Hemicellulose Extraction Research Articles

A comparative study of hemicellulose isolation with hot water, alkaline, and delignification methods from tea leaf brewing waste

Tea leaf brewing waste (TLBW) is a waste with high hemicellulose content. It is a valuable waste of the pharmaceutical and cosmetics industry especially the beverage industry. In this study, the extraction of hemicelluloses (HC) from tea leaf brewing waste using three different pretreatment methods were investigated. The isolation yield of the HC was determined depending on pretreatment methods and pretreatment parameters such as the isolation temperature (25–55 °C), alkaline concentration (NaOH, 5–20%), contact time (12–24 h), the oxidative component (H2O2), and the concentration of sodium chlorite (NaCIO2) in the solution (2–10%). It was observed that the yield of isolation of hemicellulose varied between about 1 and 36% on the basis of raw materials depending on the extraction parameters. The experimental results showed that the suitable conditions for isolation of hemicellulose by alkaline pretreatment method were 15% NaOH concentration, 12-h contact time, and 45 °C. As a result of the experiments performed with the most suitable conditions, approximately 96% of the total hemicellulose in the TLBW was isolated. The extraction yield of hemicellulose achieved by the delignification process was found to be lower about 3% compared with the alkaline methods. But, the hemicellulose color achieved by the delignification process was lighter in color than the alkaline method. The results of the FTIR and H-NMR analysis show that the purity of the hemicellulosic fraction, which was obtained using the delignification method, was higher than the alkaline method.

Oriented strand board with improved dimensional stability by extraction of hemicelluloses

Oriented strand board (OSB) panels are commonly used for wooden building structures such as Walls, floors, ceilings, and furniture. These wood composites are manufactured with small wooden strands held together in specific orientations by adhesives. Other additives such as wax might be added to reduce water absorption. One of the limitations of the panels produced today is their poor performance under high humidity conditions. The goal of the present work was 1) to extract hemicelluloses from pine wood strands before the fabrication of OSB panels and 2) to test the impact of the pretreatment on the dimensional stability of these panels. For that purpose, pressure-assisted hydrothermal processes at three different temperatures (120, 140, and 160 o C) were performed for 45 min of extraction time in each case. Hemicelluloses in treated wood strands were quantified using high-performance liquid chromatography. Water absorption, thickness swell, MOE, MOR, and internal bond strength were measured to assess the influence of the pretreatment on OBS properties. According to the results, a hydrothermal pretreatment is beneficial for the performance of OSB panels at high humidity levels. The pretreatment of pine strands at 160 o C allowed for the maximum removal of hemicelluloses, without a significant degradation of cellulose or lignin, and the OSB panels pretreated with these pinewood strands displayed the best performance in dimensional stability under wet conditions.

Effect of sequential acid-alkaline treatment on physical and chemical characteristics of lignin and cellulose from pine (Pinus spp.) residual sawdust

Timber industry generates large amounts of residues such as sawdust. Softwoods have a significant economic value for timber production and the Pinus genus is widely utilized. Thus, the aim of this work was to study the hemicellulose extraction and lignin recovery from pine (Pinus spp.) residual sawdust (PRS) by sequential acid-alkaline treatment, generating a cellulose-rich solid fraction. The hemicellulose removed was 87.11% (wt·wt−1) after dilute acid treatment at 130 °C, 4.5% (wt·wt−1) of H2SO4 for 20 min at 120 rpm. Three temperatures were evaluated for recovering the lignin and the highest yield, 93.97% (wt·wt−1), was achieved at 170 °C, 10% (wt·wt−1) of NaOH for 90 min at 120 rpm. Lignin was characterized by Fourier-transform infrared spectroscopy, nuclear magnetic resonance and thermogravimetry. The resulting cellulose-rich fraction exhibited polymorphic transformation. The results demonstrated that PRS is a promising lignocellulosic residue whose lignin and carbohydrates can be readily obtained.

Effect of autohydrolysis on hemicellulose extraction and pyrolytic hydrogen production from Eucalyptus urograndis

Ensuring environmental and social-economic sustainability in the use of materials from lignocellulosic biomass requires their fractionation and valorization of their main components. In this work, we used Eucalyptus urograndis wood to obtain chemicals and energy. The raw material was characterized in chemical terms and then subjected to autohydrolysis under variable operating conditions to optimize the extraction of hemicellulose derivatives relative to cellulose. The kinetics of the pyrolysis process was modeled in terms of activation energy and hydrogen production. Using temperatures in the range of 180–190 °C and treatment times in the range of 15–30 min allowed more than 74.5% of all hemicellulosic components in the raw material to be selectively extracted into the liquid post-hydrolysis phase, more than 90% of all glucan to remain in the solid phase and up to 27.8% of lignin to be removed. The thermal behavior of solid fraction was examined by thermogravimetric analysis, using variable heating rates under a nitrogen atmosphere, and the activation energy can be estimated by using the Flynn-Wall-Ozawa method. Based on the results, the pyrolysis of E. urograndis can be modeled as a first-order reaction. The activation energy (Ea) at a fractional conversion α between 0.3 and 0.7 was 183 to 199 KJ mol−1 for the raw material, whereas that for the solid residue from autohydrolysis ranged from 179 to 186 kJ mol−1 at same fractional conversion when operational temperature in autohydrolysis was upper 185 °C. Based on the results, using temperatures above 180 °C and times of 15 min or longer [i.e., operating at the (0,0) experimental point for the autohydrolysis process] in combination with degrees of conversion from 0.3 to 0.8 reduced the activation energy of the pyrolysis process in relation to the raw material by up to 12% and removed hemicellulose by more 74.5% from it. In parallel, the comparative analysis of the Ea values and the composition of the pyrolysis gas obtained showed a negative relationship between Ea and the amount of hydrogen produced.

Hemicellulose Extraction and Characterization of Rice Straw and Leucaena Leucocephala

Local production of agricultural waste is increasing. It is not fully utilized and can cause an environmental issue if it is not handle wisely. Thus, it is important to increase utilization of lignocellulosic biomass by improving their added value and subsequently decrease the agriculture waste. In this study, rice straw and Leucaena leucocephala were subjected to alkali treatment (4% sodium hydroxide) with different concentration ratio of samples to sodium hydroxide (1:10 to 1:50). The physical and chemical properties of extracted hemicelluloses were studied. The yield of hemicellulose was higher from rice straw compared to Leucaena leucocephala. The chemical functional groups present in hemicellulose were confirmed by Fourier tranform infrared spectroscopy (FTIR). The surface morphology and roughness of xylan were examined by scanning electron microscopy (SEM).
 Keywords: rice straw, hemicellulose, sodium hydroxide, alkali

Effect of pH on hemicellulose extraction and physicochemical characteristics of solids during hydrothermal pretreatment of eucalyptus

The effects of pH on residual solids (RS), total dissolved solids (TDS), carbohydrates, and lignin in eucalyptus during hydrothermal pretreatment were studied. The balance between RS and TDS was obtained at pH 4.0 in hydrothermal pretreatment with pre-adjustment pH. The yield of hemicellulose increased, and oligosaccharides dominated. Hemicellulose had the highest dissolution rate, and cellulose and lignin had the lowest dissolution rate at pH 4.0. The crystallinity index (CrI) and structural transformation of lignin was analyzed by X-ray diffraction (XRD) and nuclear magnetic resonance spectroscopy (NMR) with or without pretreatment. The CrI at pH 4.0 was 64.2% higher than that with the traditional hydrothermal pretreatment (62.1%). The β-O-4 bonds, OMe, and phenylcoumarane of lignin were protected. The highest hemicellulose extraction and minimal physicochemical structural changes were obtained at pH 4.0.

Impact of Pretreatment on Hydrothermally Carbonized Spruce

Upgrading biomass waste streams can improve economics in wood industries by adding value to the process. This work considers use of a hydrothermal carbonization (HTC) process for the residual feedstock after lignin and hemicelluloses extraction. Batch experiments were performed at 200–240 °C temperatures and three hours residence time with an 8:1 biomass to water ratio for two feedstocks: Raw spruce and spruce after lignin extraction. The proximate analysis and heating value showed similar results for both feedstocks, indicating that the thermochemical conversion is not impacted by the removal of lignin and hemicelluloses; the pretreatment processing slightly increases the heating value of the treated feedstock, but the HTC conversion process produces a consistent upgrading trend for both the treated and untreated feedstocks. The energy yield was 9.7 percentage points higher for the treated wood on average across the range temperatures due to the higher mass yield in the treated experiments. The energy densification ratio and the mass yield were strongly correlated with reaction temperature, while the energy yield was not. Lignocellulosic composition of the solid HTC product is mainly affected by HTC treatment, the effect of lignin extraction is negligible.

Alkali-peroxide treatment of sugar cane bagasse. Effect of chemical charges on the efficiency of xylan isolation and susceptibility of bagasse to saccharification

Sugar cane is a promising raw material for the extraction of hemicelluloses. An alkali treatment of sugar cane bagasse under proper conditions followed by a precipitation using a reasonable quantity of ethanol can be an effective method to isolate these polysaccharides. In this work, bagasse is treated to obtain two products: (a) polymeric hemicellulose and (b) an enzymatic hydrolysate from the treated bagasse after hemicellulose extraction. The effects of charges of sodium hydroxide (10, 20, 40% w/w) and hydrogen peroxide (0, 10, 20% w/w) in the alkali treatment were evaluated. A 32 experimental design was considered under control of metal ions and inert atmosphere during alkaline treatment. An acceptable proportion of xylose plus arabinose could be extracted from bagasse (up to 18.4 g/100 g of bagasse). Both the alkali and peroxide showed strong effects on the yield of the extraction, as well as on the yield of the precipitation in ethanol-water solution. Besides, the susceptibility of bagasse for cellulolytic enzymatic hydrolysis is improved. The highest hemicellulose precipitation yield was 85% which corresponded to the treatment with the highest alkali charge without peroxide. The highest yield of enzymatic hydrolysis was obtained for the highest alkali and peroxide charges.

Techno‐Economic Analysis for Production of L‐Arabitol from L‐Arabinose

AbstractThe process design for synthesis of arabitol by hydrogenation of arabinose on a supported ruthenium catalyst is described. Aspen HYSYS software was used to design an arabitol production plant for subsequent generation of hydrogen through aqueous phase reforming (APR). The process design included hydrogen recycling requiring a flash drum and recompression. The total costs of arabitol were estimated to be substantially dependent on the feedstock costs and are closely related to arabinose feed cost. Feasible production of hydrogen using APR requires efficient extraction of hemicellulose from lignocellulosic biomass and subsequent hydrolysis.

Effect of Pre-Corrected pH on the Carbohydrate Hydrolysis of Bamboo during Hydrothermal Pretreatment.

To confirm the prospects for application of pre-corrected pH hydrothermal pretreatment in biorefineries, the effects of pH on the dissolution and degradation efficiency of carbohydrates were studied. The species composition of the hydrolysate was analyzed using high efficiency anion exchange chromatography and UV spectroscopy. The result showed that the greatest balance between the residual solid and total dissolved solids was obtained at pH 4 and 170 °C. Maximum recovery rates of cellulose and lignin were as expected, whereas hemicellulose had the least recovery rate. The hemicellulose extraction rate was 42.19%, and the oligomer form accounted for 93.39% of the product. The physicochemical properties of bamboo with or without pretreatment was characterized. Compared with the traditional hydrothermal pretreatment, the new pretreatment bamboo has higher fiber crystallinity and thermal stability. In the pretreatment process, the fracture of β-aryl ether bond was inhibited and the structural dissociation of lignin was reduced. The physicochemical properties of bamboo was protected while the hemicellulose was extracted efficiently. It provides theoretical support for the efficient utilization of all components of woody biomass.

Efficient Extraction and Structural Characterization of Hemicellulose from Sugarcane Bagasse Pith.

The aim of this study was to investigate the ultrasound-assisted alkaline extraction process and structural properties of hemicellulose from sugarcane bagasse pith. Response surface model (RSM) was established in order to optimize the extraction conditions for the highest hemicellulose yield based on the single-factor experiments. A maximum total hemicellulose yield of 23.05% was obtained under the optimal conditions of ultrasonic treatment time of 28 min, KOH mass concentration of 3.7%, and extraction temperature of 53 °C, and it evidently increased 3.24% compared without ultrasound-assisted extraction. The obtained hemicellulose was analyzed by Fourier transform infrared (FT-IR) spectroscopy. The monosaccharide composition and average molecular weight of hemicellulose were characterized by using ion chromatography (IC) and gel permeation chromatography (GPC). The results indicated that xylose was dominant component in water-soluble hemicellulose (WH, 69.05%) and alkali-soluble hemicellulose (AH, 85.83%), respectively. Furthermore, the monosaccharides (otherwise xylose) and uronic acids contents of WH were higher than that of AH. Weight average molecular weight of WH was 29923 g/mol, lower than that of AH (74,872 g/mol). These results indicate that ultrasonic-assisted alkaline extraction is an efficient approach for the separation of hemicellulose from sugarcane bagasse pith.

Comparison of single-stage and two-stage hydrothermal pretreatments for improving hemicellulose separation from bamboo chips

In this work, a simple two-stage pretreatment (TSP) was utilized to improve hemicellulose separation and alleviate lignin condensation and therefore facilitate hemicellulose extraction and subsequent kraft pulping. In contrast to single-stage pretreatment, TSP showed a significant improvement for hemicellulose extraction and hemicellulose degradation and provided an almost identical cellulose loss. The hemicellulose separation efficiency was significantly improved using TSP with 60 min first followed by 30 min. More importantly, proper pretreatment is beneficial to the subsequent delignification; extensive pretreatment can retard delignification.

Rhodotorula toruloides Single Cell Oil Production Using Eucalyptus urograndis Hemicellulose Hydrolysate as a Carbon Source

Microbial oil is a potential substitute for vegetable oils in the biodiesel industry. Efforts to obtain cheap carbon sources for the cultivation of lipid-producing microorganisms comprise an active research area. This work aimed to extract the hemicellulose fraction from Eucalyptus uograndis and to use its hydrolysate as a carbon source for Rhodotorula toruloides (an oleaginous yeast) cultivation for microbial oil production. Hemicellulose hydrothermal extractions were performed at different temperatures, times, and ratios of solid to liquid (S/L). Temperature and time showed a stronger effect on the solubilization of hemicellulose. Hemicellulose extraction at 155 °C, 195 min, and an S/L ratio of 1/2 resulted in a hydrolysate with a xylose content of 37.0 g/l. R. toruloides cultivation in this hydrolysate showed that initial pH had a strong influence on cell growth. At an initial pH of 6.2, cells grew to 6.0 g/l of biomass with a lipid content of 50%. Therefore, we believe that E. urograndis hemicellulose hydrolysate could be a potential substrate for R. toruloides for lipid production based on the biorefinery concept.

Green Protocols for the Isolation of Carbohydrates from Vineyard Vine-Shoot Waste

Annually large amounts of vineyard waste are produced from vine pruning. Romania has a vineyard of 183,000 ha and produces 6.0 million hl of wine/annum, being ranked 10th in the world and 5th in Europe, after Spain, France, Italy, and Portugal. Currently, the waste is incorporated into the soil or burned in open field, leading to increased greenhouse gas emissions. The extraction of cellulose, hemicellulose, and lignin from vine-shoot waste is a primordial step for the integral valorization of these resources. The study aims to obtain carbohydrates from vine-shoot waste from Romanian grape varieties by using an innovative method for the transformation of vine-shoot waste into valuable compounds. Microwave pretreatments were performed using different operational conditions: temperature (150–180 °C) and residence time (10–30 min). The pretreated vine-shoot waste was delignified with sodium chlorite for lignin removal and then enzymatically hydrolyzed using new types of enzymes (cellulase from Trichoderma reesei and β-glucosidase). A maximum of 14 g glucose can be obtained from 100 g vine-shoot waste by microwave pretreatment (165 °C for 20 min), delignification, and enzymatic hydrolysis for 80 h. It can be concluded that the vine-shoot waste may be used as a raw material for bioethanol production by using a green technology in the context of circular economy objectives.

A new surfactant assisted acid prehydrolysis process for enhancing biomass pretreatment

Prehydrolysis is an essential step for utilizing biomass, particularly in the Kraft-based dissolving pulp process. Once the hemicellulose was effectively extracted, it can not only upgrade the dissolving pulp, but also arise additional revenue by converting value-added products. Herein, sodium dodecyl benzene sulfonate (SDBS) was used to enhance the hemicellulose removal from poplar wood chips during mild acid hydrolysis. SDBS addition could reduce the surface tension, thus increasing the diffusion of hydrogen ion and promoting the hemicellulose and lignin dissolution. The hemicellulose removal was increased from 42.5 to 54.7% by adding SDBS in comparison with the control under condition of 170 °C and 2 h. Additionally, the lignin removal was increased from 9.6 to 19.1%. Gel permeate chronograph, scanning electron microscope, and heteronuclear single quantum coherence spectroscopy support the positive effect of SDBS addition. The properties of dissolving pulp prepared from surfactant assisted pretreatment are comparable/better than that derived from acid pretreatment. It opened a sustainable and economical way to extract hemicellulose from lignocellulose. A new surfactant assisted acid prehydrolysis process for enhancing biomass pretreatment.

Lignin-Rich PHWE Hemicellulose Extracts Responsible for Extended Emulsion Stabilization.

Wood hemicelluloses have an excellent capacity to form and stabilize oil-in-water emulsions. Galactoglucomannans (GGM) from spruce and glucuronoxylans (GX) from birch provide multifunctional protection against physical breakdown and lipid oxidation in emulsions. Phenolic residues, coextracted with hemicelluloses using the pressurized hot water (PHWE) process, seem to further enhance emulsion stability. According to hypothesis, phenolic residues associated with hemicelluloses deliver and anchor hemicelluloses at the emulsion interface. This study is the first to characterize the structure of the phenolic residues in both GGM- and GX-rich wood extracts and their role in the stabilization of emulsions. PHWE GGM and GX were fractionated by centrifugation to obtain concentrated phenolic residues as one fraction (GGM-phe and GX-phe) and partially purified hemicelluloses as the other fraction (GGM-pur and GX-pur). To evaluate the role of each fraction in terms of physical and oxidative stabilization, rapeseed oil-in-water emulsions were prepared using GGM, GX, GGM-pur, and GX-pur as stabilizers. Changes in droplet-size distribution and peroxide values were measured during a 3-month accelerated storage test. The results for fresh emulsions indicated that the phenolic-rich fractions in hemicelluloses take part in the formation of emulsions. Furthermore, results from the accelerated storage test indicated that phenolic structures improve the long-term physical stability of emulsions. According to measured peroxide values, all hemicelluloses examined inhibited lipid oxidation in emulsions, GX being the most effective. This indicates that phenolic residues associated with hemicelluloses act as antioxidants in emulsions. According to chemical characterization using complementary methods, the phenolic fractions, GGM-phe and GX-phe, were composed mainly of lignin. Furthermore, the total carbohydrate content of the phenolic fractions was clearly lower compared to the starting hemicelluloses GGM and GX, and the purified fractions GGM-pur and GX-pur. Apparently, the phenolic structures were enriched in the GGM-phe and GX-phe fractions, which was confirmed by NMR spectroscopy as well as by other characterization methods. The frequency of the main bonding pattern in lignins, the β-O-4 structure, was clearly very high, suggesting that extracted lignin remains in native form. Furthermore, the lignin carbohydrate complex of γ-ester type was found, which could explain the excellent stabilizing properties of PHWE hemicelluloses in emulsions.

Techno‐economic analysis of hemicellulose extraction from different types of lignocellulosic feedstocks and strategies for cost optimization

AbstractHemicellulose is a polymer found abundantly in lignocellulosic feedstocks, with many potential market applications. However, there has yet to be a large‐scale commercial process to isolate hemicellulose from lignocellulosic biomass. A techno‐economic assessment for hemicellulose extraction from sugarcane bagasse, switchgrass, and poplar was made. Two isolation processes after alkaline extraction were considered: (1) producing total hemicellulose and (2) producing hemicellulose A (water‐insoluble fraction) only. In a greenfield scenario, a byproduct of the process is sugar, whereas in a co‐location scenario the biomass after hemicellulose extraction is returned to the pulp mill for its fiber value. Operating costs, capital investment, minimum hemicellulose selling price (MHSP), the effect of input material and product prices along with several other process parameters on the MHSP were determined for each scenario. Co‐location scenarios had a dramatically lower capital cost and MHSP relative to greenfield scenarios. This was due to co‐location scenarios utilizing existing biomass processing and utilities equipment and not requiring a sugar‐production process. Among the three biomasses, hemicellulose extraction from sugarcane bagasse had the lowest MHSP for all scenarios, mainly due to a higher hemicellulose extraction yield. Extraction of hemicellulose A from sugarcane bagasse in a co‐location scenario had a low capital cost of 56 million USD and had a reasonable MHSP of 274 USD/t (metric ton). This research indicates that there is reasonable economic potential for hemicellulose extraction from lignocellulosic biomass for applications to replace starch or as a starting material for the production of xylo‐oligomeric prebiotics. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd

Optimising wheat straw alkali-organosolv pre-treatment to enhance hemicellulose modification and compatibility with reinforcing fillers

Hemicellulose acetylation, filler compatibility and film hydrophobicity were enhanced by optimising alkali-catalysed organosolv treatment conditions for wheat straw before hemicellulose extraction. Two optimum (OPT) conditions were established by varying organosolv components’ concentrations [ethanol (EC) (50–80%) and NaOH (1–13%)], and time (2–6 h), in a Box-Behnken experimental design. The OPT1 (1% NaOH/50% EC/6h) that enhanced acetylation and filler compatibility, and OPT2 (13% NaOH/80% EC/5h) that enhanced hydrophobicity by minimising degree of acetylation (DS), uronic acid content and arabinose/xylose ratio. The films made from OPT2 hemicellulose had higher water contact angle (68.1°) than OPT1 hemicellulose (39.90°). However, OPT1 hemicellulose had a higher DS (1.7 vs 0.4), and their acetylated nanocellulose reinforced films had higher tensile strength (10.59 vs 4.87 MPa) and Young modulus (590.15 vs 323.64 MPa) than OPT2 hemicellulose. Therefore, hemicellulose acetylation, hydrophobicity and filler interaction can be engineered by manipulating the organosolv treatment conditions.

Steam explosion pre-treatment of alkali-impregnated lignocelluloses for hemicelluloses extraction and improved digestibility

The application of steam explosion pre-treatment to extract xylan-rich biopolymers from alkali-impregnated lignocelluloses, while simultaneously increasing the enzymatic digestibility of cellulose, was investigated. Steam-enhanced extraction of xylan from sugarcane trash (SCT) and aspen wood (AW) was performed at varying temperatures (176–204 °C) and retention times (3–17 min) after the impregnation of biomass samples with sodium hydroxide at 1:20 (w/w) solid loading ratio. Xylan extraction and cellulose digestibility results were statistically analysed to fix the condition/s for significantly enhanced values. Accordingly, maximum xylan yields of 51 and 24%, and highest cellulose digestibility of 92 and 81%, were attained for SCT and AW respectively following their pre-treatment at 204 °C for 10 min. At this most-severe condition, neither xylose nor furfural – a degradation product from xylose – were observed in the hemicellulose extract, indicating steam explosion pre-treatment with alkali impregnation of lignocelluloses as viable biorefinery approach to co-produce xylan biopolymers and bioethanol.

C-O Bond Hydrogenolysis of Aqueous Mixtures of Sugar Polyols and Sugars over ReOx-Rh/ZrO2 Catalyst: Application to an Hemicelluloses Extracted Liquor

The recovery and upgrade of hemicelluloses, a family of heteropolysaccharides in wood, is a key step to making lignocellulosic biomass conversion a cost-effective sustainable process in biorefinery. The comparative selective catalytic C-O bond hydrogenolysis of C5-C6 polyols, sugars, and their mixtures for the production of valuable C6 and C5 deoxygenated products was studied at 200 °C under 80 bar H2 over ReOx-Rh/ZrO2 catalysts. The sugars were rapidly converted to the polyols or converted into their hydrogenolysis products. Regardless of the reactants, C-O bond cleavage occurred significantly via multiple consecutive deoxygenation steps and led to the formation of linear deoxygenated C6 or C5 polyols. The distribution of products depended on the nature of the substrate and C-C bond scission was more important from monosaccharides. In addition, we demonstrated effective hydrogenolysis of a hemicellulose-extracted liquor from delignified maritime pine containing monosaccharides and low MW oligomers. Compared with the sugar-derived polyols, the mono- and oligosaccharides in the liquor were more rapidly converted to hexanediols or pentanediols. C-O bond scission was significant, giving a yield of desired deoxygenated products as high as 65%, higher than in the reaction of the synthetic mixture of glucose/xylose of the same C6/C5 sugar ratio (yield of 30%).