Aliphatic Hydroxyl Research Articles

Transferable Machine Learning Interatomic Potential for Bond Dissociation Energy Prediction of Drug-like Molecules.

We present a transferable MACE interatomic potential that is applicable to open- and closed-shell drug-like molecules containing hydrogen, carbon, and oxygen atoms. Including an accurate description of radical species extends the scope of possible applications to bond dissociation energy (BDE) prediction, for example, in the context of cytochrome P450 (CYP) metabolism. The transferability of the MACE potential was validated on the COMP6 data set, containing only closed-shell molecules, where it reaches better accuracy than the readily available general ANI-2x potential. MACE achieves similar accuracy on two CYP metabolism-specific data sets, which include open- and closed-shell structures. This model enables us to calculate the aliphatic C-H BDE, which allows us to compare reaction energies of hydrogen abstraction, which is the rate-limiting step of the aliphatic hydroxylation reaction catalyzed by CYPs. On the "CYP 3A4" data set, MACE achieves a BDE RMSE of 1.37 kcal/mol and better prediction of BDE ranks than alternatives: the semiempirical AM1 and GFN2-xTB methods and the ALFABET model that directly predicts bond dissociation enthalpies. Finally, we highlight the smoothness of the MACE potential over paths of sp3C-H bond elongation and show that a minimal extension is enough for the MACE model to start finding reasonable minimum energy paths of methoxy radical-mediated hydrogen abstraction. Altogether, this work lays the ground for further extensions of scope in terms of chemical elements, (CYP-mediated) reaction classes and modeling the full reaction paths, not only BDEs.

Ether Bond Formation in Waste Biomass–Derived, Value-Added Technical Hardwood Kraft Lignin Using Glycolic Acid

Ether bond formation in technical hardwood kraft lignin (THKL) by crosslinking using glycolic acid was investigated for bio-adhesive applications. Industrial hardwood kraft black liquor was used to extract the THKL utilized by acidification. Chemical and thermal properties of the THKL with and without crosslinking were analyzed by Fourier transform infrared (FTIR) spectroscopy, solid-state 13C cross-polarization/magic angle spinning nuclear magnetic resonance (13C CP/MAS NMR) spectroscopy, X-ray photoelectron spectroscopy (XPS), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). FTIR results revealed a new peak corresponding to the ether bond and hemiacetal formation due to crosslinking at 1075 cm-1 and 1324 cm-1. 13C CP/MAS NMR spectra revealed the presence of a higher number of ether bonds due to the reduced aromatic and aliphatic hydroxyl groups in THKL and new bonds formed at 62-64 ppm and 168-191 ppm due to crosslinking. XPS results revealed that new bonds were formed between glycolic acid and THKL, leading to increased atomic oxygen percentage and carbon–oxygen bonds in crosslinked THKL detected by peak intensity changes at 287.7 and 288.8 related to O–C–O and O–C=O. Also, the oxygen content increased from 14.88% to 31.76% due to bond formation. GPC confirmed a higher molecular weight and broader molecular-weight distribution of THKL. DSC and TGA curves of crosslinked THKL revealed exothermic behavior, high thermal stability, and low thermal degradation rate. Owing to a significant amount of kraft black liquor being generated by wood pulp industries and attractive chemical properties of THKL, THKL demonstrates promise as a raw material to produce green, sustainable bio-adhesives via the crosslinking of its different hydroxyl groups using glycolic acid.

Study on Thermal Behavior Characteristics and Microstructure Evolution Mechanism of Residual Coal Combustion Process in Deep High Initial Temperature Environment

ABSTRACT The shallow coal seam resources are gradually reduced, the depth of coal seam mining is increased, and the underground temperature is increased, which makes the risk of residual coal fire increase year by year. In order to explore the transformation path of functional groups during oxidation and the caloric release characteristics of residual coal in deep coal mine, the microcosmic changes of coal oxidation process in deep mine were analyzed by in situ diffuse reflectance (In situ FTIR) and electron spin resonance (EPR) experiments, and macroscopic characteristics such as characteristic temperature of residual coal were tested by synchronous thermal analysis experiment. In FTIR results, it is observed that hydroxyl groups, active aliphatic hydrocarbon structures, and active oxygen-containing groups are key chemical structures involved in the oxidation process of residual coal, displaying a strong correlation transformation phenomenon. This can be described as follows: oxygen absorption led to a negative correlation between aliphatic hydrocarbon structures and hydroxyl groups, while the conversion of aliphatic hydrocarbon structures into carboxyl and aldehyde groups resulted in a negative correlation between aliphatic hydrocarbons, carboxyl groups, and aldehyde groups. Active oxygen-containing functional groups showed a positive correlation. With the increased of free radical concentration, the type of free radicals increased and the linewidth (ΔH) increased. The high-temperature environment intensified thermal behavior tendencies, increased the number of active structures, and raised the risk of spontaneous combustion. The research results provided a theoretical basis for understanding the process of coal spontaneous combustion, and had important reference value for ensuring the safe mining of deep coal seams and implementing effective disaster prevention measures.

A novel antibacterial and anti-biofilm material: Biosynthetic silver nanoparticles mediated by extract from Oplopanax elatus adventitious roots

The search for plant resources involved in the biosynthesis of silver nanoparticles (AgNPs) is crucial for the diversity of AgNP materials. Oplopanax elatus is a valuable medicinal shrub and its adventitious root (AR) culture is a modern method for producing the raw material. To explore an efficient biosynthetic AgNPs, this study synthesized AgNPs using O. elatus AR extract (OE-AgNPs) and the characterization of OE-AgNPs was performed. Finally, the antibacterial and anti-biofilm effects of OE-AgNPs were investigated. The result showed that OE-AgNPs had an obvious absorption peak of nanosilver with a spherical shape and a silver-like face-centered cubic structure, which the OE-AgNPs were capped by compounds with aliphatic amine, amide, carbonyl, and hydroxyl groups of O. elatus AR extract, indicating a successful synthesis of OE-AgNPs. The 10–40 nm particles were the most abundant in the OE-AgNPs, accounting for 70%. OE-AgNPs had the strongest antibacterial activity against Escherichia coli and Pseudomonas aeruginosa among six bacterial species tested, with a minimum inhibitory concentration (MIC) of 0.75 μg/mL, and the cell contents of E. coli and P. aeruginosa leaked out by OE-AgNP treatment, and bacterial respiration was inhibited. After OE-AgNP treatment, biofilms of E. coli and P. aeruginosa were efficiently scavenged with a scavenging rate of more than 60%; the extracellular polysaccharide concentrations in biofilms were also ruduced. The findings of this study suggested that OE-AgNPs could be used as a potential antibacterial and antibiofilm substance to apply in the product production and indicated the feasibility of expanding the application of O. elatus ARs.

Green bio-based aprotic solvents for efficient fractionation of hemicellulose and targeted value addition of lignin

It is of great significance to inhibit the repolymerization of lignin when removing hemicellulose by acid pretreatment. Adding a lignin fragment scavenger is an effective method to inhibit its repolymerization. Here, the effect of a bio-based polar aprotic solvent, levulinic acid (Lev), and γ-valerolactone (GVL) coupled pretreatment system on the separation yield of poplar biomass components was investigated. The optimum pretreatment conditions were a Lev concentration was 7.0%, reaction temperature was 170 °C, pretreatment time was 60 min, and GVL concentration was 9.0%. The separation yield of hemicellulose was 84.54%, which was a 4.53% increase over that with Lev pretreatment. The retention yield of cellulose was 89.68%. In addition, the separation efficiency was significantly improved when the pretreatment time was reduced by 40 min. The reaggregation of lignin was suppressed under the condition of maximum hemicellulose separation. In the lignin samples the content of β-O-4 was as high as 47.81%. Simultaneously, the content of phenolic and aliphatic hydroxyl increased. The results revealed that Lev/GVL pretreatment had good hemicellulose separation selectivity and excellent lignin fragment removal efficiency. This provides a new strategy for suppressing adverse effects on the lignin structure in the efficient separation of hemicellulose in pretreatment.

Experimental study on effect of mudstone on spontaneous combustion of coal

The influence of mudstone on the spontaneous combustion of coal was investigated in this study. The effects of different proportions of mudstone on the characteristic temperature, thermal effect, thermal physical parameters, and combustion characteristic index of coal were analyzed by TG-DSC experiments and thermal physical parameter test experiments. The catalytic mechanism of mudstone on the active structure of coal oxidation was obtained by Fourier transform infrared spectroscopy. The results showed that an interaction exists between coal and mudstone, and different stages had different effects. The combustion characteristic index showed a trend of an initial increase followed by a decrease. The thermal conductivity and thermal diffusivity of MY-1 samples were larger than those of raw coal samples, indicating that a small amount of mudstone had the most obvious effect on coal combustion and played a promoting role in the heat transfer of coal samples. The carbon content of mudstone was much lower than that of coal, and the content of metals and their oxides and sulfides was higher. The content of aliphatic hydrocarbons and hydroxyl groups in the samples mixed with mudstone decreased. When coal coexists with a small amount of mudstone, the risk of spontaneous combustion of coal increases.

Catalyst identification for chemoselective phosphorylation of phenols and aliphatic alcohols

A screen was developed to identify catalysts that result in selective phosphoryl transfer to phenols and aliphatic alcohols. Optimization was performed by monitoring the impact of base, solvent, and molar equivalence on reactivity. We identified ZnBr2/Cs2CO3 as matched conditions for phenol phosphoryl transfer and Ti(OR)4/NiPr2Et as matched conditions for aliphatic alcohol phosphoryl transfer. The selectivity of the optimized conditions was then tested on the phosphorylation of 3-(4-hydroxyphenyl)-1-propanol (diol containing both an aliphatic and phenolic hydroxyl). In each case, the matched mono-phosphate product was formed in greater than 80% isolated yield.

Upgrading of kraft lignin with phosphoric acid purification: A promising route for the synthesis of renewable epoxy resins

Obtaining bioproducts of industrial interest from kraft lignin not only adds value to this residual biomass while reducing environmental impact, but also fosters the circular economy and promotes sustainable development. However, its use without the removal of ash, metals, sulfur, and nitrogen implies a reduction in the final product properties, limiting its applications. This study aims to present a simple and efficient route for the production of purified kraft lignin (LKP) with low ash 0.51% and total sulfur 0.74% content. It is produced from impure kraft lignin (LKI), with high ash 9.74% and total sulfur 1.39% content which was treated with hot H3PO4/H2O solution (dilute acid purification), aiming at the synthesis of lignin-based epoxy resins. Elemental Analysis of carbon (C), hydrogen (H), and nitrogen (N) (wt%); ash (wt%); total sulfur (wt%); moisture contents (wt%); X-ray Fluorescence; X-ray Diffraction; Infrared Spectroscopy; Thermogravimetric Analysis; and Differential Scanning Calorimetry showed that LKP improved its structural, functional; and chemical properties, particularly thermal properties: 17% increase initial decomposition temperature (Tonset), 18% decrease final decomposition temperature (Tendset), 14% increase maximum decomposition temperature (Tdmax.), 35% increase carbonaceous residue (CR) and 8% increase in the value of glass transition temperature (Tg). The limiting oxygen index (LOI) calculated for this sample was around 34%, thus configuring a “self-extinguishing” material. Moreover, its high phenolic and aliphatic hydroxyl content 8.02 mmol L−1, high aromaticity (H/C = 1.11), high weight average molar mass (Mw̅≅1900g mol−1), and ash and total sulfur low contents justify its use in the synthesis of lignin-based epoxy resins. A sample of LKP was tested in a classic epoxidation reaction to obtain the prepolymer denominated of lignin-based epoxy resin (E-LKP), whose epoxy equivalent weight (EEW) was around 3500 g mol−1, which is similar to that of the high molar mass epoxy resin, D.E.R. 668-20 2000, commercialized by Dow Chemical Company®. E-LKP was polymerized with a conventional curing agent (polyetheramine) to produce the cured lignin-based epoxy resin (R-ELKP) with good physical-chemical properties. The high glass transition temperature (Tg2 = 133 ºC), a good limiting oxygen index (LOI = 27%), and excellent aesthetic characteristics (homogeneity and high brightness) stand out. These promising results suggest that it is possible to develop cured lignin-based epoxy resin with properties comparable to cured petroleum-based epoxy resin. The use of purified kraft lignin to obtain materials (prepolymers and polymers epoxy, among others) will also favor the environment, developing greener and renewable products.

Aliphatic Alcohol Hydroxyl‐Directed One‐Pot Stepwise Synthesis: A Concise Synthesis of 1H‐pyrrolo[3,4‐b]quinoline‐1,3(2H)‐diones

AbstractA concise and flexible protocol to assemble structurally diverse 1H‐pyrrolo[3,4‐b]quinoline‐1,3(2H)‐diones (29 examples, 70–87% yields) has been developed via one‐pot stepwise synthesis. The potentially valuable quinine‐fused heterocycles were synthetized by utilizing aliphatic alcohol hydroxyl as directing group which promoted a sequential transformation to form functionalized aminomaleimides, and then underwent an I2‐oxidized tandem annulations. This route involved the formation of multiple new chemical bonds (C=N, 2C−N, C−C) in a one‐pot fashion under mild conditions.

Interaction between hydrophobic chitosan derivative and asphaltene in heavy oil to reduce viscosity of heavy oil

The high viscosity of heavy oil made it difficult to exploit and transport heavy oil in pipeline. In this research, N-[(2-hydroxy-3-trimethylammonium) propyl] O-stearoyl chitosan tetraphenylboride (sc-CTS-st) was synthesized from chitosan, 2, 3-epoxy-propyl trimethyl ammonium chloride, sodium tetraphenylboron and stearyl chloride. sc-CTS-st contains long chain saturated aliphatic hydrocarbon, hydroxyl group and benzene ring, which could be dissolved in heavy oil fully and interacted with asphaltene. At 50 °C, the viscosity of heavy oil could be reduced to 13,800 mPa·s at most, with a viscosity reduction rate of 57.54 %. SEM and XRD showed that sc-CTS-st could affect the supramolecular accumulation structure of asphaltenes. Using FT-IR, sc-CTS-st could interact with asphaltene in the form of hydrogen bonds using the polar parts of the molecule, thereby weakening the self-association between asphaltene molecules. Molecular simulation was used to demonstrate the interaction mechanism between chitosan derivatives and asphaltenes. sc-CTS-st interacted with asphaltene through chemical bonding and influenced the self-association of asphaltene molecules. In addition, the non-polar portion of sc-CTS-st molecules could form a coating on the outside of the asphaltenes stacking structure, thus shielding or reducing the polarity of the stacking structure surface.

Study on the thermal kinetics and microscopic characteristics of oxidized coal.

Revealing the characteristics of spontaneous combustion and re-combustion of oxidized coal is of great significance for the coal fire prevention and control. Synchronous Thermal Analyzer (STA) and Fourier Transform Infrared Spectrometer (FTIR) were used to measure the thermal kinetics and microscopic characteristics of coal samples with different oxidation degrees (unoxidized, 100 ℃, 200 ℃ and 300 ℃ oxidized coal). It is found that the characteristic temperatures decrease first and then increase with the increasing degree of oxidation. The ignition temperature of 100 ℃-O coal (oxidized at 100 ℃ for 6h) is relatively the lowest at 334.1 ℃. Pyrolysis and gas-phase combustion reactions dominate the weight loss process, while solid-phase combustion reactions are relatively minor. The gas-phase combustion ratio of 100 ℃-O coal is the highest at 68.56%. With the deepening of coal oxidation degree, the relative content of aliphatic hydrocarbons and hydroxyl groups gradually decreases, while that of oxygen-containing functional groups (C-O, C = O, COOH, etc.) increases first and then decreases, reaching the highest value of 42.2% at 100 ℃. Moreover, the 100 ℃-O coal has the minimum temperature at the point of maximum exothermic power of 378.5 ℃, the highest exothermic power of -53.09 mW/mg and the maximum enthalpy of -18,579J/g. All results show that 100 ℃-O coal has the highest risk of spontaneous combustion than the other three coal samples. This suggests that there is a maximum point of spontaneous combustion risk in the range of pre-oxidization temperatures of oxidized coal.

Separation and characterisation of glyceryl glycosides and lignin from acid-catalysed glycerol pretreatment hydrolysate of sugarcane bagasse

Acid-catalysed glycerol (ACG) pretreatment of biomass is one of the pre-treating techniques for the enzyme-mediated lignocellulosic biorefinery, while inadequate attention has been paid to the glycerol modified saccharides and lignin redistributed to the hydrolysate, nor their bioactive properties. In this study, a sequential process involving tetrahydrofuran (THF) extraction and carbon/celite adsorption-elution was employed to recover lignin and glyceryl glycosides (GG) from ACG hydrolysate. The physicochemical and structural properties of lignin were systematically explored, and were related to their antioxidation properties, the composition and moisturising activities of GG was investigated. Two types of lignin i.e., water-insoluble lignin (WIL) and water-soluble lignin (WSL) were obtained, accounting for 49.60 wt% and 38.00 wt% of the total lignin in raw bagasse, respectively. GG separated from the hydrolysate yielded an overall recovery of 68.17 wt% of the xylan from the raw bagasse. The relatively high yield of lignin and GG can be attributed to the incorporation of glycerol molecules. 2D HSQC NMR results revealed that glycerol effectively preserved the β-O-4 structure of lignin during ACG pretreatment through α-etherification and γ-esterification. 31P NMR results showed that WSL has more aliphatic hydroxyl groups, resulting in increased water solubility, whereas WIL exhibited a higher amount of phenolic hydroxyl groups, contributing to the increased in vitro antioxidant properties. WSL contained significant proportion of p-coumaric acid glycerides and demonstrated low cytotoxicity along with a favorable cellular antioxidant capacity (CAA). HPLC-MS analysis revealed that the GG was a mixture of 56.44% glyceryl xylosides and 36.49% glyceryl glucosides, which displayed a superior moisturising capacity compared to commercial humectants such as hyaluronic acid (HA) and α-glyceryl glucosides (αGG). Overall, this study establishes a foundation for the extraction of value-adding bioactive compounds from acid-catalysed glycerol pretreatment hydrolysate, supporting the implementation of ACG techniques in biorefineries.

Probing the relationship between chemical structure and thermal degradation behavior of acetone fractionated kraft lignin

This study reports the relationships between structure and thermal degradation behavior of industrial softwood and hardwood kraft lignin (KL) after acetone fractionation to obtain acetone soluble (AS) and acetone insoluble (AI) fractions with reduced structural polydispersity. The structure and thermal degradation behavior of AS-KL and AI-KL was examined by gel permeation chromatography, Fourier transform infrared, quantitative carbon-13 nuclear magnetic resonance spectroscopy, and thermogravimetric analysis. The results showed that the AS-KL fractions had reduced apparent molecular weight, lower polydispersity, less native wood lignin side chains, greater aromatic hydroxyl groups, and more condensed structures. In contrast, the AI-KL fractions showed substantially larger apparent molecular weight and polydispersity, as well as more aliphatic hydroxyl groups and native lignin side chains. Consequently, AI-KL samples exhibited greater thermal degradation activation energy than those of AS-KL samples because the former fractions had a larger apparent molecular weight as well as more aliphatic OH groups, which facilitated hydrogen bonding between lignin polymers, improving their thermal stability. This finding suggests that acetone fractionation of KL can be used to examine the relationship between structure and thermal degradation of industrial KL. These results also provide important information on the thermal degradation behavior of acetone fractionated products with relevant chemical and physical properties for a specific application, such as raw materials for lignin valorization.

A mild iodocyclohexane demethylation for highly enhancing antioxidant activity of lignin

Lignin, as a natural antioxidant, shows great potential in food engineering and medicine. However, the inherent macromolecular structure, high polydispersity, and few phenolic hydroxy seriously limit its antioxidant activity. In this work, a mild iodocyclohexane demethylation for highly improving the antioxidant activity of lignin was proposed. The results showed –OCH3 content exhibited an almost linear decrease as a function of treating time, and the demethylation and cleavage of β–aryl ether bonds prompt an obvious increase in phenolic hydroxyl content (4.01 mmol/g) and a significant decline in aliphatic hydroxyl (∼0.03 mmol/g). Meanwhile, attributing to the fragmentation of β–O–4, β–β, and β–5 substructures, the polydispersity of lignin molecular weight decreases from 2.7 to 2.2. As a result, the formed catechol-typed lignin showed an outstanding antioxidant activity, with the radical (DPPH·) scavenging index (inverse of concentration for 50% of maximal effect (EC50) value) over 2 000 mL/mg, much superior to the commercial antioxidants (< 500 mL/mg). Further structure-activity relationship analysis implied that the Ph–OH/–OCH3 ratio might act as a key factor influencing the antioxidant activity of lignin. This mild demethylation demonstrates a facile and effective method for highly enhancing the antioxidant activity of lignin and makes the catechol-typed lignin a green and promising product for practical use in food, medicine, and pharmacy.

SYNTHESIS OF SILVER NANOPARTICLES IN THE PRESENCE OF HYPERBRANCHED OLIGOMERIC IONIC LIQUID AS THEIR SURFACE STABILIZER

A method for synthesis of silver nanoparticles (AgNPs) in the presence of proposed by us protic anionic oligomeric ionic liquid (OIL) of hyperbranched structure as a stabilizer of their surface was developed. Reduction of Ag(I) silver cations was carried out with trisodium citrate in an aqueous environment at temperature of 100°C for an hour. The OIL proposed and used by us as a surface stabilizer of colloidal AgNPs is a product of exhaustive acylation of hyperbranched oligoester polyol of the 3rd generation (contains 32 terminal primary aliphatic hydroxyl groups) with cyclic 2-sulfobenzoic anhydride and subsequent neutralization of the resulting sulfonic compound with N-methylimidazole. The synthesized AgNPs stabilized with the OIL are powders soluble in water that opens up wide possibilities of using the developed AgNPs to obtain nanodisperse systems, in particular hydrosols and nanocomposite functional polymer materials. The formation of «guest-host» type complexes between the OIL and silver ions Ag(I) and the adsorption of carbonyl and ionic (their cationic component) groups on the surface of the formed AgNPs were established by FTIR. According to FTIR data trisodium citrate is also partially adsorbed on the surface of the formed silver nanoparticles and takes part in complex formation. The formation of AgNPs was also confirmed by X-ray analysis. The X-ray diffractograms of the obtained AgNPs show reflections at 38.0, 44.2, 64.4 and 77.3°, which are correspondingly related to (111), (200), (220) and (311) reflections of crystal planes and indicates the formation of silver nanoparticles with a face-centered cubic structure. It should be noted that the intensity of the above-mentioned reflexes increases with an increase in amount of the OIL used in the synthesis that confirms the stabilizing effect of the OIL in relation to the AgNPs and favoring the formation of the last ones due to autoreduction of silver. X-ray data evidences presence of trisodium citrate in the composition of the AgNPs being absorbed on the surface or as the complex with silver ions. The formation of AgNPs is also confirmed by TEM data. The TEM micrograph shows nanosized spherical particles of the «core-shell» type, where according to FTIR and X-ray analys a reduced silver is the core, and the OIL and trisodium citrate forms the shell as a stabilizer. These nanoparticles form swarm-like structures. Analysis of the microphotograph showed that the obtained AgNPs are characterized by a narrow size distribution in the range of 5–10 nm. The synthesized AgNPs stabilized with OIL and trisodium citrate are powders soluble in water, which opens up wide possibilities of their use for obtaining highly dispersed systems, in particular hydrosols and nanocomposite functional polymer materials based on them.

Beyond Yield Optimization: The Impact of Organosolv Process Parameters on Lignin Structure

AbstractWhen optimizing the process parameters of the acidic ethanolic organosolv process, the aim is usually to maximize the delignification and/or lignin purity. However, process parameters such as temperature, time, ethanol and catalyst concentration, respectively, can also be used to vary the structural properties of the obtained organosolv lignin, including the molecular weight and the ratio of aliphatic versus phenolic hydroxyl groups, among others. This review particularly focuses on these influencing factors and establishes a trend analysis between the variation of the process parameters and the effect on lignin structure. Especially when larger data sets are available, as for process temperature and time, correlations between the distribution of depolymerization and condensation reactions are found, which allow direct conclusions on the proportion of lignin's structural features, independent of the diversity of the biomass used. The newfound insights gained from this review can be used to tailor organosolv lignins isolated for a specific application.

Mannitol assisted oxalic acid pretreatment of poplar for the deconstruction and separation of hemicellulose

The effect of mannitol (MA) on the poplar separation using mannitol-assisted oxalic acid (M/OA) pretreatment was revealed. The effects of reaction parameters on the separation efficiency were studied. The optimized conditions were OA 7.0%, MA 7.0%, temperature 150 °C, and time 60 min. The hemicellulose separation was 79.08%. The separation of cellulose and lignin decreased from 12.43% and 21.82–8.58% and 16.11%, respectively, under hemicellulose separation similar to those of conventional OA pretreatment. Smooth fiber surfaces with less lignin deposition were observed. There were more β-O-4 and fewer β-β in lignin. Additionally, larger amounts of aliphatic hydroxyl groups and smaller amounts of phenolic hydroxyl groups were observed, which implies that MA addition prevented lignin from condensing. An effective and environmentally friendly separation of hemicellulose was achieved by M/OA pretreatment. This provides a practical approach for resolving the stubborn problems of lignin cleavage and condensation during organic acid pretreatment.

Designing Lignin-Based Biomaterials as Carriers of Bioactive Molecules.

There is a need to develop circular and sustainable economies by utilizing sustainable, green, and renewable resources in high-tech industrial fields especially in the pharmaceutical industry. In the last decade, many derivatives of food and agricultural waste have gained considerable attention due to their abundance, renewability, biocompatibility, environmental amiability, and remarkable biological features. Particularly, lignin, which has been used as a low-grade burning fuel in the past, recently attracted a lot of attention for biomedical applications because of its antioxidant, anti-UV, and antimicrobial properties. Moreover, lignin has abundant phenolic, aliphatic hydroxyl groups, and other chemically reactive sites, making it a desirable biomaterial for drug delivery applications. In this review, we provide an overview of designing different forms of lignin-based biomaterials, including hydrogels, cryogels, electrospun scaffolds, and three-dimensional (3D) printed structures and how they have been used for bioactive compound delivery. We highlight various design criteria and parameters that influence the properties of each type of lignin-based biomaterial and corelate them to various drug delivery applications. In addition, we provide a critical analysis, including the advantages and challenges encountered by each biomaterial fabrication strategy. Finally, we highlight the prospects and future directions associated with the application of lignin-based biomaterials in the pharmaceutical field. We expect that this review will cover the most recent and important developments in this field and serve as a steppingstone for the next generation of pharmaceutical research.

1-ethyl-3-methyl imidazolium acetate, hemicellulolytic enzymes and laccase-mediator system: Toward an integrated co-valorization of polysaccharides and lignin from Miscanthus

The pretreatment of Miscanthus x giganteus with the ionic liquid 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]), followed by enzymatic hydrolysis and oxidative depolymerization, resulted in the efficient production of monomeric sugars and selective production of phenolic intermediates. The liquid fractions containing monomeric sugars were obtained with high yields (>80%), while a solid fraction enriched with lignin (>50% w.w−1) was isolated. The phenolic monomers released during [Emim][OAc]-pretreatment were identified and quantified by HPLC. A decrease in the content of vanillin, vanillic acid, and p-hydroxybenzaldehyde was observed during pretreatment, suggesting a selective solubilization of guaicyl and p-hydroxyphenyl units from the lignin polymer in [Emim][OAc]. The decrease in p-coumaric and ferulic acids content suggested a cleavage of lignin-carbohydrate complexes during pretreatment. Both pretreatment and enzymatic hydrolysis affected the content of ferulic acid ether and ester bonds. The NMR structural study (2D HSQC) of the isolated lignin showed the preservation of β-O-4′ interunit bonds, while 31P NMR analysis revealed a high content of aliphatic hydroxyl groups. The oxidative depolymerization of the isolated lignin, catalyzed by the laccase mediator system in the presence of 5% v.v−1 recycled [Emim][OAc] in buffer, mainly led to the production of free p-hydroxybenzaldehyde as a promising platform molecule. The mass balance of glucan, xylan and lignin from Miscanthus was validated throughout this strategy.

Preparation and resource utilization of sludge-based fire-preventive and extinguishing composite gel for coal mine

We prepared a sludge-based fire-preventive and extinguishing composite gel for coal mines using sludge, HPAM, water glass, and sodium bicarbonate as the main raw materials. Orthogonal test was used to analyze the effects of each component and its level on the performance of gel to determine the optimal ratio of gel and then tested its fire-preventive and extinguishing characteristics. Finally, the gelling mechanisms of the gel are discussed. The composite gel prepared at the optimal level showed that the gelling time can be maintained at about 55 s, the water retention can reach up to 58.6% in 12 h at 100 °C. The gel has a dense microstructure and uniform pores, and has the best inhibition rate of coal spontaneous combustion. As compared with other materials, the coal piled with gel did not reignite. TGA showed that the gel hinders oxidation and complete combustion of coal. The in-situ infrared analysis confirmed that the coal sample treated with gel has a low content of aliphatic hydrocarbon and hydroxyl group. Infrared spectroscopy analysis indicated that the sludge in the gel plays the role of filler. The organic-inorganic composite network structure formed by the sludge and the gel not only prevents the system from water loss and coal oxidation but also absorbs a large amount of sludge and realizes the resource utilization of sludge. Therefore, the preparation of composite gel reduces the secondary pollution of sludge and lowers the cost of the material, making it an economical and environmentally friendly fire-preventive and extinguishing material.