Search Results (130)

Cellulose crystallinity is frequently associated with lignocellulosic biomass digestibility, yet its development during multistep biorefinery processing and its relationship with enzymatic hydrolysis remain difficult to isolate. This study investigated the evolution of cellulose crystallinity in wheat straw (Triticum aestivum) during Hot-Water Pretreatment (HWP), Water Pretreatment (WP), Organosolv extraction, sequential washing, and drying, and related these changes to enzymatic glucose yield. Crystallinity was determined using X-ray diffraction and an ATR-FTIR-based PLS model, while enzymatic hydrolysis was evaluated by HPLC-based glucose quantification. HWP caused a temperature-dependent decrease in crystallinity from 47.5 ± 1.3% in untreated straw to 27.0 ± 2.2% at 120 °C, whereas WP at room temperature caused no significant change. However, without subsequent Organosolv extraction, both pretreatments alone resulted in low glucose yields of approximately 10%, indicating that cellulose crystallinity is only one of several factors governing enzymatic hydrolysis efficiency. During washing after Organosolv extraction, crystallinity increased from 40.6 ± 2.1% to 54.2 ± 1.3%, whereas, under the tested conditions, glucose yield was more closely associated with the estimated residual ethanol concentration than with the change in crystallinity. Drying had the strongest effect, increasing crystallinity by up to 53.6% relative to the wet state. Overall, cellulose crystallinity should be considered as one of several interacting factors governing enzymatic digestibility, and sample moisture history must be carefully controlled when comparing crystallinity data. Full article

Grape stems (GSs), a key by-product of winemaking, are a rich source of bioactive polyphenols and have potential applications in functional foods, antioxidant additives, and cosmetics. In this study, the production of polyphenol-rich extracts from GS using an ultrasound-assisted, acid-catalyzed organosolv process was explored, using isopropanol as solvent. Sulfuric acid served as an effective catalyst for breaking down lignocellulosic material, and the process conditions were optimized using response surface methodology to maximize efficiency. Following an initial single-factor analysis, sulfuric acid and isopropanol concentrations were selected as the main variables. The optimal conditions—54% isopropanol and 1% sulfuric acid—yielded the highest polyphenol content (50.9 ± 4.4 mg caffeic acid equivalents per gram of dry mass). Further analysis using liquid chromatography–mass spectrometry revealed that acid catalysis significantly altered the polyphenolic composition of the extracts. These changes enhanced antioxidant potency, as expressed by the radical scavenging activity but not by the reducing power, while the exact nature of the newly formed compounds was unclear. Overall, the results provide useful insights into modifying the polyphenolic profile of grape stems to obtain extracts with improved antioxidant capacity, supporting more sustainable and value-added uses of winemaking by-products within biorefinery systems. Full article

Agricultural residues represent an abundant renewable resource for sustainable lignocellulosic biorefineries, offering opportunities to produce value-added biopolymers while mitigating the environmental impacts associated with conventional disposal. This study evaluated the technical feasibility of using sorghum stubble as a feedstock for the recovery of cellulose, hemicellulose, and lignin through an ethanol–water organosolv process. Specifically, the study aimed to separate the main structural polymers of sorghum stubble and evaluate the performance of the proposed fractionation system. The biomass was treated at 180 °C and approximately 30 bar, followed by chlorine-free peroxide bleaching. The hemicellulose fraction was obtained by extracting the holocellulose (Wise method) and precipitating the dissolved hemicellulose using a 3:1 (v/v) ethanol-to-liquor ratio. The lignin fraction was isolated from the black liquor through vacuum distillation and drying. This approach yielded a cellulose fraction (23.66 wt%), a hemicellulose fraction (36.22 wt%), and a lignin fraction (30.35 wt%), corresponding to an overall polymer recovery of approximately 90 wt%. Structural and physicochemical characterization (FTIR, SEM, XRD, and TGA) supported the fractionation of the lignocellulosic matrix and identified characteristic structural and physicochemical features of the recovered cellulose, hemicellulose, and lignin fractions. SEM revealed substantial structural breakdown following the organosolv treatment, while TGA demonstrated distinct degradation behaviors among the components. Notably, the crystallinity index increased from 38% in the raw material to 71% in the cellulose fraction, indicating effective removal of amorphous components. A preliminary mass–energy analysis showed that approximately 96% of the initial energetic content of the biomass was retained in the polymers. Furthermore, approximately 70% of the ethanol used was recycled, highlighting the potential for solvent reintegration under the evaluated laboratory conditions. Overall, these findings demonstrate the potential of sorghum stubble as a renewable feedstock for the recovery of lignocellulosic polymers and provide a technical basis for the future optimization of organosolv-based biorefineries. Full article

Growing demand for more sustainable packaging has increased interest in bio-based adhesives as alternatives to conventional fossil-derived systems. Among renewable raw materials, lignin is particularly attractive because of its aromatic structure, phenolic functionality, and availability as a side stream of pulp, paper, and biorefinery processes. This review critically examines the potential of lignin-based adhesives for packaging applications. Selected polysaccharide-, protein-, vegetable-oil-, and tannin-based systems are briefly discussed as comparative references, while the main focus is placed on the properties of kraft lignin, lignosulfonates, organosolv lignin, and soda lignin. Their structural differences, adhesive behaviour, and suitability for chemical modification through hydroxymethylation, phenolation, demethylation, depolymerization, oxidation, and epoxidation are evaluated. Because most lignin-adhesive research concerns wood bonding, the transferability of these findings to paper, paperboard, labels, coatings, films, and hot-melt packaging adhesives is critically assessed. Direct evidence for packaging applications remains limited, although existing studies demonstrate promising opportunities for paper bonding, pressure-sensitive systems, and paperboard hot-melt adhesives. Key challenges include lignin heterogeneity, processing complexity, moisture resistance, colour, food-contact safety, scalability, and compatibility with recycling. Full article

The extensive use of synthetic polymers has raised significant environmental concerns due to their non-biodegradable nature and persistence in the environment. Cellulose-based materials have attracted considerable interest owing to their excellent inherent properties which enable their wide range of industrial and biomedical applications. In this study, an integrated approach (hydrothermal process, organosolv delignification and chlorine-free bleaching) was evaluated to obtain high-purity cellulose fiber from sugarcane bagasse (SCB). The untreated SCB was first subjected to hydrothermal process under varying experimental conditions defined by a central composite design (170–190 °C, 30–50 min) using a solid-to-liquid ratio of 1:10 (w/v). The hydrothermally pretreated solid was subsequently delignified using an organosolv process with an aqueous solution of 40% (v/v) ethanol and 0.1% (w/v) NaOH at 180 °C for 20 min. Finally, the organosolv delignified SCB was bleached with 1% (v/v) H₂O₂ and 1% NaOH (w/v) at 80 °C for 1 h. The bleached cellulose fiber exhibited a composition of 97.79 ± 0.19% cellulose, 1.10 ± 0.14% lignin and 0.23 ± 0.13% hemicellulose. XRD analysis displayed a notable increase in the crystallinity index from 52.2% in untreated SCB to 70.7% in the bleached cellulose fibers (BCF). Furthermore, FTIR revealed the disappearance of characteristic lignin and hemicellulose peaks at 1729, 1602, 1512 and 1240 cm⁻¹ while the intensity of cellulose bands including the crystallinity-associated peaks at 1432 and 1320 cm⁻¹ were preserved. The SEM images further confirmed significant transformation with distorted vascular tissue and exposed cellulose fibrils indicating extensive defibrillation. Full article

The study presents the results of research on the preparation of biopolyols based on organosolv lignin and their application in the synthesis of rigid polyurethane foams. The research was conducted in order to develop a sustainable alternative to the previously used ethylene carbonate in lignin oxyalkylation processes. The main objective was to replace the previously used ethylene carbonate with propylene carbonate in a stoichiometrically equivalent molar amount in order to reduce polyol viscosity and improve the performance properties of the resulting foams. The syntheses were carried out without the need for isolation and purification of intermediate products. Polyols analogous to those described previously were obtained and subsequently used for the preparation of rigid polyurethane foams employing polymeric diphenylmethane diisocyanate. The properties of the obtained foams were investigated and compared with those of foams prepared from ethylene carbonate-based polyols. The results demonstrated that the use of propylene carbonate leads to the formation of lower-viscosity polyols, facilitating homogenization of the reaction systems and enabling the production of foams with advantageous performance characteristics, generally superior to those of foams based on ethylene carbonate. The obtained materials constitute a promising alternative to conventional polyurethane foams derived from petrochemical raw materials. Full article

The valorization of secondary biomass streams is an important step toward more resource-efficient biorefinery concepts and reduced dependence on fossil-based materials. In this study, agricultural and forest residues, namely Atlas cedar cones, mixed conifer cones, hazelnut shells, walnut shells, coffee silverskin, and cocoa shells, were investigated as feedstocks for producing colloidal lignin particles. Lignin-rich extracts were obtained by Organosolv pretreatment using 60 wt% aqueous ethanol, followed by particle formation through solvent shifting and purification by ultrafiltration. A particular novelty of this work is that highly different feedstocks were processed under identical Organosolv and solvent-shifting conditions, enabling a direct comparison of their suitability for colloidal lignin particle production within one consistent process route. The feedstocks differed markedly in extractive content and chemical profile, as shown by sequential Soxhlet extraction and qualitative GC-MS screening. Despite these differences in extract composition, solvent shifting yielded colloidal lignin particles with largely similar properties. Dynamic light scattering showed hydrodynamic diameters of 65–88 nm immediately after precipitation for all samples except cocoa shell, which formed strong agglomerates. The ultrafiltration step further introduced an industry-relevant downstream purification stage by removing most water-soluble low-molecular-weight compounds before product evaluation. After purification and redispersion, particle sizes ranged from 121 to 389 nm, indicating partial aggregation but overall successful recovery of stable colloidal dispersions. All purified particle suspensions exhibited comparable antioxidant activity in the FRAP (ferric reducing antioxidant power) assay, ranging from 12.3 to 18.4 mg lignin per mg ascorbic acid equivalents. These results demonstrate that even chemically diverse biomass side streams can be converted into purified colloidal lignin suspensions with similar colloidal behavior and functional performance. The findings highlight the potential of low-value agricultural and forest residues as promising raw materials for lignin-based antioxidant and material applications. Full article

This review evaluates pretreatment strategies for blending the organic fraction of municipal solid waste (OFMSW) with agricultural residues to recover fermentable sugars. Three mechanistic benefits have been hypothesized for such blends: ash-mineral pH buffering, endogenous protein reduction of non-productive cellulase–lignin binding, and inhibitor dilution. These mechanisms are inferred from analogous lignocellulosic systems rather than measured directly in OFMSW–agricultural residue combinations, and their translation into saccharification gains remains substrate- and pretreatment-specific. A synergy index framework with a four-tier classification (true synergy, additive, substitution, and process complementarity) is applied to reclassify the available evidence, alongside an assessment of pretreatment chemistry, enzymatic hydrolysis outcomes, and techno-economic feasibility. Integrated sequential pretreatment, particularly acid-catalyzed steam explosion and deacetylation with mechanical refining, proved most robust for heterogeneous feeds. The strongest Tier I synergy is found for SO₂-catalyzed steam explosion of hybrid poplar–wheat straw (SI 1.29–1.33; 22% monomeric sugar gain). OFMSW combined with organosolv beechwood cellulose at 35–45% OFMSW reached 58–68% saccharification (44–46 g sugar L⁻¹), a Tier III–IV outcome. Matched-control saccharification data for OFMSW–agricultural residue blends specifically have not been reported. Co-processing corn stover with wet organic waste reduced CO₂ mitigation cost from $236 to $67 per ton CO₂-eq under bio-CNG upgrading. Formal synergy quantification, blend-specific inhibitor profiling, and high-solids process intensification are the central prerequisites for commercial translation. Full article

Lignin, the second most abundant polymer, remains largely underutilized, with nearly 90% of industrial lignin being combusted for energy due to its low phenolic hydroxyl content and structural heterogeneity of conventional extraction methods. The present study proposes a synergistic extraction method integrating sequential hydrothermal and twin-screw extrusion pretreatment followed by aqueous ethanol organosolv extraction. Three pretreatment strategies—hydrothermal pretreatment, twin-screw extrusion pretreatment, and sequential hydrothermal and twin-screw extrusion pretreatment—were compared. The sequential pretreatment exhibited the most favorable performance. Upon organosolv extraction, a lignin extraction rate of 67.9% was achieved, representing a 20.8% increase over that of the raw material. Extensive β-O-4′ bond cleavage during the integrated process liberated phenolic hydroxyl groups. This elevated the total phenolic hydroxyl content to 3.43 mmol·g⁻¹, representing a 63.3% increase relative to lignin derived from raw material. Concurrently, this bond cleavage yielded lignin with a narrower molecular weight distribution, indicating enhanced structural homogeneity. Additionally, cellulose retention after lignin extraction reached 88.9%. Mass-balance calculations indicated that 1000 g of raw material yielded 82.5 g of xylose and xylooligosaccharides, 148.2 g of highly active lignin, and cellulose-enriched solid residues, thereby facilitating the comprehensive utilization of the three primary components of lignocellulosic biomass. Full article

This review explores the biological properties and application potential of native, technical, and modified lignins, with a focus on their antioxidant, antimicrobial, and anti-inflammatory activities. Native lignin generally preserves more of its original phenolic architecture and thus shows stronger intrinsic biological activity. This is likely due to its more homogeneous structure, which makes its physicochemical behavior more predictable compared with highly processed technical lignins. Among technical lignins, organosolv and soda lignin appear the most promising due to their sulfur-free nature, lower condensation, and higher reactivity. At the monomer level, catechol-type phenolics show the highest antioxidant potential, while vanillin remains the most attractive lignin-derived monomer because it combines bioactivity with direct application potential in food, pharmaceutical, and cosmetic systems. Comparison of modification strategies indicates that phenolic grafting, esterification, and carboxylation are more practical for scale-up than complex multistep polymer grafting. In particular, gallic acid grafting produced some of the strongest results, including near-complete 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) scavenging, 98.7% 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical inhibition, and a fourfold increase in phenolic hydroxyl content, whereas other modified lignins also showed improved antimicrobial and anti-inflammatory effects. Overall, mild and green lignin modification, especially with food-safe phenolic compounds, appears to be the most promising strategy for future food and human health applications. Full article

Wheat straw is an abundant agricultural residue with high potential for carbohydrate-based bioconversion, yet its efficient utilization is limited by lignocellulosic recalcitrance. This study systematically investigated Organosolv extraction of wheat straw (Triticum aestivum) with the goal of achieving near-complete enzymatic hydrolysis at minimized process severity and energy demand. Process severity was evaluated using the P-Factor concept. In preliminary screening, acid catalysts and liquor ratios were assessed. Strong acids clearly outperformed weak acids: at comparable severity, 5% (w/w, DM) H₂SO₄ or p-toluenesulfonic acid (PTSA) yielded glucose yields of 83 ± 2.4% and 81 ± 6.2%, respectively, whereas weak acids (phosphoric, lactic, acetic) and a catalyst-free control resulted in only ~20–41% glucose yield. Liquor ratio strongly affected extraction performance; a ratio of 1:19 provided the highest glucose yield (85 ± 1.4%) and robust mixing compared to 1:12–1:15 (67–68%). Two novel pretreatment strategies applied prior to Organosolv extraction, namely Hot-Water Pretreatment (HWP) and Water Pretreatment (WP), significantly increased hydrolysability compared to untreated straw (58 ± 3%), reaching 79 ± 2% for HWP and 86 ± 5% for WP. DoE-based experiments (135–170 °C; P-Factor 3.0–4.0) showed that increasing temperature from 135 to 150 °C markedly improved hydrolysability (e.g., WP: 74 ± 3% to 96 ± 3%), while further increasing to 170 °C provided no additional benefit. Response-surface modeling predicted a maximum hydrolysability of approximately 88% for HWP but complete hydrolysis for WP within 152–170 °C, indicating a broad operational window. Overall, combining simple Water-based Pretreatment with severity-optimized Organosolv extraction enables energy-efficient, near-complete hydrolysis at lower operating temperatures, reducing both energy demand and pressure requirements, and thereby offering advantages in process cost and scalability. Full article

Hemp hurds (HHs), a lignocellulosic agricultural waste, have the potential for bioconversion into bio-based products. However, the matrix structure of biomass comprising cellulose, hemicellulose, and lignin makes cellulose inaccessible. Pre-treatment is essential for accessing cellulose by removing lignin, hemicellulose, and extractives. This study compares lignocellulose structure modification of HH using low-concentration chemical pretreatment methods, including organosolvent, 60% ethanol (EtOH), 3% hydrogen peroxide with 3% ammonia (H₂O₂/NH₃), and 2% sodium hydroxide (NaOH) with sonication. X-ray diffractor (XRD) analysis, using Segal method as a guide, showed that post treatments, the crystallinity index increased from 39.26% in untreated HH to 65.80% for NaOH-treated hurds. Polysaccharide content decreased compared to HH, attributed to the combination of solubilisation of hemicellulose, degradation of amorphous carbohydrates, and loss of sample during treatment wash. Although there was a reduction in polysaccharide content compared to HH, NaOH treated HH showed the highest total carbohydrate content of 48.6% and the most disrupted surface structure, based on scanning electron microscope (SEM) images at 2000× magnification. Fourier-transform infrared spectrophotometer (FTIR) analysis indicated a reduction in lignin and hemicellulose peaks for NaOH and H₂O₂/NH₃ treatments, while thermogravimetric analyser (TGA) and derivative thermogravimetric analysis (DTG) results showed improved thermal stability for NaOH-treated samples. The ultrasound-assisted NaOH-treated sample had the most structural disruption in recovered solid fraction, based on comparative compositional and structural analyses. This gives a guide on the selection of pretreatment to pursue for HH processing. Full article

Orange processing generates large amounts of waste orange peels (WOPs), which are a valuable source of bioactive polyphenols. This study investigated the use of mild (urea) and strong (sodium hydroxide) alkaline catalysts to enhance polyphenol extraction via an ethanol-based organosolv process. First, the two catalysts were evaluated in terms of process performance, extraction kinetics, and treatment severity. Subsequently, response surface methodology was applied to optimize the conditions, and the obtained extracts were characterized for their polyphenolic profile and antioxidant activity. The sodium hydroxide (SoHy)-catalyzed treatment, using 70% ethanol as solvent, was the most effective, yielding 33.4 ± 1.7 mg of total polyphenols (as gallic acid equivalents) per gram of dry mass. For both catalysts tested, the yield followed a severity-dependent linear model. Liquid chromatography–mass spectrometry of extracts produced under optimized conditions showed that hesperidin was the predominant polyphenolic constituent, but the SoHy-catalyzed treatment resulted in the generation of three novel compounds, tentatively identified as ethyl esters of p-coumaric, ferulic and sinapic acids. Such an effect was not observed in the extracts produced with the urea (Ur)-catalyzed treatment. This compositional modification was reflected on both the antiradical activity and ferric-reducing power, which were found to be significantly enhanced in the extracts produced via the SoHy-catalyzed treatment. These findings highlight how treatment conditions can be tuned to modify the polyphenolic composition of WOP extracts and reinforce antioxidant activity. Such insights could support the development of WOP valorization strategies within integrated biorefineries. Full article

This study presents a simple method for producing chemically crosslinked porous materials from lignocellulosic fibers with different particle sizes and lignin contents. Porous materials were prepared from organosolv pulp (OP), kneaded organosolv pulp (KOP), lignin-rich microfibrillated cellulose (LMFC), and enzyme cellulose nanofiber (ECNF) and were crosslinked using epichlorohydrin, glutaraldehyde, and glycerol diglycidyl ether (GDE). Among the crosslinkers, GDE provided the best dimensional stability and elastic recovery after repeated compression–recovery cycles in water. Notably, KOP-based porous materials outperformed those derived from LMFC and ECNF, despite being produced via a simple kneading process without energy-intensive fibrillation. KOP-derived materials exhibited excellent dimensional stability and high water absorption exceeding 5890%, demonstrating strong potential for bio-based absorbent applications such as hygiene and packaging. Full article

The study explores γ-valerolactone (GVL) pulps as a sustainable approach to producing microfibrillated (MFC) and nanofibrillated (NFC) cellulose from sugarcane bagasse, a widely available agro-industrial by-product. Pulp was obtained by acid-catalyzed organosolv delignification with a GVL–water system. MFC was generated through a simple disc refiner, while NFC was produced by TEMPO-mediated oxidation followed by mechanical treatment in a colloidal mill. NFC and MFC produced using the same methodology from a commercial sugarcane totally chlorine-free (TCF) soda–anthraquinone (soda–AQ) pulp served as a reference. Structural and physicochemical characterization involved optical transmittance, turbidity, conductimetry, X-ray diffraction, viscosity, FTIR, carboxyl content, cationic demand, degree of polymerization, and morphology by scanning electron microscopy (SEM). Results demonstrated that xylan and residual lignin contents influenced MFC formation, and the NFC showed properties comparable to those of the commercial pulp with fewer fibrillation passes. The study highlights GVL pulping as a greener, efficient alternative to conventional processes, opening new pathways for producing viscosity-controlled nanocellulose suspensions suitable for advanced applications. Full article