generate preferential biofuel properties through biomass mixing. Dry lignocellulosic biomass is mostly composed of cell wall polysaccharides (cellulose, hemicellulose, lignin), which vary widely in type and concentration across biomasses. This heterogeneity leads to increased unpredictability in biobased fuel formation during pyrolysis. Using derivative thermogravimetric (DTG) analysis, gas chromatography-mass spectroscopy, and residual gas analysis, this work explores the synergistic interactions of lignocellulosic biomass components during pyrolysis to manipulate bio-oil and gas product composition based on desired compound classes. Cellulose, xylose, xylan, and lignin were blended at different ratios to determine the extent of synergistic effects during pyrolysis. For each mixture, an ‘expected’ outcome was developed by summing the individual behavior (e.g. mass loss rate, H2 gas evolution, etc.) of the individual components based on mass fraction present. Mixtures containing lignin and/or xylan yield peak DTG mass loss rates at lower temperatures than predicted with corresponding reductions in biochar yield suggesting synergistic interactions that promote devolatilization. By itself, lignin produces large amounts of hydrogen gas, and when mixed with other biomasses promotes dehydrogenation. Lignin increases CO2 formation, resulting in lower oxygen concentrations in the bio-oil and biochar. While suppressing bio-oil generation, the presence of lignin – even at low concentrations – increases the number of phenol compounds produced, while decreasing the yield of furans. The synergistic interactions between different polysaccharides could be exploited depending on the desired biorefinery products – allowing for targeted selection of lignocellulosic biomass mixes to fine-tune resulting fuels.

Preparation and characterization of xylan by an efficient approach with mechanical pretreatments

Corn stalks, as an agricultural biomass resource, were generally burned or discarded, which not only leads to environmental pollution but also a waste of resources. To study the high-value use of resources, the extraction of xylan from corn stalks was carried out in this investigation. First, mechanical pretreatment was developed to change the internal structure of raw materials. And then the alkali-extractable xylan was isolated by a P-E method (adjusting the pH of the hydrolysate to separate lignin first, and then add ethanol to precipitate xylan). From the SEM, XRD, and sugar analysis, it was shown that the pretreatment materials with a more obvious displacement of fiber and lower crystallinity were easier to be hydrolyzed. And over 85 % xylan and about 80 % lignin could be removed from corn stalks under a lower alkali concentration. Besides, the yield of xylan increased from 45.80 % to 80.60 % by different mechanical pretreatment means. The structural properties of xylan were characterized by Ion Chromatography, FT-IR, thermo-gravimetric analysis, molecular weights, and NMR. Results proved that xylan had a backbone of d-xylp with a β-(1→4)-linkage attached with α-l-Araf and 4-O-Me-α-d-GlcpA. This work introduced a physic-chemical xylan extraction route from corn stalks, which is promising in the biorefinery process.

Production of xylo-oligosaccharides from wheat straw using microwave assisted deep eutectic solvent pretreatment

This study aimed to investigate the effect of microwave assisted deep eutectic solvent (MW-DES) pretreatment on the solubilization of xylan and release of xylo-oligosaccharides (XOS) from wheat straw. The samples were treated with choline chloride: formic acid at different microwave powers (209–594 W) and pretreatment times (10–120 s). The corresponding microwave energy applied to the samples was calculated in the range of 466–1965 J/g. The xylan yield in the solid fraction decreased almost linearly with an increase in microwave energy. The xylose monomer and oligosaccharide yields in the liquid fraction first increased with the microwave energy applied and then declined. The highest xylose monomer and total xylo-oligosaccharide yield (observed at 209 W, 80 s (1309 J/s)) were 20 % and 32 % (13.6 and 72.7 g/kg wheat straw), respectively. HPAEC-PAD analysis revealed that XOS with a degree of polymerization (DP) below 6 comprised 43 % of the total XOS at this condition. Increase in solvent amount (from 1:10 to 1:15 g:mL) improved the xylo-oligosaccharide yields only by 14 %. Approximately 68 % reduction in furfural yield was achieved with 5 % water addition in deep eutectic solvent.