Microwave-induced synthesis of carboxymethyl hemicelluloses and their rheological properties

Renewable hemicellulose-based materials for value-added applications

The importance of renewable resources and environmentally friendly materials has grown globally in recent time. Hemicellulose is renewable lignocellulosic materials that have been the subject of substantial valorisation research. Due to its distinctive benefits, including its wide availability, low cost, renewability, biodegradability, simplicity of chemical modification, etc., it has attracted increasing interest in a number of value-added fields. In this review, a systematic summarizes of the structure, extraction method, and characterization technique for hemicellulose-based materials was carried out. Also, their most current developments in a variety of value-added adsorbents, biomedical, energy-related, 3D-printed materials, sensors, food packaging applications were discussed. Additionally, the most recent challenges and prospects of hemicellulose-based materials are emphasized and examined in-depth. It is anticipated that in the near future, persistent scientific efforts will enable the renewable hemicellulose-based products to achieve practical applications.

Valorization of Grain and Oil By-Products with Special Focus on Hemicellulose Modification

Hemicellulose is one of the most important natural polysaccharides in nature. Hemicellulose from different sources varies in chemical composition and structure, which in turn affects the modification effects and industrial applications. Grain and oil by-products (GOBPs) are important raw materials for hemicellulose. This article reviews the modification methods of hemicellulose in GOBPs. The effects of chemical and physical modification methods on the properties of GOBP hemicellulose biomaterials are evaluated. The potential applications of modified GOBP hemicellulose are discussed, including its use in film production, hydrogel formation, three-dimensional (3D) printing materials, and adsorbents for environmental remediation. The limitations and future recommendations are also proposed to provide theoretical foundations and technical support for the efficient utilization of these by-products.

Starch-fibers composites, a study of all-polysaccharide foams from microwave foaming to biodegradation

Sustainable composite foams based on rice starch and cellulosic long fibers were successfully fabricated using microwave irradiation. They were presented as a promising method to recycle some of the textile industry waste. A deep study of the processability and functionality of the composites revealed the performance improvement of starch with the addition of long cellulosic fibers, especially with 6 wt% of Arbocel®, in terms of foamability, water, and mechanical resistance features. Moreover, sodium bicarbonate, which acted as a blowing and pulping agent, led to a lower density and better fiber distribution that resulted in an improvement of the foams' functionalities. The range of the study is new in the domain of long fiber foam composites in terms of the foaming capability, and mechanical, thermal, and water resistance properties. Furthermore, all foams showed excellent biodegradability properties against a fungus commonly found in the environment; for example, values around 60 % weight loss after 33 days. Finally, the assessment of the CO2 emission during the process underlines the environmental benefits of the method employed.

A review on challenges and issues with carboxymethylation of natural gums: The widely used excipients for conventional and novel dosage forms

Diverse properties of natural gums have made them quite useful for various pharmaceutical applications. However, they suffer from various problems, including unregulated hydration rates, microbial degradation, and decline in viscosity during warehousing. Among various chemical procedures for modification of gums, carboxymethylation has been widely studied due to its simplicity and efficiency. Despite the availability of numerous research articles on natural gums and their uses, a comprehensive review on carboxymethylation of natural gums and their applications in the pharmaceutical and other biomedical fields is not published until now. This review outlines the classification of gums and their derivatization methods. Further, we have discussed various techniques of carboxymethylation, process of determination of degree of substitution, and functionalization pattern of substituted gums. Detailed information about the application of carboxymethyl gums as drug delivery carriers has been described. The article also gives a brief account on tissue engineering and cell delivery potential of carboxymethylated gums.

Defatted rice bran pretreated with deep eutectic solvents and sequential use as feedstock for subcritical water hydrolysis

Deffated rice bran has potential to processing into ethanol due to its lignocellulosic composition and agricultural productivity. The composition of the pretreated deffated rice bran with Deep Eutectic Solvent was investigated aiming the production of sugars and bioproducts using subcritical water hydrolysis. Changes in the deffated rice bran composition at different pretreatment times and mixtures of deep eutectic solvent were evaluated by the derivative of thermogravimetric analysis. The pretreated deffated rice bran presented an enrichment in the content of hemicelluloses (281.0%) and delignification (59.3 %). Under the same condition of subcritical water hydrolysis (230 °C/R-100) the yield of fermentable sugars increased 2.20 times in the same study time interval (20 min) when comparing pretreated and untreated deffated rice bran.

Effect of basil seed gum and κ-carrageenan on the rheological, textural, and structural properties of whipped cream

BACKGROUND

Basil seed gum (BSG) is a novel polysaccharide that has been found wide application in the food industry. It can be used in whipped cream due to its thickening and emulsifying properties. The effect of BSG and κ-carrageenan on the structure-rheology relationships of whipped cream was evaluated.

RESULTS

The viscosity of cream containing BSG was higher than that of carrageenan. Basil seed gum resulted in a strong capacity to improve the viscosity of the cream. Rheological results showed the low-frequency dependence of the elastic modulus was improved by BSG, which had a strong effect on the rigidity of the emulsion. The fracture strain of the creams containing BSG or κ-carrageenan was between the normal cream and acidified caseinate stabilized emulsion foam. It was found that the protein segments of BSG could be adsorbed at the oil-water interface, resulting in the formation of a pseudo-gel network, which creates a stronger molecular protein network in the whipped cream. Microstructure study revealed that whipped cream containing κ-carrageenan exhibited some flocculation, which could be caused by non-adsorbed polysaccharides or proteins. In contrast, cream containing BSGshowed more voids, which have considerably decreased by fat content and enhance the foam structure.

CONCLUSION

As a result, synergistic interactions between proteins and polysaccharides (BSG and κ-carrageenan) could promote the development of a cross-linked network. Indeed, due to its high levels of hydrophilicity, BSG absorbs water, acts as a thickening agent, and competes against caseinate at the interfaces and is incorporated into whipped cream to provide a more desirable physical structure for the product. © 2021 Society of Chemical Industry.

Polysaccharide extracted from Althaea officinalis L. root: New studies of structural, rheological and antioxidant properties

A water-soluble acidic polysaccharide (AOP-2) from Althaea officinalis L. root was isolated by water extraction and purified by ion exchange chromatography (Cellulose DEAE-52) and gel filtration (Sephadex G-200). The structure characteristics of AOP-2 was determined by gel permeation chromatography (GPC), high performance liquid chromatography (HPLC), fourier transform infrared (FT-IR), nuclear magnetic resonance (NMR) spectrum and gas chromatography-mass spectrometry (GC_MS). The results indicated that the AOP-2 was an acidic hetropolysaccharide with the molecular weight of 639.27 kDa. The AOP-2 composed of 51% galacturonic acid, 32.56% rhamnose, 12.73% glucose and 3.71% galactose. It could be found that the main backbone chain of AOP-2 consisted of →3)-α-D-GalpA-(1→, →3)-α-D-Rhap-(1→ and→3,4)-β-D-Galp-(1→ with branches of →4)-α-D-Rhap-(1→, →4)-α-D-Glcp-(1→ and α-D-Rhap-(1 → . Thermal analysis revealed that the AOP-2 had high thermal stability and according to the results obtained from XRD analysis, it had a semi-crystalline structure. The results of Steady-shear flow and dynamical viscoelasticity showed that AOP-2 solutions exhibited shear-thinning behavior with high viscosity and a weak gel-like behavior at concentrations above 1% in linear viscoelastic region. In addition, it showed relatively high antioxidant property.

A pH-sensitive semi-interpenetrating polymer network hydrogels constructed by konjac glucomannan and poly (γ-glutamic acid): Synthesis, characterization and swelling behavior

A novel pH-sensitive semi-interpenetrating polymer network (semi-IPN) hydrogel was prepared by using konjac glucomannan (KGM) and poly (γ-glutamic acid) (γ-PGA) with sodium trimetaphosphate (STMP) as the crosslinking agent. The structure of the semi-IPN hydrogels was characterized by FTIR spectra, thermogravimetric analysis (TGA), X-ray diffraction (XRD), rheological measurements, and scanning electron microscopy (SEM). The pH-sensitive effects were investigated by calculating the equilibrium swelling ratio (ESR) in buffer solutions (pH 2, 4, 6, and 8, respectively) at 37 °C. These results showed that the content of cross-linker and γ-PGA has a significant influence on the hydrogels' structure and swelling behavior. In vitro drug release behavior of semi-IPN hydrogels was investigated under simulated gastric and intestinal fluids using model drug Nicotinamide (NTM), and various models were applied to describe the drug release behaviors. The obtained results indicated that our synthesized semi-IPN hydrogel had the potential to be used as a suitable biomaterial carrier for functional components or drug delivery in the intestine.

Molecular modification, structural characterization, and biological activity of xylans

The differences in the source and structure of xylans make them have various biological activities. However, due to their inherent structural limitations, the various biological activities of xylans are far lower than those of commercial drugs. Currently, several types of molecular modification methods have been developed to address these limitations, and many derivatives with specific biological activity have been obtained. Further research on structural characteristics, structure-activity relationship and mechanism of action is of great significance for the development of xylan derivatives. Therefore, the major molecular modification methods of xylans are introduced in this paper, and the primary structure and conformation characteristics of xylans and their derivatives are summarized. In addition, the biological activity and structure-activity relationship of the modified xylans are also discussed.

Synthesis and Characterization of Hydrophobically Modified Xylans

Xylan is a major type of hemicellulose that has attracted a lot of research and development activities. It is often derivatized in order to improve its properties. In the literature, hydrophobic modification of polymers is often used to produce surfactant-like materials and associative thickeners. In this work, we have derivatized xylan with alkyl ketene dimer (AKD) and two types of alkenyl succinic anhydrides (ASAs). The xylan-AKD derivatives have been made at 90 °C, using dimethyl sulfoxide as solvent and 4-dimethylaminopyridine as promoter. Samples with degrees of substitution (DS) up to 0.006 have been produced. The xylan-ASA derivatives have been synthesized at 120 °C in dimethyl sulfoxide with DS up to 0.105-0.135. The structures of these products have been confirmed with NMR and FT-IR. These xylan derivatives increase the structural diversity of xylan and provide additional options for people seeking to use hydrophobically modified polysaccharides in their applications.

Plant celluloses, hemicelluloses, lignins, and volatile oils for the synthesis of nanoparticles and nanostructured materials

A huge variety of plants are harvested worldwide and their different constituents can be converted into a broad range of bionanomaterials. In parallel, much research effort in materials science and engineering is focused on the formation of nanoparticles and nanostructured materials originating from agricultural residues. Cellulose (40-50%), hemicellulose (20-40%), and lignin (20-30%) represent major plant ingredients and many techniques have been described that separate the main plant components for the synthesis of nanocelluloses, nano-hemicelluloses, and nanolignins with divergent and controllable properties. The minor components, such as essential oils, could also be used to produce non-toxic metal and metal oxide nanoparticles with high bioavailability, biocompatibility, and/or bioactivity. This review describes the chemical structure, the physical and chemical properties of plant cell constituents, different techniques for the synthesis of nanocelluloses, nanohemicelluloses, and nanolignins from various lignocellulose sources and agricultural residues, and the extraction of volatile oils from plants as well as their use in metal and metal oxide nanoparticle production and emulsion preparation. Furthermore, details about the formation of activated carbon nanomaterials by thermal treatment of lignocellulose materials, a few examples of mineral extraction from agriculture waste for nanoparticle fabrication, and the emerging applications of plant-based nanomaterials in different fields, such as biotechnology and medicine, environment protection, environmental remediation, or energy production and storage, are also included. This review also briefly discusses the recent developments and challenges of obtaining nanomaterials from plant residues, and the issues surrounding toxicity and regulation.

Preparation and characterization of pH-responsive microgel using arabinoxylan from wheat bran for BSA delivery

Wheat bran arabinoxylan (AX) discard from wheat production was utilized to form pH-responsive microgels. AX was modified by carboxymethylation, and the carboxymethylated arabinoxylans (CMAX) were characterized by FT-IR, NMR, gel permeation chromatography (GPC), and rheological analysis. The CMAX microgel was cross-linked by Fe³⁺ using an inverse emulsification polymerization. The morphology, particle size, pH sensitivity, and mechanism of cross-linking between COO^- and Fe³⁺ of the CMAX microgel was investigated. The CMAX microgel was used to be an oral protein drug carrier. The CMAX microgel particles exhibited a stable spherical structure. FT-IR spectral analysis of the CMAX microgel indicated that the microgel was crosslinked by bridging Fe³⁺ and COO^- with unidentate binding. The CMAX microgel exhibited good pH sensitivity and high stability in acid condition. Additionally, BSA was used as the embedding protein, and the controlled release effect of CMAX microgel was explored in gastrointestinal tract simulation.

Valorization of industrial xylan-rich hemicelluloses into water-soluble derivatives by in-situ acetylation in EmimAc ionic liquid

In this study, aimed at valorization of industrial xylan-rich hemicelluloses (a by-product of dissolving pulp process), water-soluble hemicelluloses were fabricated with mild acetylation in 1-ethyl-3-methylimidazolium acetate ionic liquid (EmimAc) and dichloroacetyl chloride (Cl₂AcCl) system by a facile and novel method. The structure of the acetylated hemicelluloses was characterized by FT-IR and NMR spectra. The resultant modified products could fully dissolve in water with the degree of substitution (DS) valued between 0.17 and 0.37. Structural characterization indicated that the modified hemicelluloses were chiefly composed of the (1 → 4)-linked β-D-Xylp backbone with hydroxyl or -COCH₃ linked to O-2 and O-3 of the Xylp units. Moreover, the mild acetylation was achieved by one-pot method, in which the hemicelluloses reacted with mixed anhydride produced between EmimAc and Cl₂AcCl rather than Cl₂AcCl. Rheological behavior measurements revealed that acetylated hemicelluloses solutions showed shear-thinning behavior and indicated lower viscosity compared with those of the referenced hemicelluloses. The excellent water-solubility of industrial hemicelluloses would widen its application field and be easier for its conversion into desired chemicals.

Rheological properties of soy protein isolate – carboxymethyl flaxseed gum mixed dispersions under large amplitude oscillatory shear

Carboxymethyl flaxseed gum (CMFG) is developed in our laboratory by modifying flaxseed gun through carboxymethylation. The aim of this study is to reveal the rheological properties of soy protein isolate – carboxymethyl flaxseed gum (SPI-CMFG) mixed dispersion in realistic processing conditions by conducting large amplitude oscillatory shear (LAOS) test, with consideration of concentration and degree of substitution (DS) of CMFG. Results showed that increasing CMFG concentration significantly increased storage moduli (Gʹ), loss moduli (Gʺ), and the apparent viscosity of all SPI-CMFG mixed dispersions. LAOS test illustrated that the dispersions experienced a transition from LAOS type IV to type III after increasing the concentration of CMFG, while the behavior converted from LAOS type I to type III by increasing DS. Fourier transform rheology (FTR) exhibited that increasing the concentration or DS of CMFG both induced a conversion from “soft sphere” to “hard sphere” behavior. The strain-stiffening ratio S and the shear-thickening ratio T demonstrated, that all SPI-CMFG dispersions experienced a similar conversion from strain stiffening to strain softening, and from shear thinning to shear thickening behaviors by increasing the concentration of CMFG. Nevertheless, the mixed dispersions presented shear thickening behaviors when DS was no more than 0.520 in the whole range of strain, while a conversion from shear thinning to shear thickening behavior occurred, when DS reached at 0.755 and 0.973.

Preparation of a Novel Lignin Nanosphere Adsorbent for Enhancing Adsorption of Lead

Carboxymethyl lignin nanospheres (CLNPs) were synthesized by a two-step method using microwave irradiation and antisolvent. The morphology and structure of CLNPs were characterized by ³¹P-NMR, FTIR, and SEM, and the results showed that they had an average diameter of 73.9 nm, a surface area of 8.63 m² or 3.2 times larger than the original lignin, and abundant carboxyl functional groups of 1.8 mmol/g. The influence of dosage, pH, contact time, and concentration on the adsorption of metal ions onto CLNPs were analyzed, and the maximum adsorption capacity of CLNPs for Pb(II) was found to be 333.26 mg/g, which is significantly higher than other lignin-based adsorbents and conventional adsorbents. Adsorption kinetics and isotherms indicated that the adsorption of lead ions in water onto CLNPs followed the pseudo-second-order model based on monolayer chemisorption mechanism. The main chemical interaction between CLNPs and lead ions was chelation. CLNPs also showed an excellent recycling performance, with only 27.0% adsorption capacity loss after 10 consecutive adsorption–desorption cycles.

Microstructure and chemorheological behavior of whipped cream as affected by rice bran protein addition

The effect of rice bran protein (RBP) isolate addition on the rheological and structural properties of commercial whipped cream with 25% and 35% fat was investigated. Results showed that increasing the fat content from 25% to 35% leads to an increase in the elastic modulus. Furthermore, by increasing the amount of RBP from 1% to 3% in both creams, significant increase occurred in the complex modulus. As the fat content increased from 25% to 35%, the slope of flow behavior was increased, which revealed more thinning behavior and pseudoplasticity index of cream. The cream containing 35% fat and 3% RBP had also shown the low index (n = 0.298) which confirmed the firmer structure of the cream. The maximum consistency index (k) obtained was 9.41 for the cream with 35% fat and 3% RBP, which approved its strong foam structure. In general, according to our results it is obvious that whipped cream with the highest amount of fat and the lowest value of protein can lead to maximum stability of the whipping cream. Among the samples, the lowest stiffness was observed in cream of 35% fat, containing 3% rice bran protein. However, cream containing 35% fat and 1% RBP had convenient overrun and good stability. The microstructural results showed that the cream structure has relatively large globular aggregates in network and develops large pores, which permit to retain sufficient water/air. By increasing the fat content of cream from 25% to 35%, the voids and spaces in the cream were significantly decreased and the pores become less which improve the foam structure. Therefore, it can be concluded the cream with more fat has the more overrun and stability. In general, it is possible to improve the foam structure of cream by substituting fat by RBP.

Xylan-Based Hydrogels as a Potential Carrier for Drug Delivery: Effect of Pore-Forming Agents

Pore-forming agents have a significant influence on the pore structure of hydrogels. In this study, a porogenic technique was employed to investigate the preparation of macroporous hydrogels which were synthesized by radical copolymerization of carboxymethyl xylan with acrylamide and N-isopropylacrylamide under the function of a cross-linking agent. Six kinds of pore-forming agents were used: polyvinylpyrrolidone K30, polyethylene glycol 2000, carbamide, NaCl, CaCO₃, and NaHCO₃. The application of these hydrogels is also discussed. The results show that pore-forming agents had an important impact on the pore structure of the hydrogels and consequently affected properties of the hydrogels such as swelling ratio and mechanical strength, while little effect was noted on the thermal property of the hydrogels. 5-Fluorouracil was used as a model drug to study the drug release of the as-prepared hydrogels, and it was found that the drug release was substantially improved after using the NaHCO₃ pore-forming agent: a cumulative release rate of up to 71.05% was achieved.

Synthesis and Characterization of Periodate-Oxidized Polysaccharides: Dialdehyde Xylan (DAX)

The cleavage of the C2-C3 bond in the building units of 1 → 4-linked polysaccharides by periodate formally results in two aldehyde units, which are present in several masked forms. The structural elucidation of such polysaccharide dialdehydes remains a big challenge. Since polysaccharide derivatives are increasingly applied in materials technology, unveiling the exact structure is of utmost importance. To address this issue for xylan, dialdehyde xylan (DAX, oxidation degree of 91.5%) has been synthesized as water-soluble polymer. The ATR-FTIR spectrum of DAX showed free aldehyde to be absent and exhibited a characteristic absorption at 858 cm(-1) related to hemiacetal groups. By a combination of 1D and 2D NMR techniques, it was confirmed that oxidized xylan is present as poly(2,6-dihydroxy-3-methoxy-5-methyl-3,5-diyl-1,4-dioxane). Based on GPC analysis, the DAX polymer shows a slightly lower molar mass (6.6 kDa) compared to the starting material (7.7 kDa) right after oxidation, and degraded further after one month of storage in 0.1 M NaCl solution (4.3 kDa). The oxidized xylan demonstrated lower thermal stability upon TGA analysis and a greater amount of residual char (20.6%) compared to the unmodified xylan (13.7%).

Graphene Oxide/Polyacrylamide/Aluminum Ion Cross-Linked Carboxymethyl Hemicellulose Nanocomposite Hydrogels with Very Tough and Elastic Properties

Development of high-strength hydrogels has recently attracted ever-increasing attention. In this work, a new design strategy has been proposed to prepare graphene oxide (GO)/polyacrylamide (PAM)/aluminum ion (Al(3+) )-cross-linked carboxymethyl hemicellulose (Al-CMH) nanocomposite hydrogels with very tough and elastic properties. GO/PAM/Al-CMH hydrogels were synthesized by introducing graphene oxide (GO) into PAM/CMH hydrogel, followed by ionic cross-linking of Al(3+) . The nanocomposite hydrogels were characterized by means of FTIR, X-ray diffraction (XRD), and scanning electron microscopy/energy-dispersive X-ray analysis (SEM-EDX) along with their swelling and mechanical properties. The maximum compressive strength and the Young's modulus of GO3.5 /PAM/Al-CMH0.45 hydrogel achieved values of up to 1.12 and 13.27 MPa, increased by approximately 6488 and 18330 % relative to the PAM hydrogel (0.017 and 0.072 MPa). The as-prepared GO/PAM/Al-CMH nanocomposite hydrogels possess high strength and great elasticity giving them potential in bioengineering and drug-delivery system applications.

Green synthesis of palladium nanoparticles via branched polymers: a bio-based nanocomposite for C–C coupling reactions

Renewable and sustainable CMH was the natural ligand for CMH–Pd(0) nanocomposite which was as an efficient and recyclable catalyst for Heck reaction.

Homogeneous acylation of xylan with 3,5-dinitrobenzoyl in ionic liquid and the adsorption property

A new xylan ester (xylan 3,5-dinitrobenzoate) as a creatinine adsorbent was prepared by the homogeneous acylation of xylan with 3,5-dinitrobenzoyl chloride in 1-butul-3-methylimidazolium chloride ionic liquid. The influences of reaction conditions on the degree of substitution values of xylan esters were discussed. Results indicated that xylan esters with the degree of substitution range from 1.34 to 1.77 were obtained under the given conditions. The FTIR and (13)C NMR spectroscopies provided the evidence of grafting 3,5-dinitrobenzoyl groups onto the backbone of xylan. Moreover, the adsorption properties of the xylan ester for creatinine were also investigated. Isotherm studies showed that the sorption capacities for creatinine were 2.45, 2.08 and 1.86 mg/g for 23, 30 and 37 °C, respectively. Thermodynamic studies performed indicated the sorption process mainly was controlled by the chemical adsorption. Therefore, xylan 3,5-dinitrobenzoate displayed the promising application in the treatment of chronic renal failure by the creatinine adsorption as the new oral adsorbent.

Multiresponsive hydrogels based on xylan-type hemicelluloses and photoisomerized azobenzene copolymer as drug delivery carrier

Stimulus-responsive hydrogels, which can undergo significant physicochemical changes in response to various physical or chemical stimuli, have drawn wide attention in many fields. In this study, novel photoresponsive hydrogels prepared by free radical copolymerization of xylan-type hemicellulose methacrylate with 4-[(4-acryloyloxyphenyl)azo]benzoic acid (AOPAB) were investigated, which showed multiresponsive behaviors to pH, water/ethanol alternating solutions, and light. The swelling ratios of the prepared hydrogels in distilled water decreased from 9.8 to 2.2 g/g with AOPAB content increase from 2% to 16%. The hydrogel displayed rapid swelling and deswelling performance in water and ethanol alternating solutions. Additionally, under UV irradiation the trans-conformation of azobenzene in the hydrogel would generally convert into the cis-conformation and resulted in the hydrophilic/hydrophobic balance variation of the hydrogel. Therefore, the hydrogel loaded with vitamin B12 (VB12) showed a higher drug cumulative release rate under UV irradiation than that without UV irradiation.

Comparative study of the pyrolysis of lignocellulose and its major components: characterization and overall distribution of their biochars and volatiles

In order to investigate the pyrolysis differences among lignocellulose and its major components, the biochars and volatiles of lignocellulose (bamboo), lignin, hemicellulose and holocellulose (from bamboo), and cellulose (from cotton linter) were studied using elemental analysis, FTIR, XRD, SEM, Py-GC/MS and TGA-FTIR. Result showed that the biochar yield of lignin (48.8%) was much higher than those of hemicellulose (21.1%), cellulose (8.3%), holocellulose (20.4%) and bamboo (15.1%), while no obvious elemental difference among these biochars was found. Results from Py-GC/MS indicated that carbonyl compounds, ethers and alcohols were the major volatiles of polysaccharide component pyrolysis, while aromatic compounds were the major volatiles of lignin pyrolysis. The pyrolysis of polysaccharide component mainly occurred at 200-400°C, while the pyrolysis of lignin happened at 300-700°C.

Novel hydrophobic hemicelluloses: synthesis and characteristic

Novel hydrophobic hemicelluloses possessing hydrophobic groups were prepared by the benzylation of wheat straw hemicelluloses with benzyl chloride under the presence of catalyst in an ethanol/water system. In particular, the progress of the benzylation reaction was studied as a function of the volume ratio of ethanol/water from 4:1 to 6:4, the molar ratio of NaOH/anhydroxylose unit in hemicelluloses from 0.6:1 to 1.5:1, the molar ratio of benzyl chloride/anhydroxylose unit in hemicelluloses from 0.5:1 to 2.0:1, reaction temperature 50-80 °C, and reaction time 4-20 h Benzylated hemicelluloses with the low degree of substitution from 0.09 to 0.35 were obtained depending on the experimental conditions. The incorporation of benzyl groups into the backbone of hemicelluloses was confirmed by FT-IR and (13)C NMR spectroscopies. The thermal stability increased after the modification of hemicelluloses due to the introduction of benzyl groups. The introduction of benzyl groups endows hemicelluloses with the hydrophobicity, which could be potentially applied in plastic industries.

Synthesis and characterization of amphoteric xylan-type hemicelluloses by microwave irradiation

In this study, a novel amphoteric macromolecule was synthesized by sequential incorporation of carboxymethyl and quaternary ammonium groups into the backbone of xylan-type hemicelluloses under microwave irradiation. The reaction parameters such as the molar ratio of reagent (NaOH or 3-epoxypropyltrimethylammonium chloride)/anhydroxylose unit in hemicelluloses, the temperature, and the reaction time were investigated to optimize the reaction condition. The maximum degrees of substitution (DS) of carboxymethyl and quaternary ammonium groups under the optimum reaction condition were 0.90 and 0.52, respectively, exhibiting a higher efficiency as compared to the conventional heating method. Moreover, the thermal stability and weight-average molecular weight of amphoteric hemicellulosic derivatives decreased as compared to the native hemicelluloses. The viscosity, elastic modulus, and loss modulus of the amphoteric biomacromolecules increased with the increasing DS of quaternary ammonium groups in aqueous solution due to stronger electrostatic attraction. This study provides an efficient and rapid method to prepare amphoteric biomacromolecules.

Functional Modification of Xylan-Rich Hemicelluloses in Ionic Liquid

Xylan-rich Hemicelluloses (XH) isolated from wheat straw were converted to functional biopolymers by modification using succinic anhydride (SA) as reactant without catalyst in 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) ionic liquid. The reaction was performed under various conditions such as different temperatures, different times, and the different amounts of SA, and the effect of reaction factors on the degree substitution (DS) of products were discussed. The product had the maximum DS of 1.80. The structure of modified hemicellulosic derivatives (MD) was actually confirmed by13C NMR spectroscopy. The thermal behavior of MD was monitored by means of thermogravimetry (TG) and differential thermal analysis (DTA), and the thermal stability of MD was lower than XH.