Search Results (9)

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 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

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

Developing efficient, clean, and sustainable lignocellulose pretreatment technologies is essential for second-generation biofuel production. In this study, we attempted to use downstream-separated binary acetone-water, n-butanol-water, and ethanol-water solutions as the initial liquor for upstream organosolv pulping, in order to achieve the efficient and economic closed-circuit clean fractionation of the lignocelluloses for biological acetone–butanol–ethanol (ABE) production. Parameters, including concentration and temperature of the organosolv pulping, were optimized systematically. Results indicated that the 50 wt% ethanol and 30 wt% acetone aqueous solutions and pulping at 200 °C for 1 h exhibited better corn stover fractionation performances with higher fermentable sugar production. The total monosaccharide recovery (including glucose and xylose) was 50.92% and 50.89%, respectively, in subsequent enzymatic saccharification. While pulping corn stover using n-butanol solution as initial liquor showed higher delignification 86.16% (50 wt% of n-butanol and 200 °C for 1 h), the hydrolysate obtained by the organosolv pulps always exhibited good fermentability. A maximized 15.0 g/L of ABE with 0.36 g/g of yield was obtained in Ethanol-200 °C-50% group, corresponding to 112 g of ABE production from 1 kg of raw corn stover. As expected, the lignin specimens fractionated by closed-circuit organosolv pulping exhibited narrow molecule weight distribution, high purity, and high preservation of active groups, which supports further valorization. This novel strategy tightly bridges the upstream and downstream processes of second-generation ABE production, providing a new route for ‘energy-matter intensive’ and environmentally friendly lignocelluloses biorefineries. Full article

Corncobs, produced globally at over 200 million tons annually with 11–18% lignin content, represent an abundant and underexploited lignocellulosic resource for sustainable lignin valorization. In this study, two distinct extraction methodologies, alkaline treatment using sodium hydroxide and an organosolv process with a 50:50 ethanol/water mixture, were systematically compared for their efficiency in isolating lignin from corncobs. Both protocols achieved high yields, up to 82% for alkaline and 84% for organosolv extraction under optimized conditions. The resulting lignins displayed notable differences in chemical structure and physical properties, as revealed by spectroscopic and thermal analyses, highlighting their divergent potential for downstream applications. To evaluate the suitability of these lignins to biocatalytic upgrading, post-extraction enzymatic treatment was performed using Pycnoporus cinnabarinus laccase (EC 1.10.3.2). Significant structural modifications were observed in alkaline-extracted lignin, as determined by FTIR spectroscopy, while organosolv lignin remained largely unaltered, a difference attributed to its lower aqueous solubility at the enzyme’s optimal pH. These results demonstrate the critical impact of extraction conditions on lignin reactivity and suitability for enzymatic tailoring. This work underscores the potential for holistic corncob valorization within integrated biorefinery frameworks. Selective extraction and targeted enzymatic modification not only facilitate efficient by-product utilization but also expand the prospects for producing versatile bio-based materials, thereby advancing the transition toward a sustainable, circular bioeconomy. Full article

Water-soluble azo derivatives of lignin were synthesized by the azo coupling reaction using organosolv ethanol lignin and diazonium salts based on sulfanilic acid and p-nitroaniline. The structure of azo derivatives of lignin were studied by nuclear magnetic resonance, Fourier-transform infrared spectroscopy, and gel permeation chromatography. It was found that the azobenzene bonds formed in the azo coupling reaction of macromolecules impart the photosensitive properties to the synthesized polymers via cis–trans photoisomerization of the diazobenzene group. It was shown experimentally that the synthesized polymers exhibited good solubility both in the aqueous media in a wide (2–12) pH range and in DMSO and THF organic solvents, which opens up new prospects for their application. Full article

Olive leaves (OLL) are an agri-food waste that may be regarded as a bioresource rich in bioactive polyphenolic metabolites. In this examination, simultaneous organosolv treatment/extraction of OLL polyphenols at elevated temperatures (>110 °C) has been optimized using glycerol, but also two glycerol-based deep eutectic solvents (DES). The assessment of the processes was based on the severity factor and the extraction efficiency factor. In any case, the treatment/extraction with a DES composed of glycerol and citric acid (GL-CA) was found to be the less severe and the most effective in recovering polyphenols from OLL, giving a yield of 69.35 mg gallic acid equivalents per g dry mass. On the other hand, liquid chromatography-mass spectrometry investigation revealed that extraction with either DES used provided extracts with differentiated polyphenolic profile than that obtained when water or 60% (v/v) aqueous ethanol was used as solvents. On the ground of these analysis, evidence emerged regarding hydrolysis of flavone glucosides when the treatment was performed with an alkaline DES composed of glycerol and sodium citrate. The extracts produced also exhibited diversified antioxidant activity, a fact putatively attributed to the different polyphenolic profiles. It was concluded that organosolv treatment/extraction of OLL for polyphenol recovery opens new endeavors in the valorization of this particular waste, but metabolite stability is an issue that merits profounder study. Full article

The core objective of this work was to take advantage of the unexploited wheat straw biomass, currently considered as a broadly available waste stream from the Greek agricultural sector, towards the integrated valorization of sugar streams for the microbial production of polyunsaturated omega-3 fatty acids (PUFAs). The OxiOrganosolv pretreatment process was applied using acetone and ethanol as organic solvents without any additional catalyst. The results proved that both cellulose-rich solid pulp and hemicellulosic oligosaccharides-rich aqueous liquid fraction after pretreatment can be efficiently hydrolyzed enzymatically, thus resulting in high yields of fermentable monosaccharides. The latter were supplied as carbon sources to the heterotrophic microalga Crypthecodinium cohnii for the production of PUFAs, more specifically docosahexaenoic acid (DHA). The solid fractions consisted mainly of hexose sugars and led to higher DHA productivity than their pentose-rich liquid counterparts, which can be attributed to the different carbon source and C/N ratio in the two streams. The best performance was obtained with the solid pulp pretreated with ethanol at 160 °C for 120 min and an O₂ pressure of 16 bar. The total fatty acids content reached 70.3 wt% of dried cell biomass, of which 32.2% was DHA. The total DHA produced was 7.1 mg per g of untreated wheat straw biomass. Full article

In this study, the chemical pretreatment method using ethanol organosolv with hydrogen peroxide was investigated to improve enzymatic saccharification of corn stover. The pretreatment method using ethanol with hydrogen peroxide in a flow-through reaction was proposed to lower the reaction severity such as the pretreatment temperature. With the same reaction time, the pretreatment process using organosolv (30 wt.% ethanol) containing 1 wt.% hydrogen peroxide at 150 °C resulted in a similar conversion yield as the result of the alkali pretreatment method using 15 wt.% aqueous ammonia at 170 °C. When corn stover was pretreated with 30 wt.% ethanol solution containing 5 wt.% hydrogen peroxide, a glucose conversion yield of 69.7 wt.% and glucose production of 23.8 g were achieved. Full article