Hemicellulose Extraction Research Articles

Study on the hydrothermal gradient extraction of hemicellulose by a flow-through reactor

The hydrothermal gradient extraction process based on the hemicellulose constituent units is important for obtaining high quality hemicellulose products. The hydrothermal extraction of sawdust hemicellulose was performed under both non-isothermal and isothermal operations using a flow-through reactor for investigating the extraction patterns. The results show that there were significant differences in the major forms of hemicellulose units at different extraction stages. For glucose, xylose, and galactose units, the selectivity of oligomeric form decreased gradually with increasing temperature, whereas it decreased and then increased under thermostatic operation. The selectivity of the mannose oligomeric form decreased and then increased in both operation modes, reaching a trough at 170 °C (96.81 %) and 60 min (55.21 %), respectively. The molecular weight of extracted hemicelluloses were mainly distributed below 70,000 Da, and gradually decreased with temperature, but increased with time. The results contribute to the quantitative and qualitative understanding of the hemicellulose gradient extraction process.

Effects of peracetic acid delignification on hemicellulose extraction by dimethyl sulfoxide

Extracting high-purity and structurally intact hemicelluloses from lignocellulosic fibers is a prerequisite to reveal their structures and realize high-value utilization. Delignification is usually performed before hemicellulose extraction to break the covalent bonds between hemicelluloses and lignin for effective separations, but usually leads to toxic by-products and hemicellulose degradation. Peracetic acid (PAA) is an environmentally friendly oxidizing agent, which is more selective for delignification and has less effect on the primary structure of hemicelluloses. However, the yields and chemical structures of hemicelluloses extracted at different PAA delignification conditions are not clear, which greatly hinders its research and application. Consequently, the response surface methodology (RSM) was used in this study to optimize the process parameters of PAA delignification. With the increase of temperature or time, the yield of holocellulose decreases, and the hemicellulose yield increases first and then decreases. With the increase of delignification degree, the hemicellulose yield increases significantly. The degree of PAA delignification also has a significant effect on the chemical structures of extracted hemicelluloses; hemicellulose samples extracted from highly delignified holocelluloses have a higher xylose unit content, molecular weight (MW) and degree of substitution by acetyl groups (DSAc). The tert-butanol solvent exchange or ball milling treatments on holocelluloses significantly increase the hemicellulose yields, by avoiding the hornification and improving the accessibility of holocellulose. This study will provide theoretical and technical support for the efficient separation of hemicelluloses.

Extraction of cell wall pectins and hemicellulose from agro-industrial wastes: A sustainable alternative source

The efficient repurposing of agro-industrial waste has significantly enhanced the utilization of food resources. This study aims to propose a methodology for extracting cell wall polysaccharides from residues of mango (Mangifera indica), passion fruit (Passiflora edulis), and cashew (Anacardium occidentale). Polysaccharide fractions were obtained through sequential extraction protocols involving water, cyclohexane-trans-1,2-diamine tetracetate (CDTA), sodium carbonate:CDTA, and potassium hydroxide. These fractions were categorized as water-soluble pectin (WSP), CDTA-soluble pectin (CSP), sodium carbonate-soluble pectin (SSP), and hemicellulose (HC), respectively. Each polysaccharide fraction was characterized by Nuclear Magnetic Resonance (NMR) spectroscopy and Gel Permeation Chromatography (GPC). Monosaccharide composition was determined using Gas Chromatography-Mass Spectrometry (GC–MS). NMR spectra of WSP, CSP, and SSP fractions exhibited characteristic pectin features, while the HC fraction primarily comprised hemicellulose. Consequently, the proposed methodology demonstrates potential as a standardized protocol for the extraction of pectin and hemicellulose from various food sources.

Effects of alkali-soluble hemicellulose separation on the structure of bamboo lignin and lignin-carbohydrate complexes

In this study, alkali treatment was used to preferentially separate hemicellulose, and the structural changes of lignin and lignin-carbohydrate complexes (LCC) in the residual bamboo solids were investigated. The chemical composition and structural characteristics of lignin and LCC were analyzed. After alkali treatment, the monosaccharide content in bamboo lignin decreased from 7.62 % to 2.90 % compared to the raw material. The obtained lignin exhibited higher purity and larger molecular weight, with the macromolecular lignin linked by β-O-4′ bonds remaining almost undegraded. After alkali treatment, the linkage bonds in the Björkman LCC were composed of phenyl glycoside (PhGlc), and the bond in LCC-AcOH consisted of benzyl ether (BE). The results showed that the preferential extraction of hemicellulose preserved the biopolymer structure of lignin in bamboo, thereby providing an important basis for the comprehensive separation and utilization of bamboo components.

Organic Acid-Based Hemicellulose Fractionation and Cellulosic Ethanol Potential of Five Miscanthus Genotypes

The pretreatment of lignocellulosic biomass such as Miscanthus grown on marginal agricultural land is very challenging and requires severe conditions to fractionate cell wall polymers for further valorization. The current study aimed to determine organic acid-based mild conditions to pretreat contrasting lignocellulosic Miscanthus genotypes for the efficient fractionation of cell wall components, with special focus on hemicellulose extraction. In doing so, five Miscanthus genotypes were subjected to four different acid treatments (sulfuric acid, oxalic acid, malonic acid, and citric acid) in a vertical high-pressure steam sterilizer. The results demonstrated that, among the organic acids, oxalic acid was identified as the most effective pretreatment solvent for hemicellulose separation, whereas citric acid yielded the highest amount of galacturonic acid, varying from 15 to 17 mg mL−1 across genotypes. One best performing genotype was selected for the enzymatic hydrolysis. Overall, M. floridulus genotypes exhibited the optimal quality traits for efficient bioconversion with second best in terms of ethanol production potential.

Arabinoxylo-oligosaccharides production from unexploited agro-industrial sesame (Sesamum indicum L.) hulls waste

This work demonstrates that sesame (Sesamum indicum L.) hull, an unexploited food industrial waste, can be used as an efficient source for the extraction of hemicellulose and/or pectin polysaccharides to further obtain functional oligosaccharides. Different polysaccharides extraction methods were surveyed including alkaline and several enzymatic treatments. Based on the enzymatic release of xylose, arabinose, glucose, and galacturonic acid from sesame hull by using different enzymes, Celluclast®1.5 L, Pectinex®Ultra SP-L, and a combination of them were selected for the enzymatic extraction of polysaccharides at 50 °C, pH 5 up to 24 h. Once the polysaccharides were extracted, Ultraflo®L was selected to produce arabinoxylo-oligosaccharides (AXOS) at 40 °C up to 24 h. Apart from oligosaccharides production from extracted polysaccharides, alternative approaches for obtaining oligosaccharides were also explored. These were based on the analysis of the supernatants resulting from the polysaccharide extraction, alongside a sequential hydrolysis performed with Celluclast®1.5 L and Ultraflo®L of the starting raw sesame hull. The different fractions obtained were comprehensively characterized by determining low molecular weight carbohydrates and monomeric compositions, average Mw and dispersity, and oligosaccharide structure by MALDI-TOF-MS. The results indicated that sesame hull can be a useful source for polysaccharides extraction (pectin and hemicellulose) and derived oligosaccharides, especially AXOS.

Valorization of rice straw and vascular aquatic weeds for sustainable prebiotic hemicellulosic autohydrolysate production: Extraction, characterization and fermentability.

This study describes the extraction and characterization of the hemicellulosic autohydrolysates (HAHs) derived from rice straw (RS) and vascular aquatic weeds like Typha angustifolia (TA) and Ceretophyllum demersum (CD). It further explores their capacity to sustain the proliferation of selected lactic acid bacteria (i.e., prebiotic activity) isolated from milk samples. To fractionate HAH from RS, TA and CD hot water extraction (HWE) method was used and RS, TA, and CD biomasses yielded 6.8, 4.99 and 2.98% of HAH corresponding to the hemicellulose extraction efficiencies of 26.15 ± 0.8%, 23.76 ± 0.6%, and 18.62 ± 0.4% respectively. The chemical characterization of HAH concentrates through HPLC showed that they comprised galactose, arabinose, xylose and glucose. The total phenol content of the RS, TA and CD-derived HAH concentrates were 37.53, 56.78 and 48.08mg GAE/g. The five lactic acid bacteria (LAB) isolates Q1B, Q2A, Q3B, G1C and G2B selected for prebiotic activity assays generated mixed responses with the highest growth in RS-HAH for Q2A and the least in TA-HAH for Q3B. Further, the isolates Q2A, Q3B, G1C, and G2B, which showed the highest growth performance, were identified through MALDI-TOF and 16S rRNA sequencing as Lactobacillus brevis. All the tested LAB isolates showed diauxic growth in crude HAH preparations to maximize the utilization of carbon resources for their proliferation. This suggests that the selected LAB isolates are efficient degraders of hemicellulosic sugars. This paves the way for the valorization of lignocellulosic biomass to produce prebiotic hemicellulosic autohydrolysate and consequently enhances environmental sustainability by improving resource efficiency.

Direct enzymatic hydrolysis of solid wheat straw with endo-xylanases: Effect of the temperature on the hemicellulose release and the product profile modulation

Prebiotics are non-digestible compounds that promote intestinal microbiota growth and/or activity. Xylooligosaccharides (XOS) are new prebiotics derived from the hemicellulose fraction of lignocellulosic materials. Challenges in using those materials as sources for prebiotic compounds lie in the hemicellulose extraction efficiency and the safety of those ingredients. In this sense, this work aims to optimize hemicellulose extraction and XOS production through direct enzymatic hydrolysis of alkali pre-treated wheat straw without undesired byproducts. By increasing the temperature of the enzymatic step from 40 °C to 65 °C we achieved an improvement in the extraction yield from 55 % to 80 %. Products with different degrees of polymerization were also noticed: while XOS ≤ X6 where the main products at 40 °C, a mixture of long arabinoxylan derived polymers (ADPo) and XOS ≤ X6 was obtained at 65 °C, irrespective of the extraction yield. Thus, a modulatory effect of temperature on the product profile is suggested here. Among the XOS ≤ X6 produced, X2-X3 were the main products, and X4 was the minor one. At the end of the hydrolysis, 146.7 mg XOS per gram of pre-treated wheat straw were obtained.

(Bio)electrochemical system: A systematic approach from agricultural waste to sewage wastewater treatment with nutrients and hydrogen recovery

Sustainable biowaste utilization is currently an interesting research area to enhance its conversion to value-added products. Electrochemical and bioelectrochemical technologies are cracking up the fractionization of various types of waste for environmental cleanup processes. In the present study, agricultural waste-based extracted material was used to capture the nutrients and/or pollutants from the anaerobic bioelectrochemically treated sewage wastewater (SWW). Hydrogen production potential of 15.52–11.77 times higher than the single carbon source indicated efficient utilization of organic and inorganic matters by extant microorganisms in the SWW. The electrochemical hemicellulose (HC) extraction, nutrient recovery and other components like applied potential (mV), NaOH (M) and rice straw load (%) analysis were evaluated at three factors and three levels. The N/C ratio of 0.06 and the highest functionalities in the 150-mV extracted HC, confirm its suitability to trap nutrients/pollutants from wastewater. With the potential to substitute expensive adsorbents in the future, the additional advantage of HCs being useful in the recovery of ammonium ions for use in agriculture could positively impact the global food security program. The aim of the study is not only the recovery of nutrients from waste but also to unravel the clean path of waste management with possible green energy production.

Hemicellulose‐Based Nanofibers Decorated In Situ with Silver Nanoparticles for Antibacterial Applications

AbstractThere is growing evidence that composites made up of nanomaterials and plant extracts are effective in combating drug‐resistant pathogens, which are increasing globally. In this study, a hemicellulose extract from cactus pads (Opuntia ficus indica) is blended with poly(vinyl) acetate and electrospun into fine nanofibers. Further, the electrospun nanofibers are encapsulated with silver nanoparticles (AgNPs), in situ, to form a nanocomposite, whose surface morphology are characterized using a scanning electron microscope (SEM). The SEM images showed smooth nanofiber strands (average diameter = 240 nm), with AgNPs randomly dispersed on them. The antibacterial activity of the nanocomposite is tested against five bacterial species. The results obtained showed that the nanonomposite has strong inhibitory effects against Gram‐positive and Gram‐negative bacteria, whereas the pristine nanofibers showed minimal or no antibacterial activity. This study demonstrates i) successful electrospinning of hemicellulose extracts into fine nanofibers and ii) encapsulation with AgNPs to produce a rigid nanocomposite with antimicrobial characteristics for various applications, especially those that require protection against pathogenic bacteria.

Metallic Wood through Deep-Cell-Wall Metallization: Synthesis and Applications.

Metallic wood combines the unique structural benefits of wood and the properties of metals and is thus promising for applications ranging from heat transfer to electromagnetic shielding to energy conversion. However, achieving metallic wood with full use of wood structural benefits such as anisotropy and multiscale porosity is challenging. A key reason is the limited mass transfer in bulk wood where fibers have closed ends. In this work, programmed removal of cell-wall components (delignification and hemicellulose extraction) was introduced to improve the accessibility of cell walls and mass diffusion in wood. Subsequent low-temperature electroless Cu plating resulted in a uniform continuous Cu coating on the cell wall, and, furthermore, Cu nanoparticles (NPs) insertion into the wood cell wall. A novel Cu NPs-embedded multilayered cell-wall structure was created. The unique structure benefits compressible metal-composite foam, appealing for stress sensors, where the multilayered cell wall contributes to the compressibility and stability. The technology developed for wood metallization here could be transferred to other functionalizations aimed at reaching fine structure in bulk wood.

Application of Proton Ionic Liquid in the Process of Obtaining Bioethanol from Hemp Stalks

In this work, hemp (Cannabis sativa L.) stalks were pretreated with pyrrolidinium acetate [Pyrr][AC] to increase the availability of cellulose for cellulolytic enzymes and thus improve the production of 2G ethanol from reducing sugars. The process was carried out under different temperature and time conditions: The control sample was raw material and deionized water, and the second sample was kept at 21 °C for 24 h. The third sample was kept at 90 °C for 30 min, and the fourth sample was kept at the same temperature for 24 h. For each pretreatment, the extraction of lignin and hemicellulose was determined, as well as the change in biomass composition before and after pretreatment. The stalks of hemp seed contained 41.54% cellulose, 18.08% lignin and 28. 87% hemicellulose. [Pyrr][AC] used to dissolve seed hemp at 90 °C for 24 h was most effective in the extraction of this biopolymer, extracting 3.1% content. After enzymatic hydrolysis, the highest content of reducing sugars was found for samples of hemp stalks that were first pretreated with proton ionic liquid (PIL) and stirred at 90 °C for 24 h. On the other hand, the highest ethanol content (5.6 g/L) after fermentation and yeast viability (56.7%) after 72 h were obtained in samples pretreated at 90 °C and for 24 h.

Alkaline wet oxidative pretreatment and acid hydrolysis of wheat straw for squalene and monomethyl branched chain fatty acids rich lipid production in Lentibacillus salarius BPIITR

Lignocellulosic biomass has high potential for use as a carbon substrate in microbial fermentation. However, the generation of various lignin-derived phenolic compounds, benzoic acids, and carbohydrate-derived furan aldehydes poses a major bottleneck. In this study, wheat straw was subjected to sequential alkaline wet oxidative pretreatment (AWOP) and acid hydrolysis to extract hemicellulose sugars. After statistical optimization, 251.50 mg/g total sugar (228.57 mg/g pentose, 22.93 mg/g hexose) and 19.64 mg/g hydrolysis by-products were achieved, with a theoretical pentose recovery of 89.57% and residual cellulose of 72.1%. The lignin-rich and carbohydrate-rich liquids from the AWOP treatment and acid hydrolysis, respectively, were valorised to produce squalene and branched chain fatty acid rich lipid using Lentibacillus salarius BPIITR. The lipid of 100.9 ± 3.53 and 235.75 ± 10.39 mg/g of dcw rich in squalene up to 3121.17 ± 25.49 and 676.41 ± 134.27 μg/g of lipid was produced in AWOP and acid hydrolysate, respectively. In the AWOP hydrolysate, lignin content was reduced by 63.78%, compared to a 40.18% reduction in the acid hydrolysate. GC-MS analysis of the lignin monomer and metabolites suggests the potential influence of lignin monomers on the biosynthetic pathway of squalene and carbohydrate content on the branched chain fatty acids accumulation in the halophilic bacterial lipid of L. salarius BPIITR.

Extraction and characterization of hemicellulose and lignin contents of areca fiber

Extraction and characterization of hemicellulose and lignin contents of areca fiber

Energy Optimization from raw materials and evaluate hemicelluloses. García.M.T*. García, J.C., Loaiza, J.M., Blanco, J., López, F.

The aim of this study was to optimize the energetic use and extraction of hemicelluloses by hydrolysis with dilute acid of three different lignocellulosics materials from rapid growth biomass using a factorial experimental design and multiple regression models. For that, calorific power value and chemical composition of solid phases after acid hydrolysis of three different lignocellulosic materials were determined (Chamaecytisus proliferus or tagasaste-, Leucaena leucocephala, and a dihybrid of Paulownia (fortunei and elongata). These solid phases were assessed for obtainment of energy, sugars and other by product. Superior calorific value at constant volume over dry basis and lower calorific value at constant pressure was determinated for energy purposes. The proposed acid hydrolysis process allows increased yield and xylan under more selective extraction conditions. Also higher values of superior calorifc power values that raw materials are reported. The operational ranges are especially suitable for the extraction of xylose, which was virtually quantitative at 170 ºC The selective extraction of hemicelulloses alows to have a solid part with a high content in glucan a lignin and the value of superior calorimetric is suitable for obtain energy.

Lignin carbon-initiated Ni/K/Mo2C catalyst for efficient synthesis of higher alcohols from syngas

Bamboo lignin, the principal constituent of non-wood pulping black liquor, is ecologically and environmentally harmful due to its complex molecular structure and stability. Additionally, the syngas-based synthesis of higher alcohols is a desired industrial application, alleviating the dependency on petroleum resources. However, developing highly efficient catalysts with high space–time yield and selectivity towards higher alcohols remains challenging. Herein, for the first time, taking into account the permeable structure of bamboo lignin in paper-making black liquid resulting from cellulose and hemicellulose extraction, porous nano molybdenum carbide was manufactured by designed pretreatment and activation processes of the lignin, which was further doped by the K and Ni additive to create a highly efficient catalyst (Ni/K/Mo2C@LC) for the high alcohols synthesis reaction, yielding a surprising space–time yield of 0.455 g/gcat/h) to alcohol products under the optimal reaction conditions. Control experiments and characterizations were conducted over relevant catalysts, revealing that Ni and K could be integrated to regulate the adsorption property, acidity/basicity, and carbon chain growth ability of the catalysts. Also, the open mesoporous lignin carbon provided larger metal particles, enhancing the hydrogenation ability and better balancing the non-dissociative and dissociative active sites for the high alcohol synthesis reaction. These results provide insights into the structure design of carbide catalysts toward efficiently utilizing industrial lignin and other biomass-derived feedstocks, and the development of an efficient Mo-based catalyst for syngas conversion.

Optimization of microwave-expanding pretreatment and microwave-assisted extraction of hemicellulose from bagasse cells with the exploration of the extracting mechanism

Hemicellulose is mainly distributed in the tightly packed S2 layer of the plant cell wall and the middle lamella. This rigid microstructure of wood and interactions among hemicellulose, lignin, and cellulose jointly restrict the separation and transformation of hemicellulose in the wood matrix. To address this issue, a method combined with microwave-expanding pretreatment (MEP) and microwave-assisted extraction (MAE) with a NaOH solution was carried out. We found that the MEP could effectively create new pathways for bagasse cells in mass transferring. More specifically, 195 % of the specific surface area (m2/g) with 193 % of the pores (>50 nm) increased after MEP; the SEM images also confirmed that the microstructure of bagasse was modified. MAE could considerably exfoliate hemicellulose from cellulose fiber and accelerate mass transfer. Additionally, we optimized MEP and MAE by using response surface methodology (RSM). The optimal parameters were 370 K, 3.7 min, 1081 W microwave power, and 9.9 wt% NH4HCO3 consumption for the MEP and 1100 W microwave power, 2.5 wt% NaOH concentration, 34.6 min reaction time for MAE, respectively. Moreover, molecular dynamics (MD) simulation suggests that NaOH could significantly lower the work needed to peel off the xylan chain from cellulose nanofibril.

Highly selective extraction of lignin and hemicellulose with retained original structure from sugarcane bagasse via low-temperature soaking and acidic precipitation

Low-temperature soaking can be used to extract the majority of the hemicellulose and lignin from bagasse without substantially changing its structure.The effects of temperature, alkali concentration, and treatment duration on the extraction of hemicellulose and lignin from bagasse via low-temperature alkaline soaking were investigated. Acid precipitation provided a solution by separating lignin from black liquor and enabled the categorization of the lignin into different groups based on the reduced pH of the solution. The precipitation of hemicellulose and lignin from black liquor under different pH conditions was investigated. The optimal pretreatment conditions for bagasse were determined to be an alkali concentration of 75 g L–1 at 35 °C for 8 d, achieving a pentose selectivity of 0.97. The main organic components of lignin and carbohydrates precipitated in different pH environments. The highest xylose content in the precipitate was obtained at pH 13.65 (above 85%), whereas the lignin content was above 90% at pH 2. The results of fourier transform infrared (FTIR) spectroscopy and two-dimensional nuclear magnetic resonance (2D NMR) analyses showed that the structure of the water-soluble substances and precipitates slightly changed during alkali pretreatment, which allowed for increased accessibility in subsequent biorefineries, such as in catalytic hydrogenolysis.

Ultrasound-Assisted Cold Alkaline Extraction: Increasing Hemicellulose Extraction and Energy Production from Populus Wood

Alkaline pretreatments are considered highly effective for the separation of the different components of lignocellulosic biomass. However, cold alkaline extraction (CAE) exhibits minimal modification/degradation of hemicellulosic fraction and successfully accomplishes efficient delignification. In this research, the fast-growing clone AF2 of Populus x euramericana wood was utilized as the raw material and subjected to ultrasound-assisted CAE. The objective of incorporating ultrasound into cold alkaline extraction is to increase the yield of a hemicellulosic-rich liquid phase that can be used to produce high-value products such as furfural or xylitol. Simultaneously, it aims to obtain a solid phase with a higher calorific value compared to the raw material. The results, obtained from a central composite factorial design, demonstrated that the CAE process for 90 min at a sodium hydroxide concentration of 100 g L−1, a temperature of 30 °C, and with ultrasound assistance maximized hemicellulose extraction in the liquid phase (60.8% was extracted) and improved the heating value of solid phase.

Integrated Hemicellulose Extraction and Papermaking Fiber Production from Agro-Waste Biomass.

The present study deals with the valorization of corn stalks in an integrated processing strategy targeting two products: extracted hemicelluloses (HC) and papermaking fibers. Preliminary trials were conducted to assess the individual or the combined effects of biomass treatment on the quality of the obtained hemicelluloses and papermaking fibers. Depending on the hot alkaline extraction (HAE) conditions, the extracted HC had a xylan content between 44-63%. The xylan removal yield ranged between 19-35%. The recovery of HC from the extraction liquor and final black liquor was significantly affected by process conditions. The experimental approach continued with the study of HAE conditions on the obtained paper's mechanical properties. The optimization approach considered conserving paper strength properties while achieving an equilibrium with the highest possible HC extraction yield. The optimal values are sodium hydroxide concentration (1%), process time (33 min), and temperature (100 °C). The xylan content in the separated HC sample was ~55%. An extended extraction of HC from the resulting pulp under hot alkaline conditions with 5% NaOH was performed to prove the HC influence on paper strength. The xylan content in HC samples was 65%. The consequence of xylan content reduction in pulp leads to 30-50% mechanical strength loss.