Xylan Extraction Research Articles

Use of corn cob through xylan extraction and its potential use as a substrate for the quantification of xylanase enzymatic activity

In Mexico, it is estimated that the amount of residues produced by the planting of the ten main crops is approximately 45 million tons of dry matter, of which just over 25 million tons are corn cob. The corn cob contains large amounts of hemicellulose, mainly composed of xylan, which can have various industrial uses. For this reason, in the present study, fresh and dry corn cob was used with two particle sizes: 0.105 mm and 0.42 mm, to carry out an exhaustive alkaline extraction of xylan and where eight fractions of hemicelluloses extracts were obtained. Each of the fractions were subjected to enzymatic hydrolysis for eight hours with a commercial xylanase (Livanol Devisco 1500) and as internal control, beechwood xylan (Sigma Aldrich, X4252) was used, of which only 6.9 ± 2.25 g/L were released. reducing sugars. It was found that the fractions from the steam treatment and the fraction from the alkaline extraction precipitated with alcohol, both for fresh corn cob, were released a quantity of reducing sugars very similar to commercial xylan with 7.10 ± 2.02 and 7.24 ± 0.37 g/L, respectively. Finally, it was possible to determine that although the 8 fractions obtained in the present study can be used as substrates to determine the xylanase enzymatic activity, the best was the fraction of the alkaline extraction since 0.236 ± 0.03 IU/mL were quantified, while for the commercial substrate (beechwood xylan) an activity of 0.287 ± 0.01 IU/mL was obtained.

Pectin-associated mannans and xylans play distinct roles in cell-cell adhesion in pine and poplar wood

Wood particles of pine required longer treatments of acidic chlorite and dilute alkali to achieve similar proportions of cell separation as of poplar. Chemical extraction and enzymatic digestion studies indicated that rhamnogalacturonan-I (RG-I), mannan and xylan contribute to cell-cell adhesion in pine wood. Mannan associated with lignin in an acidic chlorite fraction and with xylan in a dilute alkali fraction. RG-I and xylan were extracted in both chlorite and dilute alkali in poplar. Scanning electron microscopy and a probe diffusion study using Fluorescence Recovery After Photobleaching showed that lignin, RG-I and mannan initiated cell separation at cell corners and dilute alkali extraction of xylan was required for complete cell separation in pine. Cell-cell separation increased enzymatic saccharification within 24 h by 2-fold in poplar and 3.4-fold in pine. Our results inform a strategy to reduce particle size in woody biomass and provide insights into different molecular bases of cell-cell adhesion.

PH graded lignin obtained from the by-product of extraction xylan as an adsorbent

As an important agricultural residue, corn stalks have been continuously used in various industries. In this work, lignin, the by-product of xylan extraction from corn stalks, was used as a useful adsorbent for the removal of methylene blue from aqueous solutions. Lignins were precipitated from the hydrolysates of pH 3 (LG3) and 5 (LG5), hoping to explore the difference in adsorption performance between the two. Detailed discussions were performed to provide a firm evaluation of adsorption models followed by batch experiments to analyze the methylene blue adsorption performance. Results showed that the lignin obtained at pH 5 had a better adsorption capacity compared with pH 3, which was mainly caused by the difference in specific surface area. When the optimal adsorption conditions (pH: 10; temperature: 35 °C; adsorption time: 90 min) were achieved, the maximum adsorption capacity of LG5 can reach 134.3 mg/g, which was much higher than those of most unmodified lignins extracted from other biomass energy sources. Regarding the adsorption behavior, the adsorption data were fitted by pseudo-second-order kinetics model and the isotherm adsorption equilibrium followed the Langmuir model. Overall, these results indicate that lignin, the by-product of xylan extraction, offers a great potential for removing methylene blue from wastewater.

Xylan extraction strategies and the performance of the resulting high purity cellulose fiber to swelling and dissolution

In this study, we investigated the influence of hemicelluloses removal treatment on the reactivity of the resulting pulp. The idea was to develop treatment strategies consisting of mechanical refining (different refining technologies), chemical treatment (CCE), and xylanase treatment that enabled both quantitative xylan removal as well as good reactivity to dissolution without the need for additional post-extraction treatments (cellulose activation) to improve reactivity. Cellulose post-extraction treatments result in additional production costs. The reactivity of the extracted pulps was evaluated based on the degree of swelling in NaOH and dilute cupriethylene diamine solution (CUEN), the solubility in 8% NaOH at -10 °C, and the Fock reactivity. The result obtained showed that hemicelluloses removal strategies that included mechanical refining treatment led to better pulp reactivity than unrefined pulp. The best result was obtained with refined pulp extracted with 6% soda (cellulose II not detected). In addition, we obtained a Fock reactivity ranging from 60 to 70%. The good correlations found between fiber swelling, solubility in caustic soda, and Fock reactivity suggest that the tedious Fock test could be substituted by the much simpler swelling and solubility measurements. The negative impact of cellulose II on pulp reactivity is due to the higher number of hydrogen bonds formed under dewatering and drying. This problem would most likely be averted in the ideal case where pulp dissolution is integrated into the pulp mill.

TEMPERATURE AND PH OPTIMIZATION OF CAR THERMOPHILIC BACTERIA FOR THE PRODUCTION OF XILANASE THE BLEACHING OF ENVIRONMENTALLY FRIENDLY INKED PAPER WASTE

Xylanase is an extracellular enzyme capable of hydrolyzing hemicellulose so that it can convert xylan into xylose. Xylanase enzymes can be used in the pulp and paper industry. This study aims to determine the effect of temperature, pH on enzyme production by immobilized thermophilic bacteria using rice straw xylan extract as a substrate and to see the effect of xylanase administration on the whiteness level of inked paper waste. This study was an experimental study and used a completely randomized design (CRD). Enzyme activity was measured using a spectrophotometer at a wavelength of 540 nm. Enzyme activity data were analyzed using the ANOVA test and continued with the DMRT (Duncan Multiple Range Test) further test with a level of 5% and the whiteness of the paper was determined by testing the kappa number. The results obtained were that the temperature of immobilize thermophilic bacteria using rice straw xylan extract as a substrate affected the xylanase enzyme activity with an optimum temperature of 75°C having the highest average value of enzyme activity 4.668 U/mL. Meanwhile, the optimum pH for immobilized thermophilic bacteria to produce xylanase was pH 8.5 with the highest average value of enzyme activity 4.854 U/mL. The addition of xylanase enzyme in the fermentation process of inked paper waste was able to increase the brightness of the inked paper with a lower average value of kappa number of 2.762 compared to the higher control of 5.525.

Effect of pretreatments on production of xylooligosaccharides and monosaccharides from corncob by a two-step hydrolysis

Xylan extraction by alkali is usually a prerequisite for traditional xylooligosaccharide (XOS) production from corncob. In this study, to avoid xylan isolation before XOS production, corncob was delignified by hydrogen peroxide-acetic acid (HPAA), followed by a two-step enzymatic hydrolysis for XOS and monosaccharide production. High lignin removal (55.5%–82.6%) was observed upon pretreatment with 75%–100% HPAA and using 50–100 mM H2SO4 as a catalyst. A high XOS yield of 27.8% was obtained from 75% HPAA-pretreated corncob with 75 mM H2SO4, and the xylose/XOS ratio was only 0.09, indicating that the purity of XOS was relatively high. The highest glucose yield (79.1%) was obtained from 100% HPAA-pretreated corncob with 50 mM H2SO4. Finally, 58.3 g of XOS, 186.9 g of glucose, and 56.4 g of xylose were obtained from 1 kg of corncob. This study provides a promising approach for XOS and monosaccharide production from corncob without xylan isolation.

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.

Optimized production of xylooligosaccharides from poplar: A biorefinery strategy with sequential acetic acid/sodium acetate hydrolysis followed by xylanase hydrolysis

The preparation of xylooligosaccharides (XOS) from lignocelluloses by organic acid hydrolysis has the advantages of high efficiency and simplicity, but reducing the production of by-products, especially xylose, is a prerequisite for commercial preparation of XOS using organic acid. In this work, to reduce the production of by-products, the acetic acid/sodium acetate conjugate system (AC/SA) was used to prepare XOS from poplar. Under the optimal conditions (0.15 M AC/SA, molar ratio of 3.0, 175 °C, 60 min), the maximum XOS yield was 33.6% with a low xylose/XOS ratio of 0.19. Xylanase hydrolysis effectively converted XOS with DP above 6 in the AC/SA hydrolysate to X2-X6 with little xylose produced. The XOS yield increased to 42.1%, with a xylose/XOS ratio was only 0.17. This work shows that AC/SA in combination with xylanase hydrolysis of poplar successfully achieved high XOS yield with low by-products yields without the extraction of xylan from the substrate.

Comparative evaluation of xylan extraction methods and product characterization from sugarcane bagasse

Comparative evaluation of xylan extraction methods and product characterization from sugarcane bagasse

Influence of Hollander beater refining on xylan extraction from hardwood paper pulp by cold caustic extraction and xylanase treatment

Cellulose fibers’ complex and compact structure hinders the quantitative extraction of residual hemicelluloses from the fiber wall. In this study, hardwood kraft paper pulp was subjected to refining with a Hollander beater at different refining loads (3, 4.5, and 5.5 kg) in order to assess the impact of refining load on xylan removal by cold caustic extraction. The refined pulp showed high water retention values and specific surface area, which increased accessibility and a correspondingly high degree of xylan removal. Coupling refining and cold caustic extraction (100 g/L soda) achieved over 50% more xylan removal than the unrefined pulp (3% against 7%, respectively). Furthermore, an improvement in xylan removal (79%) was achieved by implementing a one-pot simultaneous refining and cold caustic extraction treatment at half the time required for the sequential treatment and low soda concentration (60 g/L). Finally, the benefit of beating was also observed for xylanase treatment. Overall, the combined extractions made it possible to remove 85% of xylan from a conventional hardwood paper pulp giving rise to a high purity cellulose pulp with unimodal and narrow molecular mass distribution.

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.

Xylitol Production from Sugarcane Bagasse Through Ultrasound-Assisted Alkaline Pretreatment and Enzymatic Hydrolysis Followed by Fermentation

This study focused on the optimization of xylitol production from sugarcane bagasse by using response surface methodology. Xylitol was produced through a series of processes, firstly, optimization of ultrasound-assisted mild alkaline pretreatment for the xylan extraction from sugarcane bagasse followed by enzymatic hydrolysis of xylan to xylose by enzyme β-1,4-xylanase and finally microbial fermentation of xylose to xylitol using yeast (Candida guilliermondii), bacteria (Corynebacterium glutamicum) and their mixed culture for different time periods (0–96 h). Maximum xylan recovery of 12.059% (w/w) was observed at pretreatment; 0.73 M NaOH, 1:38.55 solid-to-liquid ratio and 34.77 min ultrasonication. The enzyme concentration of 400 U/g xylan at 48 h of incubation showed the highest xylose production (81.51 mg/g bagasse). Yeast (C. guilliermondii) resulted in the highest xylitol yield (Yp/s = 0.43 g/g) after 72 h. This bioprocess route can contribute as a suitable alternative for chemical methods of xylitol production.

Characteristics of sugarcane bagasse fibers after xylan extraction and their high-solid hydrolysis cellulase-catalyzed

The enzymatic hydrolysis of sugarcane bagasse to obtain a high efficiency conversion of polysaccharides in monosaccharides is dependent on factors related to the morphology and chemical composition. Therefore, a pre-treatment step is necessary to obtain a less recalcitrant substrate. Here, alkaline sulfite with ethanol (ASE) was employed to pretreat sugarcane bagasse aiming to produce substrates enriched in carbohydrates with greater cellulose accessibility. A xylanase stage was evaluated as a strategy to remove arabinoxylan fraction from pretreated bagasse and to verify the influence of the addition of the enzyme xylanase (5, 50, and 500 IU/g material) on the characteristics of ASE pretreated bagasse from 5 to 15% dry matter. The highest xylan extraction yield of 59% was achieved when working at 15% solids and xylanase dosage of 500 IU/g substrate. The interaction of enzyme and solid loadings was positive to arabinoxylan extraction, however the excessive removal of arabinoxylans caused changes on biomass fiber surface and a decrease in water absorption. The cellulase-catalyzed hydrolysis of ASE bagasse ASE pre-extracted by xylanase was nearly paralleled to the control sample, at 15% solids. This study shows that the enzymatic removal of xylan from pretreated bagasse provides a promising condition for the generation of the value-added product in the biorefinery process.

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.

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.

Understanding the conformational change and inhibition of hyperthermophilic GH10 xylanase in ionic liquid

Xylan is an abundant hemicellulosic feedstock of pentose sugars present in the Lignocellulose biomass, offering massive potential for the generation of biofuel and numerous value-added by-products. The extraction of xylan is a major challenge due to the typical organization of cellulose, hemicellulose and lignin. Ionic Liquid (IL) is a promising solvent for the deconstruction of the complex lignocellulosic structure. However, the residual IL present in the pretreated xylan significantly affects xylanase activity during the hydrolysis. Thus, a molecular understanding focusing on the IL-xylanase interaction needs to be explored for developing IL tolerant xylanases for efficient xylan hydrolysis. In this study, atomistic molecular dynamics (MD) simulations were performed to investigate the IL tolerance of hyperthermophilic GH10B xylanase from Thermotoga maritima (TmXYN10B) in both aqueous and water/1-Ethyl-3-methylimidazolium acetate (EmimAc) binary solvent systems. The enzyme was stable in all solvents at high temperature (363 K). However, the opening and closing motions of the xylanase were lost in high EmimAc concentration. Besides, the formation of a considerable number of hydrogen bonds between acetate anion and amino acids at the enzyme surface might change its native motion in high EmimAc system. The IL induced conformational change was charecterized by constructing Protein Structure Network (PSN) on each snapshot from the MD simulation trajectory. Here we captured the enzyme conformational change by identifying disjoint cliques and communities at the active site in high EmimAc concentration. Furthermore, Emim cations populated the active site with higher binding occupancy and suggested to inhibit the enzymatic hydrolysis. Finally, this study provides a theoretical understanding of the reduced activity of the TmXYN10B xylanase in IL, which can pave the path for engineering xylanases for biofuel production.

Extraction and characterization of xylan from sugarcane tops as a potential commercial substrate

Xylan is the major hemicellulose present in sugarcane stem secondary cell walls. Xylan is composed of xylose backbone with a high degree of substitutions, which affects its properties. In the present study, the xylan from sugarcane tops (SCT) was extracted and characterized. Compositional analysis of xylan extracted from SCT (SCTx) displayed the presence of 74% of d-xylose residues, 16% of d-glucuronic acid residues and 10% of l-arabinose. High performance size exclusion chromatographic analysis of SCTx displayed a single peak corresponding to a molecular mass of ∼57kDa. The Fourier transform infrared spectroscopic analysis of SCTx displayed the peaks corresponding to those obtained from commercial xylan. FESEM analysis of SCTx showed the granular and porous surface structure. Differential thermogravimetric analysis (DTG) of SCTx displayed two thermal degradation temperatures (Td) of 228°C, due to breakdown of the side chains of glucuronic acid and arabinose and 275°C, due to breakdown of xylan back bone. The presence of arabinose and glucuronic acid as a side chains was confirmed by the DTG and thermogravimetric analysis. The CHNS analysis of SCTx showed the presence of only carbon and hydrogen supporting its purity. The recombinant xylanase (CtXyn11A) from Clostridium thermocellum displayed a specific activity of 1394±51U/mg with SCTx, which was higher than those with commercial xylans. The thin layer chromatography and electrospray ionization mass spectroscopy analyses of CtXyn11A hydrolysed SCTx contained a series of linear xylo-oligosaccharides ranging from degree of polymerization 2-6 and no substituted xylo-oligosaccharides because of the endolytic activity of enzyme. The extracted xylan from SCT can be used as an alternative commercial substrate and for oligo-saccharide production.

Anatomic influence of sugarcane biomass on xylan solubilization

Sugarcane biomasses, such as bagasse and straw, are abundant and represent renewable sources for the production of molecules of economic interest, such as xylan. However, the solubilization methods for this macromolecule face the material recalcitrance and, consequently, need a higher amount of chemicals. This study brings as the fractioning of biomass for xylan extraction, aiming to verify how the recalcitrance of different segments of the plant may interfere with the process of xylan solubilization. Hydrogen peroxide was applied in the xylan solubilization starting from the bagasse, moving on to the leaf and stem, which was fractionated in internode, node, and external fraction (which contains epidermis). The solubilized xylan was evaluated as a substrate for the determination of the enzymatic activity of xylanase. The solubilized xylan was monitored for its solubility and for impurities, such as salt and residual lignin content. The results of xylan solubilization with 6 % of hydrogen peroxide were 86.28, 65.39, 76.78, 97.95, 96.48 %, successively for bagasse, internode, node, external fraction, and leaf. With the application of 3% peroxide, the yield decreased to lower than 30 %, except for the internode and the leaf, which showed 47.85 and 46.15 %, respectively. The RMN analysis suggested similarity among the xylan samples solubilized from the different sugarcane anatomic fractions. The highest enzymatic activities were found with the solubilized xylan, instead of the commercial one. The solubility and purity tests (low salt content) indicate that the solubilized xylan presented characteristics similar to commercial xylan or even better than it.

Evaluation of Xylooligosaccharides Production for a Specific Degree of Polymerization by Liquid Hot Water Treatment of Tropical Hardwood.

Eucalyptus pellita is known as attractive biomass, and it has been utilized for eucalyptus oil, furniture, and pulp and paper production that causes a significant amount of byproducts. Liquid hot water treatment depending on combined severity factor (CSF) was subjected to isolate hemicellulose fraction from E. pellita and to produce xylooligosaccharides (XOS). The xylan extraction ratio based on the initial xylan content of the feedstock was maximized up to 77.6% at 170 °C for 50 min condition (CSF: 1.0), which had accounted for XOS purity of 76.5% based on the total sugar content of the liquid hydrolysate. In this condition, the sum of xylobiose, xylotriose, and xylotetraose which has a low degree of polymerization (DP) of 2 to 4 was determined as 80.6% of the total XOS. The highest XOS production score established using parameters including the xylan extraction ratio, XOS purity, and low DP XOS ratio was 5.7 at CSF 1.0 condition. XOS production score evaluated using the CSF is expected to be used as a productivity indicator of XOS in the industry (R-squared value: 0.92).

Integration of hemicellulose pre-extraction and solid alkali-oxygen cooking processes for lignocellulose fractionation with emphasis on xylan valorization

Cooking with active oxygen and solid alkali (CAOSA) is a mild and environmentally friendly method for separation of lignin components. The degradation mechanism of hemicellulose associated with this method has been investigated. It was found that the hemicellulose-derived polysaccharides were directly oxidized rather than hydrolyzed to monosaccharides for degradation. To avoid the undesirable degradation of hemicellulose components by CAOSA, the idea of separating hemicellulose first in the form of xylan to produce xylooligosaccharide was presented by this study. Although hydrothermal autocatalysis has been commonly used in hemicellulose separation, the effects of acid-enhanced hydrothermal method and alkali-suppressed hydrothermal method on hydrothermal autocatalysis were systematically compared for the first time, and it was found that the acid-enhanced method was beneficial for highly selective extraction of xylan. Then, the hemicellulose-removed bamboo was treated with CAOSA process to separate lignin from cellulose. It was found that solid alkali dosage of CAOSA could be evidently decreased for hemicellulose-removed bamboo, which was helpful to reduce the cost of CAOSA. Coupling hemicellulose pre-extraction and CAOSA lignin fractionation strategy, a comprehensive biorefinery case for bamboo biomass could be anticipated.