Hemicellulose Extraction Research Articles

The effect of non-structural components and lignin on hemicellulose extraction

As the important structural component of corn stover, hemicellulose could be converted into a variety of high value-added products. However, high quality hemicellulose extraction is not an easy issue. The present study aims to investigate the effects of non-structural components (NSCs) and lignin removal on alkaline extraction of hemicellulose. Although NSCs were found to have a minimal effect on hemicellulose dissolution, they affected the color values of the hemicellulose extracts. The lignin limited the hemicellulose dissolution and increased the color value by binding to hemicellulose molecules and forming lignin–carbohydrate complexes. Sodium chlorite method can remove about 90% lignin from corn stover, especially the lignin connected to hemicellulose through p-coumaric and ferulic acids. Which increased the hemicellulose dissolution ratio to 93% and reduced the color value 14–28%, but the cost is about 20% carbohydrates lost.

A precise study on effects that trigger alkaline hemicellulose extraction efficiency

The conversion of paper-grade pulps into dissolving pulps requires efficient strategies and process steps to remove low-molecular noncellulosic macromolecules generally known as hemicelluloses. Current strategies include alkaline extractions and enzymatic treatments. This study focused on the evaluation of extraction efficiencies in alkaline extractions of three economically interesting hardwood species: beech (Fagus sylvatica), birch (Betula papyrifera), and eucalyptus (Eucalyptus globulus). Substrate pulps were subjected to alkaline treatments at different temperatures and alkalinities using white liquor as the alkali source, followed by analyses of both pulps and hemicellulose-containing extraction lyes. The extracted hardwood xylans have strong potential as an ingredient in the food and pharmaceutical industries. Subsequent analyses revealed strong dependencies of the extraction efficiencies and molar mass distributions of hemicelluloses on the process variables of temperature and effective alkalinity. The hemicellulose content of the initial pulps, the hardwood species, and the type of applied base played minor roles.

Effects of hot water extraction pretreatment on physicochemical changes of Douglas fir

Hot water extraction (HWE) is an autocatalytic pretreatment that can be effectively integrated into most of the conversion technologies for extracting hemicelluloses from woody biomass. The objective of this study was to understand the influence of pretreatment factors on removal of hemicelluloses from Douglas fir chips. Compositional change in biomass was analyzed with ion chromatography and further confirmed with Fourier transform infrared spectroscopy (FT-IR). Highest hemicellulose extraction yield (HEY) was estimated to be 67.44% at the optimum reaction time (79 min) and temperature (180 °C) by using response surface methodology (RSM). Experimental results show that the HEY increased from 19.29 to 70.81% depending on the reaction time (30–120 min) and the temperature (140–180 °C). Effects of the severity factor (SF) on the mass removal and compositional changes were also evaluated. Hygroscopicity and thermal stability of wood were improved after HWE pretreatment. Colorimetric analysis showed that temperature has a greater influence on color of the wood chips during HWE pretreatment than dwell time. HWE pretreatment shows great potential for extracting hemicelluloses and altering physicochemical properties of wood in an integrated biorefinery for diversification of product portfolio.

Digestion of wood-based hemicellulose extracts as screened by in vitro gas production method and verified in vivo using sheep

The objective of the present study was to evaluate the potential of pressurized hot water extracted hemicellulose fractions from various wood species as feeds for ruminants. In Experiment 1, the fermentability of several hemicellulose extracts was screened using an in vitro gas production method. The samples were extracted from spruce (Picea abies) including mainly galactoglucomannan (GGM), from birch (Betula pendula) consisting mainly of xylan and from larch (Larix sibirica) consisting mainly of arabinogalactan. The GGM and xylan samples were readily fermented by rumen microbes while arabinogalactan was not. Based on the in vitro study, GGM was chosen for an in vivo digestibility trial using sheep, where it was fed at increasing proportions of diet dry matter (0, 47, 94 and 141 g kg-1) in a Latin Square design. The in vivo organic matter digestibility of GGM was relatively low, 0.58, but PHWE extracted hemicellulose has some potential as a feed for ruminants.

Optimal conditions for hemicelluloses extraction from Eucalyptus globulus wood: hydrothermal treatment in a semi-continuous reactor

Optimal conditions for hemicellulose extraction from wooden biomass in a semi-continuous system have been assessed in this work. This study would constitute the first stage for a profitable and green industrial process. Eucalyptus globulus was selected as raw material due to its low water consumption, high growth and its efficiency in lignocellulose production. Moreover its cultivation is very popular in southern Europe. Samples of 5.0g of wood were fractioned using a pressurized hot water semi-continuous system, to produce sugars (pentoses and hexoses) and a solid residue enriched in lignin.Five flow rates between 2.50 and 20.00mL/min and four temperatures between 135.0 and 285.0°C were tested in order to maximize the production of sugars, avoiding the formation of degradation products.Optimum conditions for the extraction of hemicellulose were identified at 185.0°C and 5.00mL/min, leading to a pentoses yield of 67.409wt%, with 0.702wt% of degradation products. Almost all the pulp is extracted at 285.0°C.SEM images show very well the changes in the wood structure at different temperatures.A kinetic model was developed, describing the extraction and hydrolysis of hemicellulose and cellulose with absolute average deviations around 10% for sugar extracted mass.

Effects of Removal of Chemical Components on Moisture Adsorption by Wood

To investigate the effects on moisture sorption behavior of wood caused by the removal of chemical components, Populus euramericana flour (40 to 60 mesh) was divided into four groups: untreated, extractives removed, hemicellulose removed, and matrix removed. The samples at the fiber saturation point and under oven-dried conditions were separately exposed to relative humidities of 11%, 45%, and 75% at 25 °C for desorption and adsorption. Additionally, moisture changes were measured during the processes. The results showed that moisture changed rapidly for all four groups at the initial stage during sorption, after which the rate gradually decreased until a steady-state equilibrium was reached. Among the four groups, the samples from which extractives had been removed exhibited the highest moisture content and moisture sorption coefficient, followed by the untreated samples, hemicellulose removed, and matrix removed samples. With increasing relative humidity, the hysteresis ratio A/D of the samples increased, indicating a reduction in sorption hysteresis, which was further decreased by hemicellulose extraction.

The hemicellulose extract from Cynara cardunculus: a source of value-added biomolecules produced by xylanolytic thermozymes

The hemicellulose fraction fromCynara cardunculuswas efficiently degraded and converted into xylo-conjugates by the thermophilic xylanolytic enzymatic systems ofGeobacillus thermantarcticus.

Selecting the Pre-Hydrolysis Conditions for Eucalyptus Wood in A Fractional Exploitation Biorefining Scheme

The operating conditions for the autohydrolysis of eucalyptus wood were optimized with a view to maximizing hemicellulose extraction while preserving the integrity of glucan. The influence of the operating conditions used in the soda–anthraquinone pulping of the solid phase resulting from the autohydrolysis process was examined. Autohydrolysis of the raw material at a liquid/solid ratio of 8 kg water/kg material at 180°C for 30 min was found to provide a commercially useful liquid phase containing most of the starting hemicellulose. The autohydrolysis treatment allowed the subsequent production of soda–anthraquinone cellulose pulp and paper with properties as good as or even better than those obtained without the pretreatment.

Microwave-assisted lime treatment and recovery of lignin from hydrothermally treated sweet sorghum bagasse

Microwave (MW)-assisted lime treatment was applied for the extraction of lignin from sweet sorghum bagasse (SSB) which was previously subjected to a MW-assisted hydrothermal treatment for the extraction of hemicellulose. Under optimum conditions, lime dosage at a concentration of 10% by weight of the substrate and 78 min of treatment residence time resulted in 68.27 (± 1.19) % by weight of the lignin extracted from the substrate. The residual SSB was composed of 69.41 (± 1.83) % cellulose, 12.14 (± 0.71) % hemicellulose, 12.59 (± 0.31) % lignin and 4.03 (± 0.21) % ash in it. The bulk density of the two-step treated SSB was 3.6 times that of the untreated SSB. The yellow liquor was treated with CO2 and 60.26 (± 2.11) % by weight of the dissolved lignin was precipitated from it. The physicochemical properties of the treated-SSB and the lignin samples were analysed using Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC) and scanning electron microscope (SEM). The mass balance of the MW-assisted fractionation of SSB was conducted and the prospect of the process for on-farm fractionation of lignocellulosic materials was considered.

Performance evaluation of a recycle-integrated process for the production and purification of monosaccharides from lignocellulosic biomass

Abstract Performance of a recycle-integrated process for producing monosaccharides from lignocellulosic biomass was investigated. The process combined continuous concentrated sulfuric acid hydrolysis of hemicellulose extract in a plug-flow reactor with single-column batchwise chromatographic fractionation of the resulting hydrolysates via sulfuric acid recycling. A pseudo-first order model with rate constants depending on proton and bisulfate concentrations was derived and successfully used to describe the hydrolysis kinetics. Sulfuric acid concentration was found to affect the process significantly. At a constant level of monosaccharide production rate, the hydrolysis reactor volume was found to decrease by 90% and the separation column volume increase by 76–130%, depending on the amount of monosaccharides in the feed, when sulfuric acid concentration was increased from 0.5 to 2.5 mol/L. However, at the same time, the difference between the equipment volumes decreased. The maximum monosaccharide productivity in the chromatographic separation decreased by 40%, and eluent consumption at the operating points giving these maxima increased by 33%, when the sulfuric acid concentration was increased from 0.5 to 2.5 mol/L. On the basis of the results, the studied process should be operated with 1.0–1.5 mol/L sulfuric acid.

How Does Alkali Aid Protein Extraction in Green Tea Leaf Residue: A Basis for Integrated Biorefinery of Leaves.

Leaf protein can be obtained cost-efficiently by alkaline extraction, but overuse of chemicals and low quality of (denatured) protein limits its application. The research objective was to investigate how alkali aids protein extraction of green tea leaf residue, and use these results for further improvements in alkaline protein biorefinery. Protein extraction yield was studied for correlation to morphology of leaf tissue structure, protein solubility and hydrolysis degree, and yields of non-protein components obtained at various conditions. Alkaline protein extraction was not facilitated by increased solubility or hydrolysis of protein, but positively correlated to leaf tissue disruption. HG pectin, RGII pectin, and organic acids were extracted before protein extraction, which was followed by the extraction of cellulose and hemi-cellulose. RGI pectin and lignin were both linear to protein yield. The yields of these two components were 80% and 25% respectively when 95% protein was extracted, which indicated that RGI pectin is more likely to be the key limitation to leaf protein extraction. An integrated biorefinery was designed based on these results.

Comparison of pulp species in IONCELL-P: selective hemicellulose extraction method with ionic liquids

Abstract In our recent studies, it was demonstrated that the IONCELL-P process selectively dissolves hemicelluloses from bleached birch kraft pulp in a mixture of 1-ethyl-3-methylimidazolium acetate ([emim][OAc]) and water as a solvent system. The IONCELL-P method refines paper-grade pulp to dissolving pulp with <5% hemicelluloses and allows isolation of polymeric xylan without yield losses or polymer degradation. This paper is a comparative study where paper-grade pine, birch, and eucalyptus pulps are subjected to the IONCELL-P process with two [emim]-based ionic liquids (ILs), i.e. [emim]acetate and [emim]dimethylphosphate. Also, the effect of an endoglucanase pretreatment was investigated to check whether 1) the pulp viscosity could be adjusted for the following process steps before the hemicellulose extraction and 2) the decreasing pulp viscosity would open the fiber structure and thus enhance the extraction. Under optimum conditions, the birch xylan content could be reduced from 25.4% down to 1.3% and for eucalyptus from 16.6% to 2.4%. Pine pulp xylan and glucomannan were decreased from 8.1% and 7.1% to 0.9% and 2.2%, respectively. The residual hemicellulose contents of the pine pulp could be further decreased with a hemicellulase pretreatment. The selectivity of the dissolution towards hemicelluloses was better for hardwoods. Adjusting the pulp viscosity by endoglucanase prior to the IONCELL-P process reduced the selectivity as short-chain cellulose molecules were extracted along with the hemicelluloses.

Life cycle assessment of an integrated forest biorefinery: hot water extraction process case study

AbstractThe environmental footprint of bioproducts depends on the performance and implementation strategy of the biorefinery processes through which they are produced. Life cycle assessment (LCA) studies are categorized into two general types: attributional and consequential. The consequential life cycle assessment (CLCA) method illustrates the change of flows to and from environment, resulting from different potential decisions. Depending on the analysis goal, CLCA is known to be the proper approach to address the environmental analysis of integrated biorefineries with multiple bioproducts.In this study, an LCA of hot water extraction‐based biorefinery strategy was performed, including five production pathways. Defined process options consisted of an extraction of hemicellulose to produce (i) biogas, (ii) hemicellulose for animal feed, (iii) hemicellulose for C5‐sugars, (iv) C5‐sugars, and (v) furfural. Except for the “biogas”, acetate salt was the by‐product of all the process options. Consequential LCA results proved that the bark consumption, chemicals, and bioproducts transportation have significant environmental impacts. ‘Hemicellulose for C5‐sugars’ and ‘C5‐sugars’ outperformed other alternative options with a greenhouse gas reduction of 80% and 68%, respectively. Also, normalized results of these two options presented remarkable improvement of more than three times in human health impacts in comparison to existing process at the case study mill. © 2015 Society of Chemical Industry and John Wiley & Sons, Ltd

Comparison of steam-assisted versus microwave-assisted treatments for the fractionation of sweet sorghum bagasse

The fractionation of lignocellulosic materials can be applied to get each of the components (cellulose, hemicellulose and lignin) of biomass in its maximum purity and yield. The individual component can be further processed to high-value products such as fuels and biomaterials at existing or newly developing biorefineries. The steam-assisted and microwave (MW)-assisted processes were used to fractionate sweet sorghum bagasse into hemicellulosic sugars, cellulose-rich and high-density residue and solid lignin. The treatment temperature evaluated for the fractionation process was 121 °C for 30 to 120 min. The substrate was autohydrolysed to extract the hemicellulose, and the residue was delignified using lime solution to obtain cellulose-rich residue. The lignin and lime from the liquor obtained after the lime treatment of the autohydrolysed sweet sorghum bagasse (SSB) was precipitated using carbon dioxide gas. Under optimum conditions, the steam-assisted autohydrolysis extracted 72.69 (±0.08) % by weight of the hemicelluloses while the MW-assisted autohydrolysis extracted 70.83 (±0.49) % of the hemicelluloses from the sweet sorghum bagasse. The steam-assisted lime treatment resulted in 69.67 (±1.26) % of the lignin extraction the MW-assisted lime treatment resulted in 68.27 (±1.19) % of the lignin extraction from the corresponding autohydrolysed sweet sorghum bagasse samples. The CO2 treatment precipitated 58.85 (±3.2) % of the lignin dissolved in the yellow liquor of the steam-assisted process while 60.26 (±2.11) % of the dissolved lignin was recovered from the yellow liquor of the MW-assisted process. The two methods have not exhibited significant differences in overall recovery of the solids, hemicellulose extraction, delignification, residual concentration of cellulose and ash or in the recovery of lignin and lime. The difference was significant (p value <0.05) only in the concentration of total reducing sugars in the hydrolysate and the yellow liquor. The MW-assisted process increased the total crystallinity index (TCI) of the cellulose in the treated SSB and also increased the concentration of guaiacyl lignin content in the recovered lignin which was thermally more stable than the lignin produced in the steam-assisted process.

Modifying solubility of polymeric xylan extracted from Eucalyptus grandis and sugarcane bagasse by suitable side chain removing enzymes

α-l-Arabinofuranosidase (AbfB) and novel α-d-glucuronidase (Agu1B) enzymes were applied for selective hydrolysis of beechwood (Fagus sylvatica) xylan (Sigma–Aldrich) as well as xylans extracted from Eucalyptus grandis and sugarcane (Saccharum officinarum L.) bagasse, leading to precipitation of these carbohydrate biopolymers. Hemicellulose extraction was performed with two mild-alkali methods, Höije and Pinto. Precipitation occurred after removal of 67, 40 and 16% 4-O-methyl-d-glucuronic acid (MeGlcA) present in polymeric xylans from beechwood, E. grandis (Pinto) and E. grandis (Höije), respectively. Precipitation was maximized at Agu1B levels of 3.79–7.53mg/gsubstrate and hemicellulose concentrations of 4.5–5.0% (w/v). Polymeric xylan from sugarcane bagasse precipitated after removal of 48 and 22% of arabinose and MeGlcA, respectively, at optimal AbfB and Agu1B dosages of 9.0U/g and 6.4mg/g, respectively. Both the purity of polymeric xylans and structure thereof had a critical impact on the propensity for precipitation, and morphology of the resulting precipitate. Nano-to micro-meter precipitates were produced, with potential for carbohydrate nanotechnology applications.

Emerging biorefinery technologies for Indian forest industry to reduce GHG emissions

The production of biofuels as alternative energy source over fossil fuels has gained immense interest over the years as it can contribute significantly to reduce the greenhouse gas (GHG) emissions from energy production and utilization. Also with rapidly increasing fuel price and fall in oil wells, the present scenario forces us to look for an alternative source of energy that will help us in the operation of industrial as well as the transportation sector. The pulp mills in India are one of the many options. The pulp mills in India can help us to produce bio-fuels by thermo-chemical/biochemical conversion of black liquor and wood residues. These technologies include extraction of hemi-cellulose from wooden chips and black liquor, lignin from black liquor, methanol from evaporator condensates, biogas production from waste sludge, syngas production from biomass using gasification and bio-oil production from biomass using pyrolysis. The objective of this paper is to overview these emerging bio-refinery technologies that can be implemented in Indian Forest Industry to get bio-fuels, bio-chemicals and bio-energy to reduce GHG emissions.

Hydrothermal fractionation of woody biomass: Lignin effect on sugars recovery

Subcritical water was employed to fractionate woody biomass into carbohydrates and lignin. Nine urban trees species (hardwood and softwood) from Spain were studied. The experiments were carried out in a semi-continuous reactor at 250°C for 64min. The hemicellulose and cellulose recovery yields were between 30%wt. and 80%wt. while the lignin content in the solid product ranged between 32%wt. and 92%wt. It was observed that an increment of solubilized lignin disfavored the hydrolysis of hemicelluloses. It was determined that the maximum extraction of hemicellulose was achieved at 20min of solid reaction time while the extraction of celluloses not exhibited a maximum value. The hydrolysis of hemicellulose and cellulose would be governed by the hydrolysis kinetic and the polymers accessibility. In addition, the extraction of hemicellulose was negatively affected by the lignin content in the raw material while cellulose hydrolysis was not affected by this parameter.

Sodium carbonate pre-extraction of bamboo prior to soda-anthraquinone pulping

A part of hemicelluloses is dissolved in black liquor during pulping process, which can be extracted prior to pulping, that would be used for producing biofuels, biopolymers, paper additives, and other chemicals in addition to pulp. However, the amount of hemicellulose extraction must be limited to maintain pulp yield and pulp quality. In this investigation, hemicelluloses were pre-extracted from bamboo with weak alkali (Na2CO3) and compared with hot water and dilute H2SO4 extraction prior to kraft, soda, and soda-anthraquinone (AQ) pulping. Bamboo chips were also pulped by the kraft process without pre-extraction. The biomass dissolution in weak alkaline pre-extraction was 11.1 %, which was 1.2 and 7.9 % lower than the hot water and dilute H2SO4 pre-extraction, respectively. In the alkaline pre-extraction process, 1.3 % lignin, 1.7 % acetic acid, and about 6.4 % sugars (on oven-dried mass of bamboo) were extracted. The soda-AQ process responded well in terms of pulp yield and pulp quality. Pulp yield after alkaline pre-extraction was higher and kappa number was lower than the hot water and dilute H2SO4 pre-extraction. Alkaline pre-extraction followed by kraft and soda-AQ pulping produced pulp with lower kappa number than non-extracted kraft pulp at almost similar pulp yield. This pulp showed better results in pre-bleaching with peroxyformic acid. Alkaline pre-extracted kraft and soda-AQ pulps had better tear index and slightly inferior tensile index than the non-extracted kraft pulp after D0EpD1 bleaching. Final brightness for soda-AQ and kraft pulp was 1.1 and 2.8 %, respectively, higher than the control pulp. Alkaline pre-extraction is a better option to integrate pulp mill with hemicellulose extraction and pulp production biorefinery.

Efficient extraction of bagasse hemicelluloses and characterization of solid remainder

To reduce the degradation of cellulose and obtain high molecular weight of hemicellulose from the extracts, pH pre-corrected hot water pretreatment was developed by employing sodium hydroxide (3.9mol/L). The response surface model was established to optimize the extraction process. The species composition and purity of hemicellulose extract was analyzed by High Performance Liquid Chromatography (HPLC). The obtained solid remainder was analyzed by FTIR and SEM. The results showed that the component of xylose in hemicellulose extract was similar with commercial xylan. FTIR and SEM were shown to be able to evaluate solid remainder composition and surface characterization of the bagasse. The biggest balance between solid remainder and dissolved solid was obtained. Not only the yield of dissolved solid was improved, but the structure of solid remainder was also proved, which was beneficial to pulping and papermaking.

Thermodynamic Insights in the Separation of Cellulose/Hemicellulose Components from Lignocellulosic Biomass Using Ionic Liquids

This work reports on the ionic liquid (IL) based separation of cellulose/hemicellulose from lignocellulosic biomass, by means of macroscale predictions using the COnductor like Screening MOdel for Real Solvents (COSMO-RS) model that is based on a statistical mechanical framework. For the benchmarking studies the experimental infinite dilution activity coefficient values for 13 components were predicted in 1-alkyl-3-methylimidazolium bis{(trifluoromethyl)sulphonyl}imide with an average absolute deviation (%AAD) of 15 %. Further, the solid–liquid equilibria of glucose, fructose, galactose, and xylose in [EMIM][EtSO4] and Aliquat®336 were predicted successfully with 15 % root-mean-square deviation. Afterwards, the selectivities were predicted at infinite dilution for cellulose/hemicellulose in 1,156 ILs with a combination of 34 cations and 34 anions. Based on these values, the ammonium-based ILs 1-methyl-4-aminotriazolium hexafluorophosphate [14MATAZ][PF6] and 4-aminotriazolium bis(oxalato(2)borate) [4ATAZ][BOB] were found to be good candidates for cellulose and hemicellulose extraction, respectively. The ILs selected using the COSMO-RS methodology were then studied qualitatively in terms of interaction energies and HOMO–LUMO energy gap. The binding energy for [1-methyl-4-aminotriazolium][PF6] + cellulose and [4-aminotriazolium][BOB] + cellulose systems are higher as compared with IL + cellulose + hemicellulose, indicating greater stability.