Solubility Of Xylan Research Articles

Molecular scale behavior of xylan during solvent-controlled extraction and precipitation.

Solvent-controlled extraction and precipitation are the most fundamental methods for obtaining hemicellulose from lignocellulosic biomass and purification processes. However, the dissolution and precipitation mechanisms involved have scarcely been mentioned. In this study, the molecular scale behavior of xylan-type hemicellulose during solvent-controlled extraction and precipitation is investigated using molecular dynamics (MD) simulations and density functional theory (DFT) calculations. To bring the model closer to the real extracted xylan, a high degree of polymerization (DP100) of xylan is established, and hemicelluloses with low DP (DP15 and DP50) are also investigated. Four phenomena are explained at the molecular level, including the influence of the polymerization degree and side chain on the solubility of xylan in water, the improvement of the xylan's solubility in NaOH, the precipitation of xylan in ethanol, and the acetyl group preservation of xylan in DMSO. This study contributes to an increased understanding of the dissolution and precipitation mechanisms of hemicellulose and provides a resource for the simulation of high DP hemicellulose, which gives a theoretical basis for the efficient extraction of high-purity hemicellulose as well as economic biorefining.

Probing the mechanism of green solvent solubilization of hemicellulose based on molecular dynamics simulations

Extraction and solubilization of hemicellulose based on green solvents has become a technological hotspot affecting the efficient utilization of hemicellulose. In this paper, the solubilization effect of three ionic liquids and three choline chloride-based deep eutectic solvents for xylan was studied using molecular dynamics method. The solubility of xylan could reach 15 wt% in all six solvents and glucuronic acid xylan was the most soluble. Based on DFT calculations and molecular dynamics simulations, it was concluded that the solubilization mechanisms of the two green solvents were similar and were based on the strong hydrogen bond between the anion and the hydroxyl group on the xylan model. The ionic liquids with [CH3COO]- and choline chloride/urea (1:2) showed excellent solubilization results. The results showed that the hydrogen bonding network and strength increased with the increase of urea content. Meanwhile the addition of water formed a new choline chloride/urea (1:2)-water hydrogen bonding network, which enhanced the interaction of xylan with choline chloride/urea (1:2) and promoted dissolution.

Novel, recyclable Brønsted acidic deep eutectic solvent for mild fractionation of hemicelluloses

Acidic deep eutectic solvents (DESs) are promising media for lignin valorization and cellulose conversion due to their good ability in efficient deconstruction of plant cell wall. However, hemicellulose extraction from lignocellulose using acidic DESs remains a challenge. Herein, novel and green Brønsted acidic DESs (BDESs) were synthesized from natural organic acids and common polyols and successively adopted to deconstruct corncob for mild fractionation of hemicelluloses. Oxalic acid (OA)-based BDESs were preferred for corncob processing due to the high solubility of xylan. The results revealed that the suitable acidity of DESs and mild temperature effectively avoided the over-degradation of hemicelluloses. The chemical composition and structural features of the recovered hemicelluloses were investigated systematically. Moreover, after ethylene glycol (EG)-OA BDES was recycled and reused three times, the extraction still resulted in a satisfactory hemicellulose yield. The novel and eco-friendly processing offers a practical and sustainable route for hemicellulose extraction in acidic condition.

Highly efficient dissolution of xylan in ionic liquid-based deep eutectic solvents

Development of efficient solvents to dissolve lignocellulose and its main components is of significant importance for the utilization/transformation of lignocellulose. Herein, several ionic liquid (IL)-based deep eutectic solvents (DESs) were prepared using four ILs as the hydrogen bond acceptors and four different hydrogen bond donors, including thiourea (TU), N-methylthiourea (NMTU), glycerol (Gly), and ethylene glycol (EG). Using the dissolution of xylan (a typical type of hemicellulose) as the example, it was observed that the synthesized IL-based DESs could efficiently dissolve xylan. Especially in the DES formed from 1-allyl-3-methylimidazolium chloride and EG, the xylan solubility could reach as high as 40.4 wt% at 343.15 K. More importantly, the solubility of xylan in IL-based DESs was much higher than that in the corresponding IL. The enhancement effect might be ascribed to that the formation of DESs could significantly decrease the viscosity and increase the hydrogen bond accepting ability. Additionally, the regeneration of the xylan from the DESs could be easily realized using ethanol as the anti-solvent, and the regenerated xylan kept a high consistency with the original xylan. Ionic liquid-based deep eutectic solvents were designed for highly efficient dissolution of xylan owing to the decreased viscosity and the increased hydrogen-bond accepting ability.

Enzymatic production of 4-O-methyl d-glucaric acid from hardwood xylan

BackgroundDicarboxylic acids offer several applications in detergent builder and biopolymer fields. One of these acids, 4-O-methyl d-glucaric acid, could potentially be produced from glucuronoxylans, which are a comparatively underused fraction of wood and agricultural biorefineries.ResultsAccordingly, an enzymatic pathway was developed that combines AxyAgu115A, a GH115 α-glucuronidase from Amphibacillus xylanus, and GOOX, an AA7 gluco-oligosaccharide oxidase from Sarocladium strictum, to produce this bio-based chemical from glucuronoxylan. AxyAgu115A was able to release almost all 4-O-methyl d-glucuronic acid from glucuronoxylan while a GOOX variant, GOOX-Y300A, could convert 4-O-methyl d-glucuronic acid to the corresponding glucaric acid at a yield of 62%. Both enzymes worked effectively at alkaline conditions that increase xylan solubility. Given the sensitivity of AxyAgu115A to hydrogen peroxide and optimal performance of GOOX-Y300A at substrate concentrations above 20 mM, the two-step enzyme pathway was demonstrated as a sequential, one-pot reaction. Additionally, the resulting xylan was easily recovered from the one-pot reaction, and it was enzymatically hydrolysable.ConclusionsThe pathway in this study requires only two enzymes while avoiding a supplementation of costly cofactors. This cell-free approach provides a new strategy to make use of the underutilized hemicellulose stream from wood and agricultural biorefineries.

Natural Xilan Production From Corncobs (Zea Mays L.) With Extraction Method

Corn (Zea mays L.) not only used as food by humans, however also used for animal feed and industrial materials but in part of corncobs still untapped, corncobs is a lignocellulosic material with 38,99% fiber which contain the highest xilan (12,4%) comparedwithotheragriculturalwaste.Theobjectiveofthisresearchwastogetxylan fromcorncobswithextractionmethod.Xylanextractionfromcorncobsweredoneintwo steps, firstly delignification process in NaOCl with concentration 0,5 on temperature 28∘C, solids which resulting from immersion in NaOH solution with concentration 5%, 10%, 15%, and 20% for 24 hours with temperature 20, 40, and 70∘C.the resulting of filtrate were neutralized with HCL 6N, futhermore centrifuge during 30 minute with 4000 rpm. Water soluble xylan can separated with ethanol 95% with ratio supernatan and ethanol 1:3, yielding 12.9% of xylan. The solubility of xylan produced with alkali (NaOH 1%), HCl 1N, ethanol, in cold and hot water was observed. Quantitative and qualitative analysis of xylan were done using HPLC by measuring retention time. The instrumen used with HPLC Shimadzu C-R3A, C18 column type, water mobile phase, Refractive index detector with flow rate 0,8 ml/minute result showed with purity 96%.

Per-O-acylation of xylan at room temperature in dimethylsulfoxide/N-methylimidazole

The per-O-acylation of xylan-type hemicellulose was firstly carried out in dimethylsulfoxide/N-methylimidazole (DMSO/NMI) at room temperature without additional catalyst. The optimum conditions for esterification of xylan was investigated in terms of the molar ratio of reagents to anhydroxylose units (AXU) in xylan and the kinds of esterification reagents to obtain a high degree of substitution (DS, 1.98) and weight percent gain (WPG, 86.88 %) of xylan esters. In this solvent system, NMI acted as a solvent, a base and an excellent catalyst, therefore, the per-O-acylation of xylan (DS of 1.98) was readily accomplished in DMSO/NMI system at room temperature. Structure elucidation of xylan esters was characterized by FT-IR and NMR (1H-NMR, 13C-NMR and HSQC). FT-IR and NMR analyses provided the direct evidence of per-O-acylation of xylan under the given conditions. Furthermore, HSQC revealed the higher reactivity of hydroxyls at C-2 position than those at C-3 position of xylan. The solubility of xylan in DMSO, DMF and CHCl3 improved after esterification. TGA/DTG indicated that the thermal stability of xylan increased after the esterification with anhydrides, while decreased with acyl chlorides, probably due to degradation and hydrolysis of the acylated xylan at the presence of by-product hydrochloric acid.

Dual-Component System Dimethyl Sulfoxide/LiCl as a Solvent and Catalyst for Homogeneous Ring-Opening Grafted Polymerization of ε-Caprolactone onto Xylan

The preparation of xylan-graft-poly(ε-caprolactone) (xylan-g-PCL) copolymers was investigated by homogeneous ring-opening polymerization (ROP) in a dual-component system containing Lewis base LiCl and strong polar aprotic solvent dimethyl sulfoxide (DMSO). DMSO/LiCl acted as solvent, base, and catalyst for the ROP reaction. The effects of the parameters, including the reaction temperature, molar ratio of ε-caprolactone (ε-CL) to anhydroxylose units (AXU) in xylan, and reaction time, on the degree of substitution (DS) and weight percent of PCL side chain (WPCL) were investigated. The results showed that xylan-g-PCL copolymers with low DS in the range of 0.03-0.39 were obtained under the given conditions. The Fourier transform infrared spectroscopy (FTIR), (1)H nuclear magnetic resonance (NMR), (13)C NMR, (1)H-(1)H correlation spectroscopy (COSY), and (1)H-(13)C correlation two-dimensional (2D) NMR [heteronuclear single-quantum coherence (HSQC)] characterization provided more evidence of the attachment of side chains onto xylan. Only one ε-CL was confirmed to be attached onto xylan with each side chain. Integration of resonances assigned to the substituted C2 and C3 in the HSQC spectrum also indicated 69.23 and 30.77% of PCL side chains attached to AXU at C3 and C2 positions, respectively. Although the attachment of PCL onto xylan led to the decreased thermal stability of xylan, the loss of unrecovered xylan fractions with low molecular weight because of the high solubility of xylan in DMSO/LiCl resulted in the increased thermal stability of the samples. This kind of xylan derivative has potential application in environmentally friendly and biodegradable materials considering the good biodegradability of xylan and PCL.

Carbohydrate composition of compost during composting and mycelium growth of Agaricus bisporus

Changes of plant cell wall carbohydrate structures occurring during the process to make suitable compost for growth of Agaricus bisporus are unknown. In this paper, composition and carbohydrate structures in compost samples collected during composting and mycelium growth were analyzed. Furthermore, different extracts of compost samples were prepared with water, 1M and 4M alkali and analyzed. At the beginning of composting, 34% and after 16 days of mycelium growth 27% of dry matter was carbohydrates. Carbohydrate composition analysis showed that mainly cellulose and poorly substituted xylan chains with similar amounts and ratios of xylan building blocks were present in all phases studied. Nevertheless, xylan solubility increased 20% over the period of mycelium growth indicating partial degradation of xylan backbone. Apparently, degradation of carbohydrates occurred over the process studied by both bacteria and fungi, mainly having an effect on xylan-chain length and solubility.

Evaluating pretreatment techniques for converting hazelnut husks to bioethanol

This study examined the suitability of husk waste for bioethanol production and compared pretreatment techniques with regard to their efficiencies. Results showed that 4% NaBH4 (90min) delignified the highest amount of lignin (49.1%) from the structure. The highest xylan solubility (77.9%) was observed when samples were treated with 4% NaOH for 90min. Pretreatment with NaOH and NaBH4, compared to H2O2 and H2SO4, resulted in selective delignification. The highest glucan to glucose conversion (74.4%) and the highest ethanol yield (52.6g/kg husks) were observed for samples treated with 2% NaOH for 90min.

Syntheses and characterization of xylan esters

A series of low-molecular weight and high-molecular weight xylan esters with different alkyl chain lengths (C2–C12) were synthesized by heterogeneous and homogeneous reactions, respectively. Structure elucidation of these xylan esters was obtained by NMR analysis. The solubility of xylan in CHCl3 improved after esterification. DSC results did not show a melting peak for all samples. However, WAXD diffractograms show the presence of diffraction peaks. The proposed structural model for xylan ester films is presented. TGA suggested that the thermal stability of xylan increased after esterification. Xylan esters with longer alkyl chains had higher decomposition temperatures. The mechanical properties of the xylan esters were dependent on the alkyl chain length. The tensile strength and elongation at break of these xylan esters ranged from 8 to 29 MPa and from 19 to 44%, respectively. Xylan esters in HFIP can be electrospun into nanofibers.

Ionic liquids from renewable biomaterials: synthesis, characterization and application in the pretreatment of biomass

A series of room temperature ionic liquids (ILs), in which cholinium acts as the cation and amino acids as the anions, were prepared via a simple and green chemical route, and characterized. Most of the ILs dissolved lignin efficiently and selectively (with solubilities of 140–220 mg of lignin per g of IL). The solubility of xylan in these ILs (which ranged from <1 to 85 mg g−1) depended on the nature of the anion, while cellulose was scarcely soluble (<5 mg g−1). In addition, enzymatic hydrolysis of microcrystalline cellulose and rice straw was enhanced significantly after pretreatment using the IL [Ch][Gly].

Synthesis and characterization of NaMt biocomposites with corn cob xylan in aqueous media

In this study synthesis and characterization of biopolymer/clay biocomposites was aimed using naturally occurring polysaccharide (xylan) as biopolymer and montmorillonite type clay (NaMt). Xylan was extracted from corn cobs via alkaline oxidative treatment. Maximum solubility of xylan was determined as 1% (w/v) in water at room temperature. Thus synthesis was realized following two routes; first NaMt concentration was kept constant at 2.0 × 10 −2 g/ml and xylan concentration was changed. Latter xylan concentration was kept constant at 1.0 × 10 −2 g/ml and NaMt concentration was changed. Natural xylan, NaMt and biocomposites were examined in terms of their spectral, electrokinetic, rheologic, morphologic and thermal properties. Results showed that lower amounts of xylan interacted with NaMt on the surface, however, when the xylan amount was increased also intercalation of NaMt has occurred. Biocomposites showed better thermal and rheologic behaviors with respect to the starting materials.

Effect of pretreatment severity on xylan solubility and enzymatic breakdown of the remaining cellulose from wheat straw

The effect of process conditions used for wheat straw pretreatments on the liquor- and residue-composition was studied. Hereto, the pretreatment conditions were expressed in a ‘combined severity R 0 ′ -factor’. The higher the combined severity factor ( R 0 ′ ) the more xylan was released from the wheat straw, but the more xylan decomposed and furfural formation occurred. The percentage of residual xylan present after pretreatment appeared to be a good indicator concerning cellulose degradability or bio-ethanol production. Namely, cellulose degradation by using commercial enzymes was higher at higher severities corresponding to a lower amount of residual xylan. The xylan release and degradation was studied in more detail by using HPSEC and MALDI-TOF mass spectrometry. The more severe the treatment the more (acetylated) xylose oligomers with a DP lower than nine were analysed. The presence of (acetylated) xylans with a DP of 9–25 increased slightly from low to medium severity. The quantification of the DP-distribution of the (acetylated) xylans released proved to be a good tool to predict cellulose degradability.

A Kinetic Study of Xylan Solubility and Degradation during Corncob Steaming

A process using a dilute acid pre-treatment followed by a dry-steaming to extract xylan from corncobs was studied with an emphasis on examining the kinetic characteristics of dry-steaming products (xylan, reducing sugar and furfural) with selected kinetic models. Corncobs with particle size of 4 · 75 mm were soaked in a 0·1% H2SO4 solution at 60 °C for 12 h before they were placed in an autoclave for a dry-steam processing at 125, 135, 145, and 155 °C. The yields of xylan, reducing sugar and furfural were fitted to a two-step first-order reaction model. The results suggested that the dilute acid pre-treatment followed by a dry-steaming process may have sensitised xylan to hydrolytic reactions and hence helped to lower the activation energy and increase the rate of xylan solubility. The yield of furfural during a 155 °C dry-steaming was 2·5–3·0 times higher than that at three other temperatures and hence was not recommended for use in xylan extraction.

Effect of Ozonation on Assembly of Xylans

Summary In this study the molecular structure of birch xylan was altered by ozonation. Longer ozonation times increased the cleavage of aromatic rings in the lignin residues attached to the xylan molecules, resulting in the formation of muconic acid derivatives and other carboxylic acid structures. Size exclusion chromatography showed a decreasing molar mass of xylan after ozonation. The ozonation improved xylan solubility as evidenced by the reduced amounts of aggregates in aqueous solution. Atomic force microscopy showed increases in the sizes of the aggregates. Furthermore, the ozonation resulted in a decreased ability of xylan to assemble into particle-like structures on cellulose surfaces. We therefore believe that there is a relationship between xylan aggregation in aqueous solution and the formation of xylan surface structures on cellulose.

Solubility and molecular weight of hemicelluloses from Alnus incana and Alnus glutinosa. Effect of tree age

The xylems of Alnus incana Moench. and Alnus glutinosa Gaertn. 8-15-year-old trees were subjected to comparative studies regarding the molecular weight (MW) of hemicelluloses. Extraction of hemicelluloses according to the sequence 1% NaOH-10% KOH-18% NaOH, followed by direct analysis of each extract using the SEC/UV method, was applied aiming at simultaneous quantitative and MW analysis. Both the tree age and alder species were found to affect the behaviour of hemicelluloses in alkaline solutions as well as their MW. Under equal extraction conditions, the solubility of xylan increased for A. incana and decreased for A. glutinosa with the tree age. For glucuronoxylan and glucomannan, a cyclic MW oscillation within a certain range throughout the tree growth was found. Both the sinusoid- and impulse-type of MW changes were suggested. The MW of arabinogalactan and xyloglucan decreased to a certain invariant value in the tree age period under investigation.