Solubilization and structural changes of lignin in naked oat stems during subcritical water autohydrolysis.

In this study, the solubilization and structural changes of lignin in naked oat stems were investigated under subcritical water autohydrolysis systems (170-210 °C, 0.68-1.85 MPa). In this system, Hemicellulose was preferentially hydrolyzed in the liquid water at elevated temperatures, leading to the production of acetic acid and glucuronic acid, which acidified the reaction system. Under acidic and high-temperature conditions, lignin primarily underwent degradation and condensation reactions. At autohydrolysis temperatures below 190 °C and autohydrolysis pressures below 1.22 MPa, lignin degradation was predominant, realizing a maximum lignin removal of 47.8 % and breakage of numerous ß-O-4 bonds from lignin. At autohydrolysis temperatures above 190 °C and autohydrolysis pressures above 1.22 MPa, lignin condensation dominated, with an increase in the amount of organic acids generated upon hemicellulose degradation, leading to condensation reactions with the degraded low-molecular-weight lignin. The degree of lignin condensation was positively correlated with the temperature of the reaction system. This study provides essential insights into the dynamic changes in the structure of lignin in both the hydrolysis residue and hydrolysis solution during subcritical water autohydrolysis.

Polymerized PEI-modified lignin polyphenolic materials by acid hydrolysis-phase separation for removal of Cr (VI) from industrial wastewater.

Cr (VI) accumulates in an aqueous environment and exhibits huge harm to human health and the ecological system. Developed lignin biomass materials are complicated to prepare and have limited properties, and advances in lignin phenolic modification are lacking. Herein, an aminated poplar lignin-pyrogallol (PLP-PEI) with a simple design and adjustable phenolic hydroxyl content was developed using the acid hydrolysis-phase separation (AH-PS) method, and modified by the atom transfer radical polymerization (ATRP) strategy. Through diverse characterization analysis, the structural changes of PLP-PEI in the step-by-step synthesis process were monitored. An effective biomass capture system (Bio-Cap) was shown via systematically investigating the adsorption behaviors of Cr (VI) on PLP-PEI under various environmental conditions. Benefiting from introducing phenolic hydroxyl and amino groups, PLP-PEI demonstrated efficient adsorption capacity (598.80 mg/g for Cr (VI)). Additionally, the material also exhibited advantages, including monomeric chemisorption properties, strong reduction capability, and stable regeneration properties. Multiple driving forces were involved in the capture and removal process of Cr (VI), including complexation and electrostatic interaction. The low-cost natural biomass resources supported the industrial-scale synthesis and practical application of advanced aminated lignin polyphenol material, which showed outstanding advantages and enormous potential in the field of water environmental restoration.

UV-blocking composite films containing hydrophilized spruce kraft lignin and nanocellulose: Fabrication and performance evaluation.

The development of biodegradable films with good UV-blocking and mechanical properties is of great significance for the alleviation of plastic pollution and the establishment of a sustainable society. Given that most natural biomass-derived films have poor mechanical and UV aging properties and are therefore of limited applicability, additives capable of mitigating these drawbacks are highly sought after. In particular, industrial alkali lignin, which is a byproduct of the pulp and paper industry, features a benzene ring-dominated structure with abundant active functional groups and is therefore a promising natural anti-UV additive and composite reinforcing agent. However, the commercial applications of alkali lignin are hindered by its structural complexity and polydispersity. Herein, spruce kraft lignin was fractionated and purified using acetone, subjected to structural characterization, and then quaternized based on the obtained structural data to increase water solubility. TEMPO-oxidized cellulose was supplemented with quaternized lignin at different loadings, and the mixtures were homogenized under high pressure to obtain uniform and stable lignin-containing nanocellulose dispersions, which were subsequently converted into films through suction filtration-based dewatering under pressure. The quaternization of lignin improved its compatibility with nanocellulose and endowed the corresponding composite films with excellent mechanical properties as well as high visible light transmission and UV-blocking performance. The film with a quaternized lignin loading of 6 % had UVA and UVB shielding efficiencies of 98.3 and 100 %, respectively, and featured a tensile strength (175.2 MPa) and elongation at break (7.6 %) that were 50.4 % and 72.7 % higher than those of the pure nanocellulose (CNF) film prepared under the same conditions, respectively. Thus, our work provides a cost-effective and viable method of preparing fully biomass-derived UV-blocking composite films.

Study on Dissociation and Chemical Structural Characteristics of Areca Nut Husk.

From the perspective of full-component utilization of woody fiber biomass resources, areca nut husk is an excellent woody fiber biomass feedstock because of its fast regeneration, significant regeneration ability, sustainability, low cost, and easy availability. In this study, fiber cell morphologies, chemical compositions, lignin structures, and carbohydrate contents of areca nut husks were analyzed and compared with those of rice straw, and the application potentials of these two materials as biomass resources were compared. We found that areca nut husk fibers were shorter and wider than those of rice straw; areca nut husk contained more lignin and less ash, as well as less holocellulose than rice straw; areca nut husk and rice straw lignin were obtained by ball milling and phase separation, and areca nut husk lignin was found to be a typical GHS-type lignin. Herein, the yield of lignocresol was higher than that of milled wood lignin for both raw materials, and the molecular size was more homogeneous. Tricin structural monomers were discovered in the lignin of areca nut husk, similar to those present in other types of herbaceous plants. Structures of areca nut husk MWL (AHMWL) and AHLC were comprehensively characterized by quantitative NMR techniques (that is, 1H NMR, 31P NMR, and 2D NMR). The molecular structure of AHLC was found to be closer to the linear structure with more functional groups exposed on the molecular surface, and the hydroxyl-rich p-cresol grafting structure was successfully introduced into the lignin structure. In addition, the carbohydrate content in the aqueous layer of the phase separation system was close to the carbohydrate content in the raw material, indicating that the phase separation method can precisely separate lignin from carbohydrates. These experimental results indicate that the phase separation method as a method for lignin utilization and structure study has outstanding advantages in lignin structure regulation and yield, and areca nut husk lignin is suitable for application in the same phase separation systems as short-period herbs, such as rice straw and wheat grass, and has the advantages of low ash content and high lignification degree, which will provide guidance for the high-value utilization of areca nut husk in the future.

Structural analysis of light-colored separated lignin (lignocresol) and its antioxidant properties.

The use of lignin is limited by its heterogeneity and complexity. This study was processed using different methods to obtain spruce milled wood lignin (SMWL), spruce kraft lignin (SKL), and spruce lignocresol (SLC) for comparative analysis of the structure and antioxidant activity. SMWL has a complete softwood lignin side-chains structure and lignin carbohydrate complexes. SKL contains fewer ether bonds, while more conjugate structures and condensed structures contribute to the color. However, the α-position of the lignin side chain eliminates most of the hydroxyl and ether bonds (ß-O-4/α-OH, phenylcoumaran, and dibenzodioxocine structure) and effectively grafts p-cresol in the phase separation reaction. It not only inhibits the self-condensation of lignin, but also forms the 1,1-diarylpropane unit while protecting ß-O-4 linkages from not breaking. Importantly, SLC has few conjugate structures that result in the lightest color among all lignin isolated. Besides, SLC has a high yield and contains trace carbohydrates, indicating that the phase separation method can achieve great amounts of purity separated lignin. The antioxidant activity of lignin was evaluated, results show that 85% of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals were scavenged at the end of 60 min. Owing to its unique color, structural properties, and continuous antioxidant activity, SLC has the potential to manufacture antioxidant cosmetics.

Lignin dissolution model in formic acid-acetic acid-water systems based on lignin chemical structure.

The separation of lignin from woody biomass and subsequent conversion into useful products requires a solution to the problem of its solubility. The expanded C9 formula of lignin, along with its atomic and functional groups, was determined by elemental analysis and NMRs spectroscopy. Based on the thus-obtained expanded C9 formula, the cohesion parameters of lignin dispersion (10.8-11.1 cal1/2·cm-3/2), polarity (4.15-4.31 cal1/2·cm-3/2), hydrogen bonding (6.30-7.38 cal1/2·cm-3/2), and solubility (13.2-14.0 cal1/2·cm-3/2) were respectively calculated using atomic and functional group contributions method. We established the relationship between lignin structure and lignin solubility parameters. The dissolution characteristics of wheat straw organic acid lignin, industrial eucalyptus kraft lignin, bamboo kraft lignin, and softwood kraft lignin in formic acid-H2O, acetic acid-H2O, and formic acid-acetic acid-H2O solvent systems were analyzed. The results indicate that the dissolution behavior of lignins follows the solubility parameters theory. We have developed a lignin dissolution model according to the lignin structure. This model obeys the solubility parameter theory, overcomes the limitations of the "like dissolves like" principle in organic acid-water systems, and provides a concise method for the selection of lignin solvent systems and the quantitative determination of their solvent composition.

Research Progress and Development Demand of Nanocellulose Reinforced Polymer Composites.

Nanocellulose is a type of nanomaterial with high strength, high specific surface area and high surface energy. Additionally, it is nontoxic, harmless, biocompatible and environmentally friendly and can be extracted from biomass resources. The surface groups of cellulose show high surface energy and binding activity on the nanoscale and can be modified by using various methods. Because nanocellulose has a high elastic modulus, rigidity and a low thermal expansion coefficient, it is an excellent material for polymer reinforcement. This paper summarizes the reinforcement mechanisms of nanocellulose polymer composites with a focus on the role of theoretical models in elucidating these mechanisms. Furthermore, the influence of various factors on the properties of nanocellulose reinforced polymer composites are discussed in combination with analyses and comparisons of specific research results in related fields. Finally, research focus and development directions for the design of high-performance nanocellulose reinforced polymer composites are proposed.

Adsorption of bovine serum albumin on the surfaces of poplar lignophenols.

Two phenolic compounds (p-cresol and pyrogallol) were introduced into the benzyl position of poplar lignin by a phase separation method to obtain lignin-based derivatives with different structural properties called poplar lignophenols (LPs). The maximum protein adsorption capacity of LPs is 50-70 times greater than that of the industrial lignin under the same conditions. The interaction between poplar LPs and bovine serum albumin (BSA) near its isoelectric point (pH = 4.5) was studied using a quartz crystal microbalance with dissipation monitoring (QCM-D). The adsorption and desorption of BSA molecules on different LPs were investigated at various pH values of the buffer solution (2.1, 6.4, and 10.0), and the interaction mechanism between LP and BSA species was examined. The obtained results showed that hydrogen bonding was the strongest binding force between LPs and BSA as compared with hydrophobic and electrostatic interactions. The findings of this work can help to establish a relationship between the contents of hydroxyl groups, molecular structures, and molecular sizes of LPs and proteins under different pH conditions.

Green biorefinery - the ultra-high hydrolysis rate and behavior of Populus tomentosa hemicellulose autohydrolysis under moderate subcritical water conditions.

A high monosaccharide conversion rate of hemicellulose in a green solvent and under moderate reaction conditions for industrialization is one of the most important keys in a lignocellulosic biorefinery. The behavior of Populus tomentosa hemicellulose polysaccharides, crystallinity and the furfural formation in the autohydrolysis process under moderate subcritical water conditions (160-180 °C, 0.618-1.002 MPa) were studied. The results have shown that the hemicellulose was converted to corresponding monosaccharides at an ultra-high hydrolysis rate. Factor analysis indicates that the temperature is the most important factor affecting hemicellulose autohydrolysis. When the autohydrolysis temperature increased from 160 to 180 °C for 2 h, the hydrolysis rate of xylose, rhamnose, galactose, mannose, and glucose from hemicellulose increased from 70% to 91%, 71% to 100%, 82% to 95%, 42% to 58%, and 34% to 37%, respectively. Arabinose was completely dissolved in 30 min. The xylose, rhamnose, galactose, and arabinose from hemicellulose could be almost completely removed under the conditions. The hemicellulose removal rate obtained herein exceeded the values reported for most acid, alkali, ionic liquid, or deep eutectic solvent treatments. It is notable that almost all glucose in hemicellulose was dissolved and the glucose in cellulose was partially hydrolyzed. An analysis of the sugar composition and the crystallinity change in the process at 180 °C demonstrate that hydrolysis reaction started to shift from amorphous regions to crystalline regions, due to the partial hydrolysis of crystalline cellulose after 90 min at 180 °C. Overall, these results show that the moderate subcritical water autohydrolysis of hemicellulose in Populus tomentosa may be a potential bio-refinery process.

Correction: Research status, industrial application demand and prospects of phenolic resin.

[This corrects the article DOI: 10.1039/C9RA06487G.].

Distal pancreatectomy with en bloc celiac axis resection does not improve the R0 rate or median survival time of patients with locally advanced pancreatic cancer: a systematic review and meta-analysis.

BACKGROUND: Pancreatic cancer frequently results in celiac artery invasion, resulting in an unresectable disease that generally has a median survival period of 6-11 months. Efforts to achieve curative resection of such tumors have been made by conducting distal pancreatectomy with en bloc celiac axis resection (DP-CAR) in some patients, but the long-term outcome data associated with this approach or its overall value remain to be clarified. METHODS: This meta-analysis was conducted to systematically assess the clinical efficacy of the DP-CAR treatment of unresectable tumors of the pancreatic body or tail (registered with PROSPERO: CRD42019129612). The PubMed, EMBASE, the Cochrane Library, and Web of Science databases were searched to identify relevant retrospective studies pertaining to such treatment. RESULTS: Overall, 12 retrospective cohort analyses incorporating 213 total DP-CAR cases and 911 DP cases were incorporated into the present meta-analysis. Pooled analyses demonstrated that relative to DP, DP-CAR was related to a longer operative duration [mean difference (MD) -73.69, 95% confidence interval (CI): -112.99 to -34.38, P=0.0002] and higher blood transfusion rates [odds ratio (OR) 0.29, 95% CI: 0.10 to 0.87; P=0.03]. DP-CAR was also linked to increased rates of PV resection (OR 0.17, 95% CI: 0.07 to 0.39; P<0.001) and delayed gastric emptying (DGE) (OR 0.37, 95% CI: 0.15 to 0.93, P=0.03). In contrast, R0 resection rates were higher in the DP group (OR 2.79, 95% CI: 1.90 to 4.09, P<0.001), and these patients also had a significantly improved prognosis (median survival time, 27.0 vs. 17.7 months; P<0.01) relative to the DP-CAR group. CONCLUSIONS: This analysis indicates that DP-CAR is not an effective means of improving R0 rates. However, available studies suggest that it is nonetheless a potentially valuable treatment option for pancreatic cancer patients with celiac axis involvement, and it is associated with a reasonable median survival duration of 17.7 months.

Mortality from heart disease following radiotherapy in esophageal carcinoma: a retrospective cohort study in US SEER cancer registry.

BACKGROUND: Recently, multiple studies have focused on cardiac toxicity induced by radiation, particularly in patients with breast carcinoma. However, in most circumstances, the radiation intensity is much higher for the heart in patients with esophageal carcinoma. This study aimed to investigate whether cardiac toxicity is related to radiation and distinguish the types of patients who are more susceptible to cardiac death. METHODS: We analyzed 8,210 esophageal cancer survivors who were involved in the US Surveillance Epidemiology and End Results (SEER) cancer program. Descriptive statistics were used to demonstrate the disease characteristics in radiation therapy (RT) and non-RT groups. Cox hazard proportional regression and Kaplan-Meier method were applied to determine independent risk factors of cardiac death. RESULTS: The most important risk factors determining heart death were age (HR, 14.297; 95% CI: 9.174-22.283) and radiation (HR, 1.952; 95% CI: 1.684-2.263). The radiotherapy performed in the middle (HR, 1.872; 95% CI: 1.464-2.395) and lower thoracic segment of the esophagus (HR, 1.539; 95% CI: 1.464-1.772) was associated with an increased risk of cardiogenic death, which occurred since the first year after diagnosis. Compared with RT in postoperative group (HR, 0.48; 95% CI, 0.37-0.62), patients in preoperative group had a significantly increased survival rate. CONCLUSIONS: Cardiogenic death is closely related to RT in esophageal cancer patients. Age, radiation sequence and tumor sites are key factors influencing the cardiac death risk induced by radiotherapy. Early detection and prevention are necessary for the high-risk population.

Worse characteristics can predict survival effectively in bilateral primary breast cancer: A competing risk nomogram using the SEER database.

OBJECTIVE: There is limited information from population-based cancer registries regarding prognostic features of bilateral primary breast cancer (BPBC). METHODS: Female patients diagnosed with BPBC between 2004 and 2014 were randomly divided into training (n = 7740) and validation (n = 2579) cohorts from the Surveillance, Epidemiology, and End Results Database. We proposed five various models. Multivariate Cox hazard regression and competing risk analysis were to explore prognosis factors in training cohort. Competing risk nomograms were constructed to combine significant prognostic factors to predict the 3-year and the 5-year survival of patients with BPBC. At last, in the validation cohort, the new score performance was evaluated with respect to the area under curve, concordance index, net reclassification index and calibration curve. RESULTS: We found out that age, interval time, lymph nodes invasion, tumor size, tumor grade and estrogen receptor status were independent prognostic factors in both multivariate Cox hazard regression analysis and competing risk analysis. Concordance index in the model of the worse characteristics was 0.816 (95% CI: 0.791-0.840), of the bilateral tumors was 0.819 (95% CI: 0.793-0.844), of the worse tumor was 0.807 (0.782-0.832), of the first tumor was 0.744 (0.728-0.763) and of the second tumor was 0.778 (0.762-0.794). Net reclassification index of the 3-year and the 5-year between them was 2.7% and -1.0%. The calibration curves showed high concordance between the nomogram prediction and actual observation. CONCLUSION: The prognosis of BPBC depended on bilateral tumors. The competing risk nomogram of the model of the worse characteristics may help clinicians predict survival simply and effectively. Metachronous bilateral breast cancer presented poorer survival than synchronous bilateral breast cancer.

Pancreatic neuroendocrine tumours: Grade is superior to T, N, or M status in predicting outcome and selecting patients for chemotherapy:A retrospective cohort study in the SEER database.

BACKGROUND: Pancreatic neuroendocrine tumours (pNETs) are a rare and heterogeneous group of tumours with an increasing incidence. Current staging criteria for pNETs remain limited and controversial. Meanwhile, the impact of chemotherapy on overall survival has not been fully defined. OBJECTIVES: The current study aimed to explore epidemiologic trends of pancreatic neuroendocrine tumours (pNETs). To determine feasible improvements to staging criteria and investigate the relationship between chemotherapy and survival. METHODS: A retrospective cohort study design was used to analyse annual cancer incidence rates, patient demographics, tumour site and stage, and treatment of pNETs. Data were obtained from the National Cancer Institute's SEER registry for all patients diagnosed with pNETs between January 1973 and December 2015. RESULTS: Patients diagnosed after 2010 were more likely to present with age greater than 45 years, T0, T1 status, N0 status, M0 status, and well differentiation. Current AJCC staging criteria was applicable to patients with well differentiation, but not other differentiation. The revised system, defined by Grade, T, N, and M status, could robustly discriminate between survival curves. Chemotherapy was associated with significantly improved survival for patients with poorly differentiated and undifferentiated tumour grading. CONCLUSIONS: Grade is superior to 'T', 'N', or 'M' status in predicting outcomes and selecting patients for chemotherapy. It is necessary and feasible to combine grade into current staging criteria.

Changes in chemical structures of wheat straw auto-hydrolysis lignin by 3-hydroxyanthranilic acid as a laccase mediator.

3-Hydroxyanthranilic acid (3-HAA), as a potential natural laccase mediator, was shown to mediate the oxidation of non-phenolic lignin subunits. The problem of cost and toxicity of artificial mediators could be solved to some extent by a further study about the detailed changes of lignin chemistry structures in laccase 3-HAA system (LHS). In this work, wheat straw auto-hydrolysis lignin (AL) was prepared. Oxidations of AL by LHS and laccase 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) system were then investigated, respectively. Various structural changes of AL during the oxidation were characterized by different methods including phenolic hydroxyl group determination, nitrobenzene oxidation, ozonation, gel permeation chromatography, ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy and two-dimensional nuclear magnetic resonance (2D NMR) spectroscopy. The changes in AL chemical structures were found in LHS, including unit removal, bond cleavage and biopolymerization. Compared to laccase ABTS system, a selective removal of guaiacyl-type lignin in LHS was observed, based on the results of nitrobenzene oxidation and 2D NMR analysis. The selective removal of guaiacyl-type lignin was due to improved aromatic ring cleavage and weaken lignin biopolymerization. The selectivity of guaiacyl-type lignin removal in LHS plays an important role, especially for improving bioconversion efficiency of laccase for guaiacyl-rich lignocellulosic biomass.

Research status, industrial application demand and prospects of phenolic resin.

The synthesis process of the phenolic resin adhesive was developed in the 19th century, and its excellent environmental resistance and high bonding strength make it one of the main wood adhesives. With the development of industry, phenolic resin adhesive is not only used in plywood, wood processing and laminate, but also in automobile, aerospace, composite materials and other fields. Herein we review the main synthetic processes and latest research progress for phenolic resin adhesives, the capacity distribution of major domestic phenolic resin enterprises, analysis of domestic phenolic resin consumption, import and export volume and price, Chinese plywood production, and the main production and export markets. Furthermore, research and discussion on the commercial application of domestic phenolic resin adhesives in plywood were carried out, which provides a reference for development of better phenolic resin adhesives that meet the development needs of the country, along with quality and economic competitiveness.

Structural Characterization of Lignocresols from Transgenic and Wild-Type Switchgrass.

Cafferic acid-O-methyltransferases (COMT) down-regulated transgenic and wild-type switchgrass were separated into lignocresols (LCs) and sugars by a phase separation method involving 72% sulfuric acid and cresol. The isolated LCs were characterized by FTIR, GPC, ¹H NMR and 2D-HSQC to understand potential structural modification caused by transgenic engineering lignin or phase separation treatment. No significant changes were found in terms of molecular weights and the amount of incorporated p-cresols between transgenic and wild-type switchgrass LCs. However, the compositions, ratios of syringyl (S) units to guaiacyl (G) units, were changed significantly leading to decrease in S units and increase in G units for transgenic switchgrass LC. The benzodioxane structures and 5-hydroxyguaiacyl units were observed in the 2D-HSQC implied that 5-hydroxyconiferyl alcohol was incorporated into lignin as a result of COMT-down-regulation in the transgenic process.

Influence of TEMPO-mediated oxidation on the lignin of thermomechanical pulp.

The influences of various factors in 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation on delignification, lignin aromatic ring and side chain structures of thermomechanical pulp (TMP) were investigated. The results indicate neither TEMPO nor NaBr alone can provoke changes in lignin content or lignin structure under weakly alkaline conditions. However, NaClO and NaClO-NaBr were able to remove lignin effectively, causing remarkable changes in lignin structure. Delignification was promoted when TEMPO was used with NaBr and NaClO. In contrast to NaClO alone, an additional 15% lignin was removed when TEMPO-mediated oxidation system was used, but it did not induce further changes on lignin structure. Increased doses of oxidizing agent and reaction time also improved the oxidation of cellulose and delignification, but they did not have a significant impact on lignin aromatic and side chain structures.

[Synthesis and spectroscopic study of polyamine-type cellulose-based chelating fiber].

The graft copolymer (CPGMA) made from bleached chemical eucalyptus pulp (BCEP) and glycidyl methacrylate (GMA) was reacted with ethylenediamine (EDA) to synthesize the polyamine-type cellulose-based chelating fiber CPGMA-EDA. The chelating fiber was characterized by means of Fourier transform infrared spectroscopy (FTIR), 13C cross polarization magic angle spinning NMR spectra (13C CP/MAS NMR) and X-ray diffraction (XRD). The results of FTIR and 13C CP/MAS NMR show that the characteristic absorption peak (904 cm(-1) of epoxy group in CPGMA disappeared, and the absorption peak around 3 200-3 500 cm(-1) broadened due to the vibration of new formed N-H bond while the CPGMA reacted with EDA. Both of these indicate that amino group was grafted onto CPGMA through the ring-opening reaction. The XRD results indicate that the crystallinity of CPGMA-EDA was 48.1%, and decreased by 31.1% compared to that of BECP, indicating that the reaction not only takes place in the noncrystal regions, but also in the crystal regions of cellulose.