Physico-chemical and structural characterization of hemicelluloses from wheat straw by alkaline peroxide extraction

Hemicellulose and unlocking potential for sustainable applications in biomedical, packaging, and material sciences: A narrative review

Hemicellulose, a complex polysaccharide abundantly found in plant cell walls, has garnered significant attention for its versatile applications in various fields including biomedical, food packaging, environmental, and material sciences. This review systematically explores the composition, extraction methods, and diverse applications of hemicellulose-derived materials. Various extraction techniques such as organic acid, organic base, enzyme-assisted, and hydrothermal methods are discussed in detail, highlighting their efficacy and potential drawbacks. The applications of hemicellulose encompass biodegradable films, edible coatings, advanced hydrogels, and emulsion stabilizers, each offering unique properties suitable for different industrial needs. Current challenges in hemicellulose research include extraction efficiency, scalability of production processes, and optimization of material properties. Opportunities for future research are outlined, emphasizing the exploration of new applications and interdisciplinary approaches to harness the full potential of hemicellulose. This comprehensive review aims to provide valuable insights for researchers and industry professionals interested in utilizing hemicellulose as a sustainable and functional biomaterial.

From Field to Pharmacy: Isolation, Characterization and Tableting Behaviour of Microcrystalline Cellulose from Wheat and Corn Harvest Residues

A lack of strategies for the utilization of harvest residues (HRs) has led to serious environmental problems due to an accumulation of these residues or their burning in the field. In this study, wheat and corn HRs were used as feedstock for the production of microcrystalline cellulose (MCC) by treatment with 2-8% sodium hydroxide, 10% hydrogen peroxide and further hydrolysis with 1-2 M hydrochloric acid. The changes in the FT-IR spectra and PXRD diffractograms after chemical treatment confirmed the removal of most of the lignin, hemicellulose and amorphous fraction of cellulose. A higher degree of crystallinity was observed for MCC obtained from corn HRs, which was attributed to a more efficient removal of lignin and hemicellulose by a higher sodium hydroxide concentration, which facilitates the dissolution of amorphous cellulose during acid hydrolysis. MCC obtained from HRs exhibited lower bulk density and poorer flow properties but similar or better tableting properties compared to commercial MCC (CeolusTM PH101). The lower ejection and detachment stress suggests that MCC isolated from HRs requires less lubricant compared to commercial MCC. This study showed that MCC isolated from wheat and corn HRs exhibits comparable tableting behaviour like commercial sample, further supporting this type of agricultural waste utilization.

Ultra-sensitive detection and scavenging of arsenic ions and ciprofloxacin using 3D multipurpose hemicellulose based aerogel: Adsorption mechanism and RSM optimization

Trace level detection and efficient removal of arsenite ions (As (III)) and ciprofloxacin (CPR) antibiotic was achieved using hemicellulose based ratiometric fluorescent aerogel. Hemicellulose derived from rice straw was oxidised to dialdehyde hemicellulose followed by crosslinking using chitosan via a Schiff base reaction (C = N) yielding a highly porous 3D fluorescent aerogel (CS@DAHCA). Various factors governing adsorption were analyzed by applying response surface methodology (RSM) approach. CS@DAHCA exhibited ultra-trace level monitoring with the limit of detection of 3.529 pM and 55.2 nM for As (III) and CPR, respectively. The CS@DAHCA showed maximum adsorption capacity of 185 μg g-1 and 454 mg g-1 for As (III) and CPR, respectively. Finally, the feasibility of CS@DAHCA was ascertained for real water samples confirming it as promising candidate for remediation of As (III) and CPR.

Isolation and characterization of nanocellulose from selected hardwoods, viz., Eucalyptus tereticornis Sm. and Casuarina equisetifolia L., by steam explosion method

Extraction of nanocellulose is challenging, especially from hardwoods due to its complex chemical structure as well as structural hierarchy. In this study, nanocellulose was isolated from wood pulp of two hardwood species, namely Eucalyptus tereticornis Sm. and Casuarina equisetifolia L. by steam explosion process. Pure cellulose wood pulp was obtained through Kraft pulping process followed by alkaline and bleaching pre-treatments. Isolated nanocellulose was characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM), Fourier Transformed Infrared (FTIR) Spectra, Thermogravimetric Analysis (TGA), and X-ray diffraction (XRD) studies. Nanocellulose obtained from both species showed non-significant difference with average diameter of 27.801 nm for eucalyptus and 28.690 nm for casuarina, which was confirmed from TEM and AFM images. FTIR spectra of nanocellulose showed prominent peaks corresponding to cellulose and absence of peaks corresponding to lignin. The elemental purity of nanocellulose was confirmed with EDAX detector. XRD analysis showed the enrichment of crystalline cellulose in nanocellulose, and also confirmed the significant conversion of cellulose I to cellulose II. During TG analysis the untreated fibres started to degrade earlier than the nanocellulose which indicated the higher thermal stability of nanocellulose. Highly entangled network like structure along with high aspect ratio make the nanofibres a versatile material for reinforcing the composites. This successful method can be replicated for industrial level production of cellulose nanofibres.

Advances in extraction, purification, structural characteristics and biological activities of hemicelluloses: A review

Hemicelluloses, a major component of plant cell walls, are a non-cellulosic heteropolysaccharide composed of several distinct sugars that is second in abundance to cellulose, which are one of the most abundant and cheapest renewable resources on earth. Hemicelluloses structure is complex and its chemical structure varies greatly among the different plant species. In addition to its wide use in production of feed and other chemical materials, hemicelluloses are known for its remarkable biological activities that remain largely underutilised to date. Therefore, comprehensive investigations of hemicelluloses structural and biological properties would be helpful for achieving rational utilisation and high-value conversion of this underutilised substance into agents with enhanced health benefits for incorporation in drugs and health foods. In this review, details of diverse research initiatives that have enhanced our understanding of hemicelluloses properties are summarised, including hemicelluloses sources, extraction and purification methods, structural characteristics and biological activities. Furthermore, hemicelluloses structure-activity relationships and new directions for future hemicelluloses research studies are discussed.

Thermal and Physico-Chemical Characteristics of Plaster Reinforced with Wheat Straw for Use as Insulating Materials in Building

In this paper, a new material consisting of plaster and wheat straw was studied with the purpose of reducing energy consumption. The aim of this study is to test this new compound for use as an insulation material in buildings, where the samples were prepared by mixing wheat straw after grinding it in different proportions from 0% to 15%. On the other hand, the physico-chemical properties and thermal conductivity of the samples were experimentally investigated, and the time lag and energy savings for the samples were also studied. The results showed that the addition of wheat straw leads to an increase in the time lag and also to a decrease in the thermal conductivity, which leads to an improvement in the thermal resistance and energy savings. As well, fiber addition has no effect on the chemical composition of the matrix, as shown by FTIR and XRD analyses.The findings of the DSC and TGA analysis indicate that the inclusion of wheat straw fibers has an effect on the thermal characteristics of the matrix. This new biocomposite can be used as an additive to plaster to create environmentally friendly composite materials for thermal insulation in buildings.

An Experimental Study on the Hot Alkali Extraction of Xylan-Based Hemicelluloses from Wheat Straw and Corn Stalks and Optimization Methods

In this paper, we describe an experimental study on the hot alkali extraction of hemicelluloses from wheat straw and corn stalks, two of the most common lignocellulosic biomass constituents in Romania. The chemical compositions of the raw materials were determined analytically, and the relevant chemical components were cellulose, hemicelluloses, lignin, and ash. Using the response surface methodology, the optimum values of the hot alkaline extraction parameters, i.e., time, temperature, and NaOH concentration, were identified and experimentally validated. The physicochemical characterization of the isolated hemicelluloses was performed using HPLC, FTIR, TG, DTG, and 1H-NMR spectroscopy. The main hemicellulose components identified experimentally were xylan, arabinan, and glucan. The study emphasizes that both corn stalks and wheat straw are suitable as raw materials for hemicellulose extraction, highlighting the advantages of alkaline pretreatments and showing that optimization methods can further improve the process efficiency.

Oxidative Condensation of Furfural with Ethanol Using Pd-Based Catalysts: Influence of the Support

PdO nanoparticles were deposited on several supports (β-zeolite, Al2O3, Fe2O3, MgO, and SiO2), which displayed different crystallinity, textural properties, and amount of acid and basic sites. These catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption–desorption isotherms at −196 °C, NH3 and CO2 thermoprogrammed desorption analyses (NH3- and CO2-TPD, and X-ray photoelectron spectroscopy (XPS). Pd-based catalysts were tested in the oxidative condensation of furfural with ethanol to obtain value-added chemicals. The catalytic results revealed high conversion values, although the presence of a high proportion of carbonaceous deposits, mainly in the case of the PdO supported on β-zeolite and Al2O3, is also noteworthy. The presence of basic sites led to a beneficial effect on the catalytic behavior, since the formation of carbonaceous deposits was minimized. Thus, the 2Pd-MgO (2 wt.% Pd) catalyst reached the highest yield of furan-2-acrolein (70%) after 3 h of reaction at 170 °C. This better catalytic performance can be explained by the high basicity of MgO, used as support, together with the large amount of available PdO, as inferred from XPS.

Effects of surface modification on heavy metal adsorption performance and stability of peanut shell and its extracts of cellulose, lignin, and hemicellulose

Effects of surface modification by carboxyl group on Pb²⁺ adsorption performances and stability of peanut shell and its extracts (cellulose, lignin, and hemicellulose) were investigated. Stability of the biosorbents was measured by determining organic compound release amount (TOC). Results showed that adsorption capacity of peanut shell and the extract was poor and stability of them was not good enough. Amount of organic compound released from the unmodified sorbents followed the order: cellulose > lignin > peanut shell > hemicellulose. Hemicellulose was the main organic compound release resource for the raw peanut shell. Due to the poor stability of the raw materials, peanut and its extract could not be used directly in the practical waste water treatment. After modification, adsorption capacity of peanut shell, cellulose, lignin, and hemicellulose increased by 4- to 6-folds. Stability of the modified sorbents also increased significantly, and TOC determined for the modified peanut shell, cellulose, and hemicellulose was lower than 4.0 mg L^-1 in the optimum pH range from 4.0 to 6.0 even using for 30 days, which was lower than the drinking water standard in China. Modified peanut shell and its extract except for lignin could be used safely in pH ranged from 4.0 to 6.0. Surface modification could improve the adsorption performances and stability of the biosorbents.

Dilute acid hydrolysis of spoiled wheat grains: Analysis of chemical, rheological and spectral characteristics

In this work, hydrolysis of spoiled wheat grains using dilute acid (5, 10%; 1 N HCl) was investigated and the effect of hydrolysis conditions on reducing sugars, soluble proteins, rheology and infrared spectra of the hydrolysates was determined. Hydrolysis with 10% acid concentration released more quantities of reducing sugar (16.47 mg/mL) at shorter hydrolysis times whereas 5% acid concentration produced higher protein content (28.74 mg/mL) for similar durations. Flow characteristics demonstrated an increased apparent viscosity of the hydrolysates retrieved after 4.5 h of hydrolysis possibly due to breakdown of hemicelluloses and lignin into sugars. Infrared spectroscopy showed release of carbonates after 1.5 h and 5.5 h of hydrolysis perhaps due to oxidation of lignin or a reaction between acid and sugars. The study highlights that acid hydrolysis would be a rapid and cost effective approach to produce fermentable hydrolysates for bio-processing industry applications while generating an avenue for waste grain utilization.

Enhancement of Hydrotropic Fractionation of Poplar Wood using Autohydrolysis and Disk Refining Pretreatment: Morphology and Overall Chemical Characterization

Solid acids have been proposed as a hydrolytic agent for wood biomass dissolution. In this work, we presented an environmentally friendly physicochemical treatment to leave behind cellulose, dissolve hemicellulose, and remove lignin from poplar wood. Several pretreatments, such as autohydrolysis and disk refining, were compared to optimize and modify the process. The p-toluenesulfonic acid could extract lignin from wood with a small amount of cellulose degradation. Disk refining with subsequent acid hydrolysis (so-called physicochemical treatment) doubled the delignification efficiency. A comprehensive morphology and overall chemical composition were provided. The crystallinity index (CrI) of treated poplar was increased and the chemical structure was changed after physicochemical treatment. Optical microscopy and scanning electron microscopy analysis demonstrated physicochemical treatment affected the morphology of poplar wood by removing lignin and generating fiberization. In general, this work demonstrated this physicochemical method could be a promising fractionation technology for lignocellulosic biomass due to its advantages, such as good selectivity, in removing lignin while preserving cellulose.

A Comparative Study on the Characterization of Nanofibers with Cellulose I, I/II, and II Polymorphs from Wood

Polymorphic changes in cellulose nanofibers (CNFs) are closely related to their properties and applications, and it is of interest to investigate how polymorphic changes influence their properties. A comparative study on the properties of CNFs with cellulose I, I/II, and II polymorphs from wood was conducted herein. CNFs were obtained by chemical extraction combined with a simple and efficient mechanical treatment (one pass through a grinder). This process resulted in a relatively high yield of 80⁻85% after a simple grinding treatment. The polymorphic changes in the CNFs and the chemical composition, morphology, tensile performances, and thermal properties were systematically characterized and compared. The X-ray diffraction and FTIR analyses verified the existence of three types of purified pulps and CNFs with cellulose I, cellulose I/II, and cellulose II polymorphs (CNF-I, CNF-I/II, CNF-II). Morphological observations presented that these three types of CNFs all exhibited high aspect ratios and entangled structures. Tensile testing showed that the CNF films all exhibited high tensile strengths, and the fracture strains of the CNF-I/II (11.8%) and CNF-II (13.0%) films were noticeably increased compared to those of the CNF-I film (6.0%). If CNF-II is used as reinforcing material, its larger fracture strain can improve the mechanical performance of the CNF composites, such as fracture toughness and impact strength. In addition, CNF-I, CNF-I/II, and CNF-II films showed very low thermal expansion in the range 20⁻150 °C, with the coefficient of thermal expansion values of 9.4, 17.1, and 17.3 ppm/K, respectively. Thermogravimetric analysis (TGA) revealed that the degradation temperature of CNF-I and CNF-II was greater than that of CNF-I/II, which was likely due to increased α-cellulose content. This comparative study of the characterization of CNF-I, CNF-I/II, and CNF-II provides a theoretical basis for the application of CNFs with different polymorphs and could broaden the applications of CNFs.

A microwave-assisted aqueous ionic liquid pretreatment to enhance enzymatic hydrolysis of Eucalyptus and its mechanism

A novel pretreatment strategy based on combination of microwave and ionic liquid [TBA][OH] was developed for enhancing enzymatic hydrolysis of Eucalyptus sawdust. The sugar yield of pretreated sample achieved 410.67 mg/g in 48 h, which suffered from optimized microwave-assisted [TBA][OH] pretreatment. The work mechanism was illuminated by chemical composition, Fourier transform infrared spectroscopy (FTIR), ¹³C cross polarization/magic-angle spinning solid state NMR (¹³C solid NMR), X-ray diffraction (XRD) and scanning electron microscope (SEM) analyses. The combined effect of microwave and [TBA][OH] leads to the violent deconstruction of lignin, removal of hemicelluloses, destruction of crystalline region and an eroded, pored and irregular micro-morphology. As a green, relatively inexpensive and high efficient pretreatment, microwave-assisted [TBA][OH] pretreatment has great potential in the field of bio-refinery.

Fates of hemicellulose, lignin and cellulose in concentrated phosphoric acid with hydrogen peroxide (PHP) pretreatment

Xylan, de-alkaline lignin and microcrystalline cellulose were employed as representative models of hemicellulose, lignin and cellulose in lignocellulosic biomass. These three model compounds, together with the real-world biomass, wheat straw were pretreated using the newly developed PHP pretreatment (concentrated phosphoric acid plus hydrogen peroxide) to better understand the structural changes of the recovered solid and chemical fractions in the liquid. Results showed that almost all xylan and higher than 70% lignin were removed from wheat straw, and more than 90% cellulose was recovered in the solid fraction. The pretreated model xylan recovered via ethanol-precipitation still maintained its original structural features. The degree of polymerization of soluble xylooligosaccharides in liquid was reduced, resulting in the increase of monomeric xylose release. Further xylose oxidization via the path of 2-furancarboxylic acid → 2(5H)-furanone → acrylic acid → formic acid was mainly responsible for xylan degradation. The chemical structure of de-alkaline lignin was altered significantly by PHP pretreatment. Basic guaiacyl units of lignin were depolymerized, and aromatic rings and side aliphatic chains were partially decomposed. Ring-opening reactions of the aromatics and cleavage of C–O–C linkages were two crucial paths to lignin oxidative degradation. In contrast to lignin, no apparent changes occurred on microcrystalline cellulose. The reason was likely that acid-depolymerization and oxidative degradation of cellulose were greatly prevented by the formed cellulose phosphate.

The transformation of cellulose, hemicellulose, and lignin in lignocellulosic biomass in a novel pretreatment are elucidated based on model fractions.

G-lignin and hemicellulosic monosaccharides distinctively affect biomass digestibility in rapeseed

In this study, total 19 straw samples from four Brassica species were determined with a diverse cell wall composition and varied biomass enzymatic digestibility under sulfuric acid or lime pretreatment. Correlation analysis was then performed to detect effects of cell wall compositions and wall polymer features (cellulose crystallinity, hemicellulosic monosaccharides and lignin monomers) on rapeseeds biomass digestibility. As a result, coniferyl alcohol (G-lignin) showed a strongly negative effect on biomass saccharification, whereas hemicellulosic monosaccharides (fucose, galactose, arabinose and rhamnose) were positive factors on lignocellulose digestions. Notably, chemical analyses of four typical pairs of samples indicated that hemicellulosic monosaccharides and G-lignin may coordinately influence biomass digestibility in rapeseeds. In addition, Brassica napus with lower lignin content exhibited more efficiency on both biomass enzymatic saccharification and ethanol production, compared with Brassica junjea. Hence, this study has at first time provided a genetic strategy on cell wall modification towards bioenergy rapeseed breeding.

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.

PCL/PVA nanoencapsulated reinforcing fillers of steam exploded/autoclaved cellulose nanofibrils for tissue engineering applications

The process of extraction of cellulose nanofibrils by steam explosion followed by electrospinning with biodegradable polymers to yield PCL/PVA nanoencapsulated cellulosic reinforcing fillers for tissue engineering applications.

Isolation and Characterization of Corncob Cellulose Fibers using Microwave-Assisted Chemical Treatments

Cellulose fibers were obtained from corncob by using microwave-assisted chemical treatments (microwave-assisted alkaline pretreatment and microwave-assisted bleaching). These treatments efficiently removed the hemicellulose and lignin from the original corncob and increased the cellulose fiber content. The morphology, chemical structure, degree of crystallinity and thermal degradation characteristics of the resultant cellulose fibers were studied by using field emission scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and thermogravimetric analysis. These microwave-assisted chemical treatments decreased the diameter of the cellulose fibers from 25–125 µm to 10–20 µm. The crystallinity of the corncob cellulose fibers increased from 32.7% to 73% due to the chemical treatments. The degradation temperature of the cellulose fibers was >260°C. The cellulose fibers obtained from these treatments can be used as biocomposites in reinforced polymer manufacturing.

Microscopic structure and properties changes of cassava stillage residue pretreated by mechanical activation

This study has focused on the pretreatment of cassava stillage residue (CSR) by mechanical activation (MA) using a self-designed stirring ball mill. The changes in surface morphology, functional groups and crystalline structure of pretreated CSR were examined by using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) under reasonable conditions. The results showed that MA could significantly damage the crystal structure of CSR, resulting in the variation of surface morphology, the increase of amorphous region ratio and hydrogen bond energy, and the decrease in crystallinity and crystalline size. But no new functional groups generated during milling, and the crystal type of cellulose in CSR still belonged to cellulose I after MA.

Pretreatment and enzymatic hydrolysis of wheat straw (Triticum aestivum L.)--the impact of lignin relocation and plant tissues on enzymatic accessibility

Wheat straw is a potential feedstock for bioethanol production. This paper investigates tissues from whole internode sections subjected to hydrothermal pretreatment at 185°C and subsequent enzymatic hydrolysis up to 144 h. Analyses revealed an increase in surface lignin as hydrolysis progressed, which could be coupled to the gradual decrease in hydrolysis rate over time. The data support the hypothesis of lignin extraction from the cell wall matrix during pretreatment and deposition as droplets upon cooling. These droplets are assumed to accumulate during enzymatic hydrolysis. Additionally, after 144 h of enzymatic hydrolysis the cortex had vanished, exposing the heavier lignified vascular tissue. Accumulation of lignin droplets and exposure of residual lignin could be part of the explanation for the decreasing hydrolysis rate. Flattening of macrofibrils after pretreatment together with more indentations on the surfaces was also observed, possibly caused by a proposed synergistic effect of cellobiohydrolases and endoglucanases.