Optimizing hemicelluloses pre-extraction in eucalyptus kraft pulping:A pathway towards enhancing pulp mill biorefineries

A critical pathway towards enhancing pulp mill biorefineries is to integrate the extraction and utilization of hemicelluloses into the pulping processes.Hence,an industrial pre-extraction strategy for hemicelluloses targeting eucalyptus kraft pulping process was developed.Alkaline solution or pulping white liquor was used to pre-extract hemicelluloses before the actual pulping process.The response surface methodology(RSM)technique was applied to investigate the most suitable conditions to maximize the yield of these hemicelluloses while simultaneously minimizing the damage to pulp yields and properties.Temperature(105 to 155℃),alkali concentration(3%to 8%),sulfidity(20%to 30%)and retention time(19 to 221 min)were combined to evaluate their effects on hemicellulose yields and chemical structures.The optimal pre-extraction conditions identified in this work(5.75%NaOH concentration,25%sulfidity at 135℃for 60 min)successfully allowed recovering 4.8%of hemicelluloses(based on the wood dry mass)and limited damages to pulp yields and properties.The cellulose content in pulp can even be increased by about 10%.Hemicellulose emulsification properties were also evaluated,which were comparable to synthetic emulsifiers.This study provides an industrial pathway to effectively separate and utilize wood hemicelluloses from the pulping process,which has the potential to improve the economy and material utilization of pulp and paper mills.

Efficient hydrolysis of hemicellulose to furfural by novel superacid SO_4H-functionalized ionic liquids

Novel superacid SO_4H-functionalized ionic liquids(SFILs) were designed and prepared in this work. The catalytic activities of SFILs were evaluated in xylan hydrolysis and xylose dehydration to produce furfural. Combined with the results of acid strength of SFILs characterized by solid-state ^(31)P MAS NMR, it was found that the catalytic performance of SFILs was positively correlated to their acid strength. The superacid SFIL [Ch-SO_4H][CF_3SO_3] displayed the best catalytic performance with more than 80% yield of furfural, and it was also obviously superior to usual SO_3H-functionalized acidic ILs, mineral liquid acids, and acidic resin Amberlyst-15 catalysts in catalytic activity under optimized conditions. In addition, the superacid SFIL [Ch-SO_4H][CF_3SO_3] could be easily separated from reaction system and reused at least five times without obvious decrease.

Isolation of Hemicellulose from Wood Chips via Extraction with Kraft Green Liquor

The present paper covers the extraction of hemicelluloses from woods, i.e., Eucalyptus Globulus, white fir and Douglas fir via green liquor pretreatment and alkali post-treatment with sodium hydroxide. The effects of such extraction conditions as extraction time, temperature on the yields of hemicellulose and the degree of deliginification were investigated. Sugar analyses using Dionex indicate that xylose, glucose and mannose are the main sugar types present in the hemicellulose from Eucalyptus. Other sugar components such as arabinose and galactose were also found in Dogulas fir hemicellulose. The highest yield of hemicellulose was 8.4% for Eucalyptus extracted with green liquor at 130 ℃ for 3.5 h. Further sodium hydroxide extraction for 5 h gave a hemicellulose yield of about 20%. The use of green liquor for the extraction of wood hemicellulose is believed to be the first attempt.

Characterization of Hemicelluloses Extracted from Populus tomentosa Carr. by the Hydrothermal Method with Ethanol

The aim of this study was to investigate the hemicelluloses extracted from Populus tomentosa Carr.by the hydrothermal method with ethanol.The influence of ethanol concentration on the hemicellulosic fractions was systematically studied.The chemical compositions and structural features of the hemicellulosic fractions were investigated by a combination of sugar analysis,gel-permeation chromatography,Fourier transform infrared spectroscopy,and one-dimensional proton and carbon-13 nuclear magnetic resonance,and two-dimensional heteronuclear single quantum coherence spectroscopy.Neutral sugar analysis of the hemicellulosic fractions revealed that a higher ethanol concentration(45%~80%) favored the isolation of hemicelluloses with more side chains and lower glucose contents.The molecular weights of these polysaccharides ranged between 2842 g/mol and 5101 g/mol.The results of this study indicate that the hydrothermal ethanol process provides a new pretreatment strategy for the isolation and extraction of biomass.

Comparative Study of Water-soluble and Alkali-soluble Hemicelluloses Extracted by Hydrothermal Pretreatment

The purpose of this study was to explore the differences of the hemicelluloses extracted by hydrothermal pretreatment using water and alkaline solutions(Na OH or KOH). The physicochemical properties and structural characteristics of two water-soluble and four alkali-soluble hemicelluloses extracted from the triploid of Populus tomentosa Carr. through the hydrothermal pretreatment were comparatively studied. It was observed that the alkalis(Na OH and KOH) were more effective than distilled water as extractants. Sugar analysis showed that xylose(66.83%~86.49%) was the major constituent, followed by glucose(6.83%~18.49%). Mannose(1.40%~8.42%), galactose(2.17%~4.05%), and arabinose(0.21%~2.26%) were also detected in the hemicellulosic fractions. The results of gelpermeation chromatography(GPC) indicated that the hemicelluloses extracted using the alkaline solutions had relatively higher molecular weights than those solubilized in distilled water. Further, based on spectroscopic ~1Hnuclear magnetic resonance(~1H-NMR) and two-dimensional heteronuclear singular quantum correlation(2D-HSQC) analyses, it was confirmed that the hemicellulosic fractions had a major structure of(1→4)-b-D-xylan and a minor structure of(1→4)-a-D-glucan with small amounts of substituted sugars and glucuronic acid attached.

Hemicellulose in corn straw:Extracted from alkali solution and produced5-hydroxymethyl furfural in HCOOH/HCOONa buffer solution

Hemicellulose in corn straw is a group of complex heteropolysaccharides which are composed of different sugar units, including mannans, xylans, arabinans and galactans. This study developed a simple and practical process for production of 5-hydroxymethyl furfural(HMF) using hemicellulose that was extracted from corn straw. In the hemicellulose degradation process HCOOH/HCOONa was used as buffer solution, and the optimum conditions for maximum HMF yield were explored. Various extraction conditions including NaOH concentration, reaction time,temperature, solid-to-liquid ratio and precipitant were tested for hemicellulose obtaining, giving the optimum condition of 55 °C, 4 h, solid-to-liquid ratio of 1:10, 1.5 mol·L^(-1) NaOH solution and ethanol as precipitant with the yield of 34.16%. Dehydration of hemicellulose under HCOOH/HCOONa buffer solution process, using solution medium of pH = 0.8 hydrolyzed hemicellulose in corn straw at 190 °C after 190 min and 82% of HMF yield was achieved.

Extraction of Hemicellulose from Acacia Wood via Autohydrolysis and Ethanol Precipitation

Isolation and utilization of hemicellulose are important processes in the pulp mill-based biorefinery. Considering the potential end use of the hemicellulose,this study investigated the concentration of monomeric and oligomeric sugars in the hydrolysate derived from autohydrolysis of acacia wood and the obtainment of these sugars via ethanol precipitation. The rate of generation of monomers and oligomers increased dramatically with an increase of the temperature from 160℃ to 180℃. The maximum content of oligomers and total sugars was achieved under conditions of 180℃ and 10 min,170℃ and 85 min,respectively. Interestingly,the maximum yield of hemicellulose via ethanol precipitation was achieved in a much shorter time,compared with the maximum yield of oligomer from the hydrolysate by autohydrolysis. A 6. 66 g / L quantity of hemicellulose was obtained by intensifying the conditions of ethanol precipitation. The hemicellulose characteristics were analyzed by Fourier transform infrared,nuclear magnetic resonance,and ultraviolet spectroscopy,and the molecular weight was determined by gel permeation chromatography and thermal analysis.

Xylo-Oligosaccharide Preparation through Enzyme Hydrolysis of Hemicelluloses Isolated from Press Lye

The emerging food additive, xylo-oligosaccharide(XOSs), was prepared through enzymatic hydrolysis of hemicelluloses isolated from press lye. Two of the three experimental enzyme preparations presented favourable effects, while the other one consisting of the nominal enzyme preparations with high enzyme activity was found to have poor catalytic effects. The conversion of xylan exceeded 40% and the selectivity for XOSs reached 90% when the temperature, hemicellulose concentration, dosage of enzymes, and hydrolysis time were 40?C, 100 g/L, 1 ku/g, and 4 h, respectively. Xylo-oligosaccharide preparation through enzymatic hydrolysis of hemicelluloses isolated from press lye was proved to be a feasible process to utilize the by-product of the lye regeneration, which will substantially improve the economy of the lye regeneration and recycling.

Xylo-oligosaccharides preparation through acid hydrolysis of hemicelluloses isolated from press-lye

The preparation of xylo-oligosaccharides(XOSs)through hydrolysis of hemicelluloses was studied.The hemicelluloses were isolated from the press lye discharged in the production of viscose,which contained about 30%xylan.Then,a factorial experimental design was applied to compare the influences of several factors including the concentrations of sulphuric acid and hemicelluloses,the duration and temperature of the hydrolysis,on the conversion of xylan,and the selectivity for the product–XOSs.The results showed that the hydrolysis duration affects the yield of XOSs to the greatest extent.It is difficult to obtain a high yield of XOSs with sulphuric acid as the hydrolysis catalyst.

Hemicellulose-Based Hydrogels Present Status and Application Prospects: A Brief Review

Hemicellulose is one of the most abundant natural resources, which extensively exist in the pant tissues as the compositions of the cell wall filling between lignin and cellulose. In this review, the hemicellulose based hydrogels was illustrated in details including the hemicellulose derivatives (such as precursor of hemicellulose based hydrogel), hydrogels fabrication methods, origin of hemicellulose, composite hydrogels, and so on. In addition, the authors as well overviewed the new methods for fabrication of hemicellulose based hydrogels and special functional hemicellulose based hydrogels.

Extraction,Purification,and Applications of Hemicellulose

In addition to cellulose and lignin,hemicellulose is an important biomass material.Recently,hemicellulose and its derivatives and materials have attracted increasing attention owing to their unique structures,improved properties,and promising application potential,and many reports on the extraction,isolation,and modification of hemicellulose are currently available.We summarized the recent developments of hemicellulose and its derivatives and materials by focusing on the extraction,purification,and modification of hemicellulose.The synthesis of hemicellulose-based derivatives and materials was also reviewed.Various methods of extracting,isolating,and modifying hemicellulose were discussed.Remaining challenges related to hemicellulose extraction,purification,and application were mentioned,and directions for further research on hemicellulose were proposed.

Characteristics of Carboxymethyl Hemicellulose(CMX)and Its Strengthening Mechanism

In this study,three kinds of rough-wrought hemicelluloses(RHCs)were obtained via alkali extraction on different raw materials.One was untreated Phyllostachys edulis powder;the second was obtained via benzyl alcohol extraction of Phyllostachys edulis powder;and the third was holocellulose of Phyllostachys edulis powder.Carboxymethyl hemicelluloses(CMXs)were prepared by the alkalization and etherification of RHCs and were used to enhance the tensile strength of household paper.The results demonstrated a synergistic effect between CMX and polyamide epichlorohydrin resin(PAE),and the addition of small amount of CMX(0.35 kg/t pulp)can significantly improve the dry and wet tensile indices of paper.Study results of CMX strengthening mechanism revealed that the addition of CMX can improve the retention of PAE,especially the fine fiber,due to the adsorption of charges.The use of CMX in paper not only saves production costs but also reduces the proportion of long fiber,which is beneficial to the closed circulation and treatment of white water.

Preparation and Characterization of Hydrophobic Bagasse Hemicellulosebased Films

To improve the hydrophobicity of bagasse hemicellulose-based films,glutaraldehyde was applied when preparing films of original and cationic bagasse hemicellulose with the addition of polyvinyl alcohol and sorbitol.The results showed that the cationic modification could increase the hydrophobicity of the hemicellulose-based film,and the hydrophobicity of hemicellulose-based films crosslinked with glutaraldehyde also increased.However,cationic modification of hemicellulose decreased the stress of the hemicellulose-based film.While crosslinking with glutaraldehyde increased the stress of both the original and cationic hemicellulose-based films.Macrophotography indicated that the film formability of the original hemicellulose was better than that of cationic hemicellulose.Through SEM observation,the degree of bonding of different components of the films was found to be increased due to crosslinking with glutaraldehyde.The crosslinking reaction between glutaraldehyde and hemicellulose was further confirmed by FT-IR spectroscopy.

Green and Effective Ammonium Carbonate-assisted Process for Drying Hemicellulose Obtained through Alkali Extraction of Bleached Bamboo Kraft Pulp

Hemicellulose has a wide range of applications,including that as an emulsifier for the food industry and raw material for the synthesis of bioethanol/biochemicals and biodegradable films.Hemicellulose is usually present as a spent liquor,such as the prehydrolysis liquor of the prehydrolysis kraft dissolving pulp production process and the alkali extraction liquor of the cold caustic extraction of pulp fibers.Due to its dilute nature,hemicellulose needs to be dried for practical utilization,and this is challenging.In this study,cellulose and hemicellulose in a bleached bamboo kraft pulp were separated using an alkali extraction process.Hemicellulose obtained from the extraction liquor was dried by an ammonium carbonate-assisted drying process.The effects of drying time and drying temperature were determined.Structure of the hemicellulose obtained by the ammonium carbonate-assisted drying process was similar to that of original hemicellulose,as revealed by detailed Fourier transform infrared and X-ray diffraction analyses.The novel drying method was more energy efficient and required a shorter drying time than the conventional freeze drying method,and the excellent solubility in alkaline solutions favored the chemical modification of hemicellulose.The dried hemicellulose can be used as a renewable raw material for the preparation of hydrogels and other substances such as bioethanol/biochemicals and biodegradable films.

Hemicellulose-Based Polymers Processing and Application

Hemicellulose is the second most abundant biomass in the world. Because of its unique chemical structure, hemicellulose has attracted more and more research and industry application under the background of fossil resource shortage and drawbacks. Hemicellulose is tended to be modified with esterification, etherification, cross-linkage and so on. These reactions change hemicellulose properties, so that it could be applied in many fields such as medical field, films, hydrogels, conductive polymers. Herein, we reviewed structure, isolation, reaction and applications of hemicellulose. Especially the useful pathways to change the hydrophilic character of hemicelluloses to hydrophobic are reviewed and several applications of these materials are discussed.

Binding Ability of Corn Cobs Hemicellulose toward Cadmium

Non-Starch Polysaccahride (NSP) is an agricultural byproduct containing of cellulose, hemicelluloses, and lignin. Hemicellulose has a hydroxyl functional group and carboxylic function on the monomer hemicellulose used as a binding ability for cadmium ion and hence as a pharmaceutical active ingredient to prevent cadmium toxicity. The purpose of this study is to isolate and evaluate hemicelluloses from corn cobs as a binding ability toward cadmium ion. The study is conducted by isolating the corn cobs in such way using 0.2 M NaOH, characterization of hemicellulose from corn cobs produced by Infra Red Spectrofotometry. Binding ability of corn cobs hemicellulose (CCH) was done in 3 ways. The first, it was by titrimetric with cadmium 3 mg/cm3 as a titrant and indicator of 0.05 N NaOH. The second, it was by in vitro test at pH 2 as a comparison to use pectin. The third, the in vivo test was conducted in 3 variations of treatment covering CCH 10 mg, 100 mcg of cadmium for 10 weeks. Assay of cadmium was conducted using atomic absorption spectrophotometry with flame at a wavelength of 228.8 nm. The research result showed that the highest yield of hemicellulose (12.04%) was obtained from delignication with 0.03 M NaOH in 60% ethanol and 3% H2O2, hemicellulose isolation with 500 cm3 of 0.2 M NaOH, and precipitation with 1:4 ratio of 10% acetic acid in 95% ethanol. Characteristics of CCH on infrared vibration methods provide vibrational hemicellulose in the region of 1820-1600 cm-1. It meant that the functional group carbonyl was present, and the vibration widened near 3400-2400 cm-1. It indicated that there was the functional group vibration region of hydroxyl. It also meant that there was carboxylic group and finger print at 1500-500 cm-1. Test results of the titrimetric holding ability showed that CCH was binding 100 mg of cadmium (46.17 ± 0.9256) mg or 46.17%. Binding ability test results at pH 2 showed that 300 mg of CCH yield was binding 30 mg cadmium of (26.68 ± 0.1490) mg or 88.93%. The results of in vivo tests showed that cadmium levels decreased by 95.05%. Based on the exposure, it can be concluded that the CCH isolation yields of 12.04% and can reduce cadmium levels in the blood. It means that the CCH can be used as a chelating agent of cadmium ions by in vitro and in vivo.

Microwave-Assisted Hydrolysis of Hemicellulose over Sulfonated Catalysts

Sulfonated catalysts based on zirconia (SO3H-ZrO2), silica (SO3H-SBA-15) and zeolite (SO3H-ZSM-5) were studied in the catalytic hydrolysis reaction of hemicellulose in a microwave reactor. The prepared catalysts were characterized by various techniques (XRD, N2 physisorption at 77 K, SEM, TEM and NH3-TPD). The obtained results reveal that despite the differences in their structural and textural properties, the ZrO2, Al-SBA-15 and H-ZSM-5 supports show similar conversions. Doping supports with sulfonate species created hydrogen bonds between SO3H groups and increased the amount of weak acid sites, which enhanced the hydrolysis of hemicellulose. SO3H- ZSM-5 showed the highest catalytic activity followed by SO3H-SBA-15 while SO3H-ZrO2 exhibited a poor conversion. Furthermore, the catalytic hydrolysis of the hemicellulose leads to several interesting products, such as formic acid, acetic acid, lactic acid and xylan. The correlation between the catalytic performances and the acidic properties of the different samples indicates that the best catalytic performances were obtained with the least acidic solids and especially when the density of strong acid sites decreases.

碱预处理耦合三元DES体系对提高桉木组分分离效率的研究

本研究探索了一种氢氧化钾预处理耦合三元低共熔溶剂(DES)两段处理法,并用于分离桉木组分。首先采用单因素和Box-Behnken法优化了碱预处理分离桉木半纤维素的工艺条件,然后探究了碱预处理耦合三元DES两段处理桉木的微观形貌、比表面积、结晶度等。结果表明,优化后的氢氧化钾处理工艺条件为:处理温度76℃、处理时间5 h、氢氧化钾质量分数15%,此时半纤维素去除率可达(77.1±0.2)%。经碱预处理耦合三元DES(固液比1∶20(g∶mL)、反应时间30 min、反应温度90℃)两段处理后,桉木中纤维素、半纤维素和木质素形成的致密结构被打破,半纤维素去除率达83.3%,木质素去除率达96.5%,纤维素保留率达91.0%,比表面积和相对结晶度分别达0.9015 m^(2)/g和89.7%,显著提升了后续溶剂或生物酶的接触表面积。

半纤维素分解菌群HMC的微生物群落结构及功能

为明确半纤维素分解菌群HMC(hemicellulolytic microbial consortium)的微生物群落结构及其在半纤维素降解中的潜在功能;该研究测定了其在降解半纤维素主链木聚糖及玉米芯的典型理化指标,并利用16S rDNA测序技术及生物信息学手段对其微生物群落结构及功能注释进行了宏基因组学分析。结果表明,HMC在7 d内能高效降解木聚糖和玉米芯,降解率达80%,木聚糖降解产生的高值产物包括还原糖、甲酸、乳酸及乙酸,最高浓度分别为1.30、0.50、1.19与1.23 mg/mL,HMC降解玉米芯时可累积挥发性脂肪酸浓度高达3.54 mg/mL。HMC是由厚壁菌门Firmicutes的多个属的微生物组成的复合微生物菌群,宏基因组分析揭示了HMC在木聚糖降解过程中的关键碳水化合物活性酶系;HMC的半纤维素降解酶系完整,包括19个木聚糖分解及下游产物代谢相关的酶;同时涵盖了乙酸、乳酸等半纤维素关键分解产物代谢相关的通路。HMC蕴含半纤维素及玉米芯高值生物转化的潜力,该研究为深入探究半纤维素在生物降解应用中的分子机制提供了重要线索,有助于推动天然半纤维素生物降解技术的发展。