Aging Resistance Evaluation of Aged Paper Reinforced with Different Nanocelluloses

Paper documents experience severe acidification and embrittlement.Nanocellulose is an excellent reinforcement material for paper documents owing to its compatibility and excellent mechanical strength.However,little research has been conducted on the aging resistance of nanocellulose-reinforced paper.In this study,six types of nanocelluloses were used to reinforce aged paper.The reinforcement and anti-aging performances were evaluated,and the anti-aging mechanism was further clarified.Nanocellulose with a high degree of polymerization can better enhance aged paper,and non-chemical nanocellulose also shows better anti-aging performance,such as nanocellulose prepared by mechanical or biological methods.However,nanocellulose prepared using chemical methods exhibits poor reinforcement and anti-aging performance.This is because it has a small particle size that is not beneficial for physical crosslinking with paper fibers.More importantly,the introduction of acidic or oxidizing groups on nanocellulose accelerates the acid hydrolysis and oxidation rate of paper fibers,especially nanocellulose prepared by 2,2,6,6-tetramethylpiperidine-1-oxyl oxidation,which should not be used to protect paper documents.

Dealuminated Hβ zeolite for selective conversion of fructose to furfural and formic acid

The fructose-to-furfural transformation is facing major challenges in the selectivity and high efficiency. Herein, we have developed a simple and effective approach for the selective conversion of fructose to furfural using Hβ zeolite modified by organic acids for dealuminization to regulate its textural and acidic properties. It was found that citric acid-dealuminized Hβ zeolite possessed high specific surface areas, wide channels and high Brønsted acid amount, which facilitated the selective conversion of fructose to furfural with a maximum yield of 76.2% at433 K for 1 h in the γ-butyrolactone(GBL)-H_(2)O system, as well as the concomitant formation of 83.0% formic acid. The^(13)C-isotope labelling experiments and the mechanism revealed that the selective cleavage of C1–C2 or C5–C6 bond on fructose was firstly occurred to form pentose or C5 intermediate by weak Brønsted acid, which was then dehydrated to furfural by strong Brønsted acid. Also this dealuminized Hβ catalyst showed the great recycling performance and was active for the conversion of glucose and mannose.

Bonding Plant Fibers with Uncondensed Lignin as Adhesive

The development of wood adhesives using biomass resources holds significant importance for sustainable resource utilization and public health.Utilizing non-condensed lignin directly as a wood adhesive provides a new approach for the green,low-cost,and large-scale production of high-performance wood adhesives.This innovation has the potential to drive the green and low-carbon development of the wood/plant products industry.

短链脂肪酸对糖尿病的调节机制及应用

膳食纤维(dietary fiber, DF)或抗性淀粉(resistant starch, RS)等益生元在肠道中被肠道细菌发酵,主要产物为短链脂肪酸(short-chain fatty acid, SCFAs)。短链脂肪酸可以通过多种途径对糖尿病产生有益的影响。肠道微生物群也与糖尿病发病机制密切相关,其在宿主免疫系统、饮食中的能量摄入以及人类基因表达的改变方面都起着至关重要的作用。本综述旨在总结肠道微生物群和短链脂肪酸在糖尿病中的作用来促进使用益生元和益生菌来预防和治疗这些代谢紊乱疾病综合策略的发展。

Co-Production of High-Grade Dissolving Pulp,Furfural,and Lignin from Eucalyptus via Extremely Low Acid Pretreatment and Pulping Technologies and Catalysis

Hemicellulose and lignin are not reasonably utilized during the dissolved pulp preparation process.This work aimed to propose a process for the co-production of dissolving pulp,furfural,and lignin from eucalyptus.High-grade dissolving pulp was prepared from eucalyptus using a combination of extremely low acid(ELA)pretreatment,Kraft cooking,and elementary chlorine-free(ECF)bleaching.The obtained pre-hydrolysate was catalytic conversion into furfural in a biphasic system,and lignin during Kraft cooking and ECF was recovered.The process condition was discussed as well as the mass flow direction.The results showed that ELA pretreatment could effectively remove 80.1%hemicellulose.Compared with traditional hydrothermal pretreatment,the ELA pretreatment significantly increased the xylose yield from 5.05 to 14.18 g/L at 170℃ for 2 h,which had practical significance for furfural production.The 82.7%furfural yield and 82.9%furfural selectivity were obtained from xylose-rich pre-hydrolysate using NaCl as a phase modifier in a biphasic system with 4-methyl-2-pentanone(MIBK)as an organic phase by ion exchange resin catalysts at 190℃ for 2 h.Subsequently,the pretreated eucalyptus was subjected to Kraft cooking,and the optimal alkali amount was 14%.Then,the Kraft pulp was bleached using the O-D1-EP-D_(2) sequence,and dissolving pulp was obtained with an ISO brightness of 86.0%,viscosity of 463 mL/g,andα-cellulose content of 95.4%.The Kraft lignin which has a potential application was investigated by 2D-HSQC NMR and 31P NMR.The results showed that the S/G ratio of Kraft lignin was 1.93,and the content of phenolic hydroxyl groups was 2.53 mmol/g.Moreover,based on the above proposed process,30.5 g dissolving pulp,5.5 g furfural,and 21.2 g lignin per 100 g eucalyptus chips(oven dry)were produced.This research will provide new catalysis and pulping technical routes for dissolving pulp,furfural,and Kraft lignin products,which are in great demand in the chemical industry.

Modification of Cellulose by Hydrophobic Long-chain Molecules: Advances and Prospects

Cellulose,a natural polymer material with abundant natural sources,is non-toxic,renewable,and biodegradable,making it one of the most promising green materials.Its inherent hydrophilicity dramatically limits the development and application of cellulose products.Hydrophobic modification can significantly change cellulose properties and endow it with additional functions depending on the types of modifying molecules.Controlled modification of cellulose by long-chain hydrophobic molecules is challenging.Significant advances took advantage of new reaction systems and copolymerization.This paper reviews recent innovations in long-chain cellulose hydrophobic modification.A brief value-adding assessment provides a reference for green changes of cellulose to make it fit for future applications.

Biochar-based Solid Acids as Catalysts for Carbohydrate Hydrolysis: A Critical Review

Recently, increasing interest has been focused on the hydrolysis of carbohydrates to monosaccharides, among which, glucose and xylose as typical platform sugars can be used to produce chemicals and biofuels. As heterogeneous catalysts, solid acids have gained extensive attention for biomass biorefinery and could replace the conventional process owing to their excellent properties, including acceptable acidity and easy separation. In particular, biochar-based solid acids derived from biomass are promising for biomass conversion owing to the low-cost of feedstocks and the simple preparation procedure. Herein, we attempt to provide a critical overview of biochar-based solid acids for hydrolysis of carbohydrates into glucose and xylose. The preparation methods and properties of biochar-based catalysts as well as the influence of their properties on catalytic performance were discussed in detail. We also highlight the major challenges facing the use of biochar-based solid acids for carbohydrate hydrolysis.

Triethylamine-catalyzed Isomerization of Glucose to Fructose under Low Temperature Conditions in Aqueous Phase

Isomerization of glucose derived from lignocellulosic biomass is an important step in biorefinery.Fructose isomerized from glucose,is used as a highly attractive sweetener in the food and beverages industries.However,the prevalence of side reactions at high glucose concentrations is a serious issue,leading to a significant reduction in the fructose yield,especially in the aqueous phase.In this study,an efficient method for the conversion of highly concentrated glucose into fructose under low temperature conditions using triethylamine as the catalyst was developed.It was demonstrated that high fructose yield could be maintained at high glucose concentration.At 60℃,fructose yield of 38.7%and fructose selectivity of 80.6%were achieved in 1 mol/L(approximately 17 wt%)glucose.When glucose concentration was increased to 2 mol/L(approximately 31 wt%),the fructose yield and selectivity were maintained at 34.7%and 77.4%,respectively.13C nuclear magnetic resonance(NMR)spectrometer was used to examine the glucose isomerization reaction.Compared to the NaOH catalytic system,triethylamine acted as a buffer to provide a stable alkaline environment for the catalytic system,further maintaining a high level of catalytic efficiency for the isomerization of glucose to fructose.

Role of UDP-Glucuronic Acid Decarboxylase in Xylan Biosynthesis in Arabidopsis

UDP-xylose （UDP-Xyl） is the Xyl donor used in the synthesis of major plant cell-wall polysaccharides such as xylan （as a backbone-chain monosaccharide） and xyloglucan （as a branching monosaccharide）. The biosynthesis of UDP-Xyl from UDP-glucuronic acid （UDP-GIcA） is irreversibly catalyzed by UDP- glucuronic acid decarboxylase （UXS）. Until now, little has been known about the physiological roles of UXS in plants. Here, we report that AtUXS1, AtUXS2, and AtUXS4 are located in the Golgi apparatus whereas AtUXS3, AtUXS5, and AtUXS6 are located in the cytosoh Although all six single AtUXS T-DNA mu- tants and the uxsl usx2 uxs4 triple mutant show no obvious phenotype, the uxs3 uxs5 uxs6 triple mutant has an irregular xylem phenotype. Monosaccharide analysis showed that Xyl levels decreased in uxs3 uxs5 uxs6 and linkage analysis confirmed that the xylan content in uxs3 xus5 uxs6 declined, indicating that UDP-Xyl from cytosol AtUXS participates in xylan synthesis. Gel-permeation chromatography showed that the molecular weight of non-cellulosic polysaccharides in the triple mutants, mainly composed of xylans, is lower than that in the wild type, suggesting an effect on the elongation of the xylan backbone. Upon saccharification treatment stems of the uxs3 uxs5 uxs6 triple mutants released monosaccharides with a higher efficiency than those of the wild type. Taken together, our results indicate that the cytosol UXS plays a more important role than the Golgi-localized UXS in xylan biosynthesis.