Fabrication and characterization of an alginate-based film incorporated with cinnamaldehyde for fruit preservation.

Sodium alginate (SA) is widely used in the food, biomedical, and chemical industries due to its biocompatibility, biodegradability, and excellent film-forming properties. This article introduces a simple method for preparing uniform alginate-based packaging materials with exceptional properties for fruit preservation. The alginate was uniformly crosslinked by gradually releasing calcium ions triggered by the sustained hydrolysis of gluconolactone (GDL). A cinnamaldehyde (CA) emulsion, stabilized by xanthan without the use of traditional surfactants, was tightly incorporated into the alginate film to enhance its antimicrobial, antioxidant, and UV shielding properties. The alginate-based film effectively blocked ultraviolet rays in the range of 400-200 nm, while allowing for a visible light transmittance of up to 70 %. Additionally, it showed an increased water contact angle and decreased water vapor permeability. The alginate-based film was also employed in the preparation of coated paper through the commonly used coating process in the papermaking industry. The alginate-based material displayed excellent antioxidant properties and antimicrobial activity against Escherichia coli, Staphylococcus aureus and Botrytis cinerea, successfully extending the shelf life of strawberries to 7 days at room temperature. This low-cost and facile method has the potential to drive advancements in the food and biomedical fields by tightly incorporating active oil onto a wide range of biomacromolecule substrates.

Nano-copper ions assembled cellulose-based composite with antibacterial activity for biodegradable personal protective mask.

The current SARS-CoV-2 pandemic has resulted in the widespread use of personal protective equipment, particularly face masks. However, the use of commercial disposable face masks puts great pressure on the environment. In this study, nano-copper ions assembled cotton fabric used in face masks to impart antibacterial activity has been discussed. To produce the nanocomposite, the cotton fabric was modified by sodium chloroacetate after its mercerization, and assembled with bactericidal nano-copper ions (about 10.61 mg·g-1) through electrostatic adsorption. It demonstrated excellent antibacterial activity against Staphylococcus aureus and Escherichia coli because the gaps between fibers in the cotton fabric allow the nano-copper ions to be fully released. Moreover, the antibacterial efficiency was maintained even after 50 washing cycles. Furthermore, the face mask constructed with this novel nanocomposite upper layer exhibited a high particle filtration efficiency (96.08% ± 0.91%) without compromising the air permeability (28.9 min·L-1). This green, economical, facile, and scalable process of depositing nano-copper ions onto modified cotton fibric has great potential to reduce disease transmission, resource consumption, and environmental impact of waste, while also expanding the range of protective fabrics.

Modulation of composite hydrogel consisting of TEMPO-oxidized cellulose nanofibers and cationic guar gum.

The applications of hydrogels are prominently affected by the modulation of their structure and performance. We herein systematically implemented the modulation of an all-polysaccharide hydrogel consisting of TEMPO-oxidized cellulose nanofibers (TOCN) and cationic guar gum (CGG). Four different factors including the carboxylate content and size of TOCN, the freezing-thawing treatment and solid content of hydrogel were studied to disclose their influence on the structure and property of TOCN/CGG hydrogel. The results indicated that the increase of carboxylate content of TOCN, the number of freezing-thawing cycles and solid content all increased the crosslinking density of hydrogel as a result of the improved interactions. Accordingly, the hydrogels exhibited more compact structures and enhanced rheological properties. The influence of TOCN size on the hydrogel structure and property was demonstrated to be dependent on the compromise between the exposed functional groups of TOCN and their ability in generating entanglements inside the hydrogel. This work helps shed light on the modulation of hydrogel structure and performance, which might facilitate the exploration of hydrogel applications.

Preparation of Cellulose Nanocrystals by Synergistic Action of Ionic Liquid and Recyclable Solid Acid under Mild Conditions.

Cellulose nanocrystals (CNCs) are nanoscale particles made from cellulose. They have many unique properties such as being lightweight, stiff, and renewable, making them promising for a variety of applications in a wide range of industries, including materials science, energy storage, and biomedicine. In this paper, a two-stage (swelling-SA-catalyzed) method including IL pretreatment and solid acid hydrolysis process was developed to extract CNCs with high purity and good thermal stability from microcrystalline cellulose (MCC). In the first stage, the swelling of MCC in ionic liquid was studied with the assistance of ultrasonication, and it was found that the amorphous regions became more disordered while the crystalline areas were selectively retained under the conditions of 30 min of reaction time, 45 °C of temperature, 2% of ionic liquid water content and 1:4 mass ratio of cellulose to ionic liquid. CNCs were extracted using solid acid hydrolysis, with a 45 wt% solid acid to cellulose ratio and a 5.0 h hydrolysis process at 45 °C. The morphology, crystallinity, surface characteristics and thermo stability of the sample were characterized by atomic force microscopy (AFM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA), respectively. Results demonstrated the highly thermostable CNCs were successful extracted with rodlike shape of 300 ± 100 nm in length and 20 ± 10 nm in width. Solid acid recovery and reuse were also studied, revealing a promising candidate that can reduce the environmental impact associated with chemical products.

Biofiber waste derived zwitterionic and photocatalytic dye adsorbent: Switchable selectivity, in-situ degradation and multi-tasking application.

Dye wastewater and discarded biofiber have brought huge pressure to sustainable developments of ecology and economy. By utilizing dopamine chemistry and benzophenone mediated "grafting onto" atom transfer radical polymerization (ATRP), this work reported a biomass adsorbent containing discarded wool substrate, photocatalytic PDA coating and zwitterionic polymer brushes for dyes removal. The grafted zwitterionic polymer brushes impart the material with not only high adsorption capacity and rapid adsorption rate, but also switchable adsorption selectivity and pH-controlled regeneration capability. Benefiting from such outstanding adsorption performance and excellent free-standing property, the adsorbent could fulfill diversified needs of both static and dynamic adsorptions. Under daylight, the constructed photocatalytic PDA coating could in-situ degrade the captured pollutant, thus achieving consecutive adsorption-degradation-regeneration utilization. Furthermore, through simple dip-coating and cleaner UV-irradiation techniques, the preparation process could be scaled up. This work contributes to both the upcycling of discarded biofiber waste and the development of advanced biomass adsorbent.

Multi-stimuli-responsive photonics films based on chiral nematic cellulose nanocrystals.

Multiple-stimuli-responsive bio-based materials have received considerable attention for intelligent packaging and anti-counterfeiting applications. Herein, we present a unique biobased photonics film with multi-stimuli responsive behavior based on cellulose nanocrystals (CNCs), sorbitol (S) and anthocyanin (Anth). The resulting photonics film exhibits multi-stimuli responsive behavior to humidity, solvent and pH stimuli. Notably, the photonics film showed dramatic invertible color from blue to fuchsia and high sensitivity at a relative humidity from 50% to 100%. Moreover, the photonics film exhibited fast response and good reversibility under different ethanol concentrations. Significant color changes of the photonics film were also observed in response to pH change in the range of 2 to 12. Particularly, the humidity, solvent and pH responsiveness of the photonics film did not interfere with each other.

Efficiently conversion of raw lignocellulose to levulinic acid and lignin nano-spheres in acidic lithium bromide-water system by two-step process.

Herein, acidic concentrated lithium bromide-water system was efficiently carried out to synthesize levulinic acid (LA) from raw lignocellulose by two-step treatment. Saccharification was processed in 1st step, and 80.96 wt% glucose and 85.60 wt% xylose were yielded based on their theoretical yield from poplar at 110 °C for 20 min. The hydrolysate after solid residual lignin (SRL) separation was converted into LA and furfural by thermal treatment (130 °C) in the 2nd step, where 67.0 wt% LA and 48.0 wt% furfural were yielded. The SRL in 1st step, with high hydrophobicity and uniform dispersity, was used to prepare lignin nanoparticles (LNPs), which showed tailored size (100-200 nm diameters) and morphology in solid or hollow structure with single hole. Additionally, the residue in 2nd step was suggested as biochar. So far, this study offered a simple pathway for utilization of raw lignocellulose in water system, resulting in high yields of LA and LNPs.

A hydrotrope pretreatment for stabilized lignin extraction and high titer ethanol production.

The biomass pretreatment strategies using organic acids facilitate lignin removal and enhance the enzymatic digestion of cellulose. However, lignin always suffers a severe and irreversible condensation. The newly generated C-C bonds dramatically affect its further upgrading. In this study, we used a recyclable hydrotrope (p-Toluenessulfonic acid, p-TsOH) to dissolve lignin under mild condition and stabilized lignin with a quenching agent (formaldehyde, FA) during extraction, achieving both value-added lignin extraction and efficient enzymatic saccharification of cellulose. Approximately 63.7% of lignin was dissolved by 80% (wt. %) p-TsOH with 1.5% FA addition at 80 °C, 30 min. The obtained lignin was characterized by FTIR spectroscopy, TGA, 2D HSQC NMR spectroscopy, and GPC. The results indicated that the extracted lignin exhibited excellent properties, such as light color, a low molecular weight (Mw, 5371 g/mol), and a narrow polydispersity (Mw/Mn, 1.63). The pretreated substrate was converted to ethanol via a quasi-simultaneous saccharification and fermentation process (Q-SSF). After fermentation of 60 h, the ethanol concentration reached 38.7 ± 3.3 g/L which was equivalent to a theoretical ethanol yield of 82.9 ± 2.2% based on the glucan content, while the residual glucose concentration was only 4.69 ± 1.4 g/L. In short, this pretreatment strategy protected lignin to form new C-C linkages and improved the enzymatic saccharification of glucan for high-titer ethanol production.

Chiral Cellulose Nanocrystal Humidity-Responsive Iridescent Films with Glucan for Tuned Iridescence and Reinforced Mechanics.

The fabrication of biomimetic photonic materials with environmental stimuli-responsive functions from entirely biobased materials is becoming increasingly challenging with the growing demand for biodegradable materials. Herein, the effect of glucan with different molecular weights on the mechanical performance and tunable structural color of iridescent CNC composite films was investigated. The existence of glucan did not influence the self-assembly performance of CNCs, but rather led to an improvement in the mechanical performance, enabling cholesteric CNC composite films with an adjustable structural color. Simultaneously, the iridescent films showed a conspicuous redshift and enlarged initial pitch without obstruction of the chiral structure. In response to environmental humidity, the structural colors of the iridescent composite films can be changed by regulating their chiral nematic structure. In particular, the films demonstrate a reversible structural color change between blue and red at RH between 50 and 98%. The resulting biobased iridescent composite films have potential applications in decorative coating, optical and humidity sensing, and anticounterfeiting.

Efficient homogeneous TEMPO-mediated oxidation of cellulose in lithium bromide hydrates.

An appropriate cellulose-dissolving solvent is critical for the homogeneous oxidation of cellulose using TEMPO (2, 2, 6, 6-tetramethylpiperidine-1-oxyl)-mediated system. Herein, TEMPO/NaClO/NaClO2 system in lithium bromide hydrates (LBHs) was developed for the homogeneous selective-oxidation of cellulose, which was two-stage protocol involving cellulose dissolution and homogeneous oxidation. Specifically, cellulose was firstly dissolved in LiBr·3.5H2O and offered the optimal pH (5.6) for the subsequent TEMPO/NaClO/NaClO2 oxidation without precipitation of the cellulose chains. Effect of reaction conditions on cellulose oxidation was investigated. The results showed that high degree of oxidation (DO) and evenly distributed carboxyl could be achieved. The particle size gradually decreased with DO, and oxidized cellulose with high water solubility and amorphous structure could be obtained. Furthermore, FT-IR, 13C NMR and fractionation analysis verified that cellulose was successfully converted and the carboxyl uniformly distributed onto the cellulose chains. This TEMPO-mediated system using LBHs as solvent presented an efficient method on the homogeneous selective oxidation of primary hydroxyl in cellulose.

Husbandry waste derived coralline-like composite biomass material for efficient heavy metal ions removal.

The resource utilization of biological solid waste is crucial for practical environmental remediation. By comprehensively utilizing LiBr treatment and dopamine chemistry, herein the cow dung waste was successfully converted into the composite biomass material for efficient heavy metal ions removal. A selective etching mechanism of cellulose was discovered in the LiBr treatment process, achieving the large-scale preparation of coralline-like porous biomass material with hundred times increased specific surface. Benefiting from the co-deposition of polyethyleneimine and Fe3O4, the fabricated material showed significantly higher adsorption capacity (183.82 and 231.48 mg·g-1 for Cu2+ and Cd2+) than that of raw cow dung (0.95 and 1.25 mg·g-1 for Cu2+ and Cd2+). Furthermore, this composite biomass adsorbent also exhibited rapid adsorption equilibrium, magnetic separation capability, monolayer chemisorption feature and feasible recycling use. Collectively, this work contributes to both the resource utilization of husbandry solid waste and the development of advanced biomass adsorbent.

Effect of Cellulose Nanocrystal Addition on the Physicochemical Properties of Hydroxypropyl Guar-Based Intelligent Films.

As an important functional material in food industry, intelligent packaging films can bring great convenience for consumers in the field of food preservation and freshness detection. Herein, we fabricated pH-sensing films employing hydroxypropyl guar (HPG), 1-butyl-3-methylimidazolium chloride (BmimCl), and anthocyanin (Anth). Besides, the effects of adding cellulose nanocrystals (CNC) into the composite films upon the films' structures and physicochemical properties are elucidated. The addition of CNC promoted more compact film structures. Moreover, CNC dramatically improved several properties of the pH-sensing films, including the distinguishability of their color changes, sensitivity to pH, permeability to oxygen and water vapor, solvent resistance, durability, and low-temperature resistance. These results expand the application range of pH-sensing films containing CNC in the fields of food freshness detection and intelligent packaging.

Synthesis and characterization of temperature/pH dual sensitive hemicellulose-based hydrogels from eucalyptus APMP waste liquor.

In this investigation, a variety of innovative temperature/pH-sensitive hydrogels consisting of hemicellulose (extracted from APMP waste liquor) and acrylic acid/acrylamide monomers were synthesized via free radical polymerization for water retention agents and controlled release. The results showed that the hydrogel polymer was chemically cross-linked and entangled to form a three-dimensional network structure, and the monomer successfully grafted on the hemicellulose chain. The content of crosslinkers and monomers had obvious effects on the swelling ratio of hydrogel. The sensitivity of the hydrogel was determined according to the change of the swelling ratio of the hydrogel under different temperature and pH conditions, combined with the chemical structure analysis of the hydrogel, and explain its sensitivity mechanism. Finally, after 6 days at 25 °C and pH 6, the swelled hydrogel still retained 79.46 % of the moisture, which proved that it has high water retention ability.

Fabrication of environmental humidity-responsive iridescent films with cellulose nanocrystal/polyols.

Herein, we fabricated flexible and humidity-sensitive composite films employing cellulose nanocrystal (CNC) and polyols, i.e., glycerol (G), xylitol (X) and sorbitol (S). The effects of polyols with different molecular weights on the structure, optical properties, mechanical strength and humidity response of the composite films were investigated. Notably, the CNC-S film exhibited obvious reversible colour changes from light green to red upon a relative humidity (RH) change from 30 % to 95 %. Moreover, it was found that the composite films had a large colour-change range, good reversibility (>10 cycles), and excellent stability (>10 weeks). Overall, the results demonstrated that the CNC-S composite film can be used as a functional material for the preparation of flexible humidity sensors for the detection of environmental humidity changes in agriculture, industry, and other fields.

Biomedical Applications of Hemicellulose-Based Hydrogels.

BACKGROUND: Hydrogel has a three-dimensional network structure that is able to absorb a large amount of water/liquid and maintain its original structure. Hemicellulose (HC) is the second most abundant polysaccharide after cellulose in plants and a heterogeneous polysaccharide consisting of various saccharide units. The unique physical and chemical properties of hemicellulose make it a promising material for hydrogels. METHODS: This review first summarizes the three research hotspots on the hemicellulose-based hydrogels: intelligence, biodegradability and biocompatibility. It also overviews the progress in the fabrication and applications of hemicellulose hydrogels in the drug delivery system and tissue engineering (articular cartilage, cell immobilization, and wound dressing). RESULTS: Hemicellulose-based hydrogels have many unique properties, such as stimuliresponsibility, biodegradability and biocompatibility. Interpenetrating networking can endow appropriate mechanical properties to hydrogels. These properties make the hemicellulose-based hydrogels promising materials in biomedical applications such as drug delivery systems and tissue engineering (articular cartilage, cell immobilization, and wound dressing). CONCLUSION: Hydrogels have been widely used in biomedicine and tissue engineering areas, such as tissue fillers, drug release agents, enzyme encapsulation, protein electrophoresis, contact lenses, artificial plasma, artificial skin, and tissue engineering scaffold materials. This article reviews the recent progress in the fabrication and applications of hemicellulose-based hydrogels in the biomedical field.

Preparation of N, N, N-trimethyl chitosan via a novel approach using dimethyl carbonate.

N,N,N-trimehtyl chitosan (TMC) is a water-soluble derivate of chitosan, which has been widely used as a biomedical material due to its excellent biocompatibility, biodegradability and bacterial properties. To date, TMC can only be prepared by the quaternization of chitosan using alkyl halide or dimethyl sulfate. However, alkyl halide and dimethyl sulfate are highly toxic, cancerigenic for humans, and harmful to the environment. This paper puts forward a novel approach to preparing TMC using dimethyl carbonate as a methylation reagent in an ionic liquid. The as-synthesized O-methyl-free TMC was characterized using NMR, FTIR, XRD and TG analyses. The results showed that TMC with a degree of quaternization of 9.11% was successfully obtained and the crystallinity of chitosan decreased with the increasing degree of N-methylation, the thermal stability of TMC was lower than that of chitosan. Furthermore, the effects of the dose of ionic liquid and dimethyl carbonate were disscussed.

Enhancing cellulose dissolution in ionic liquid by solid acid addition.

It's challenging to dissolve natural cellulose in most solvents due to its highly ordered crystalline structure. In this paper, we developed an efficient cellulose dissolution system which incorporates solid acid (SA) with 1-butyl-3-methylimidizolium chloride (BmimCl). The results showed that addition of solid acid both Amberlyst® 15 and CsxH3-xPW12O40 could significantly enhance cellulose dissolution in BmimCl, which attributed to the synergistic action of free hydrogen proton from SA and chloride anion in BmimCl on hydroxyl groups of cellulose, and DMF as co-solvent also could facilitate cellulose dissolution in SA/BmimCl. In contrast to BmimCl system, the SA/BmimCl system for cellulose dissolution achieves better efficiency at mild treatment conditions and facile recovery of solvents. In addition, characterization of the regenerated celluloses showed that SA/BmimCl is a non-derivatizing solvent for cellulose, which helps achieve complete dissolution on crystalline cellulose. Attributed to its low cost and environmentally friendliness for biomass processing, SA/BmimCl systems is a promising and effective solvent system.

Recent research progress on preparation and application of N, N, N-trimethyl chitosan.

N,N,N-trimethyl chitosan (TMC) is a quaternized chitosan derivative with excellent solubility in aqueous solutions. It has been extensively studied as an absorption enhancer, antibacterial agent and gene vector due to its ability to form complexes with anionic gels or macromoleculars. However, the research which describes the process of TMC preparation and its new applications has not been fully reviewed. In this paper, recent progress regarding different TMC preparation methods and its characterization and application in different fields is presented. Key findings are compared and summarized and some topics for further study are suggested.

Efficient and selective adsorption of multi-metal ions using sulfonated cellulose as adsorbent.

Contamination of heavy metal in wastewater has caused great concerns on human life and health. Developing an efficient material to eliminate the heavy metal ions has been a popular topic in recent years. In this work, sulfonated cellulose (SC) was explored as efficient adsorbent for metal ions in solution. Thermo gravimetric analyzer (TGA), X-ray diffraction (XRD) and Fourier-transform infrared spectrometer (FTIR) first analyzed the characterizations of SC. Subsequently, effects of solution pH, adsorbent loading, temperature and initial metal ion concentration on adsorption performance were investigated. The results showed that sulfonated modification of cellulose could decrease the crystallinity and thermostability of cellulose. Due to its excellent performance of adsorption to metal ions, SC could reach adsorption equilibrium status within as short as 2min. In multi-component solution, SC can orderly removes Fe(3+), Pb(2+) and Cu(2+) with excellent selectivity and high efficiency. In addition, SC is a kind of green and renewable adsorbent because it can be easily regenerated by treatment with acid or chelating liquors. The mechanism study shows that the sulfonic group play a major role in the adsorption process.

High selective delignification using oxidative ionic liquid pretreatment at mild conditions for efficient enzymatic hydrolysis of lignocellulose.

Herein, the oxidative ionic liquid (IL) pretreatment for overcoming recalcitrance of lignocellulose with selective delignification was investigated, and the subsequent enzymatic hydrolysis was evaluated. IL pretreatment incorporating oxygen delignification could enhance lignin extraction with high selectivity at low carbohydrate loss. The dual-action of oxidative decomposition and dissolution by 1-butyl-3-methlimidazolium chloride (BmimCl) on biomass were synergistically acted, accounting for efficient recalcitrance removal. In addition, the mild oxidative IL treatment only slightly converted crystalline cellulose into amorphous structure, and the extensive extraction of the amorphous lignin and carbohydrate resulted to the expose of cellulose with high susceptibility. Correspondingly, the enzymatic hydrolysis of the pretreated lignocellulose was greatly enhanced. The oxidative IL treatment at mild conditions, collaborating BmimCl treatment with oxygen delignification is a promising and effective system for overcoming the robust structure of lignocellulose.