Tuning structure of spent coffee ground lignin by temperature fractionation to improve lignin-based carbon nanofibers mechanical performance.

Fabricating lignin-based carbon nanofibers (LCNFs) with the lignin in spent coffee grounds (SCG) as raw material which are disposed as waste amounting to millions tons annual is benefit to promote economy and environmental protection. However, due to the heterogeneity and complex three-dimensional structure, the mechanic property is very poor. In this study, we propose a fractionating pretreatment method to overcome the above problems by regulating the structure of SCG lignin in which high-performance LCNFs were fabricated. On one hand, the linear structure of SCG lignin was optimized to fit the raw material of LCNFs by tuning the content of ß-O-4 and C5-substituted condensed phenolic compounds. On the other hand, the carboxyl as the hydrophilic groups was removed so as to promote the mixing of lignin and polyacrylonitrile (PAN, blending agent) in organic solvents. Additionally, the heterogeneity was reduced by screening large molecular weight SCG lignin with low polydispersity index (PDI). Fortunately, with 1:1 mass ratio of the above fractionated lignin and PAN as substrate, the LCNFs could reach to comparable mechanic properties with those of pure PAN CNFs. This work can provide a new way to not only promote the utilization of SCG lignin but also accelerate the development of LCNFs.

Structural elucidation of lignin macromolecule from abaca during alkaline hydrogen peroxide delignification.

To maximize the utilization of Abaca lignin in the current biorefinery, structural characteristics of native lignin from Abaca were firstly comprehensively investigated. Parallelly, effective delignification of Abaca was achieved by alkaline hydrogen peroxide (AHP) process, which facilitated the production of specialty paper in industry. The structural changes of lignin macromolecules during the AHP delignification were illustrated by comparing the structural differences of the released lignin fraction and corresponding native lignin, which were analyzed via the advanced analytical methods, such as 2D-HSQC NMR, 31P NMR, pyrolysis-GC/MS, and GPC techniques. It was found that Abaca lignin is a HGS-type lignin, which is overwhelmingly composed of ß-O-4 linkages and abundant hydroxycinnamic acids (mainly p-coumaric acid). In addition, partial cleavage of ß-O-4 linkages and p-coumarate in lignin occurred during the AHP delignification process. Meanwhile, AHP process also led to the elevation of H-type lignin units in AHPL. Considering that ß-O-4 bond is vulnerable in the catalytic degradation process of lignin, the lignin with abundant ß-O-4 linkages is beneficial to the downstream conversion of lignin into aromatic chemicals.

Structural Features of Alkaline Dioxane Lignin and Residual Lignin from Eucalyptus grandis × E. urophylla.

In the present study, lignin from eucalyptus was extracted with 80% alkaline dioxane (0.05 M NaOH) from ball-milled wood and subsequently fractionated by gradient acid precipitation from the filtrate. Meanwhile, the residual lignin was prepared by a double enzymatic hydrolysis process. The yield of the lignin extracted by alkaline dioxane (LA-2) was 29.5%. The carbohydrate contents and molecular weights of the gradient acid precipitated lignin fractions gradually decreased from 4.90 to 1.36% and from 7770 to 5510 g/mol, respectively, with the decline of the pH value from 6 to 2. Results from two-dimensional heteronuclear single quantum coherence nuclear magnetic resonance (NMR) and 31P NMR spectroscopy showed an evident reduction of ß- O-4 ' linkages with the pH value decrease, while the contents of aliphatic -OH, phenolic -OH, and carboxylic groups displayed an increasing trend. Moreover, the residual lignin exhibited the highest molecular weight (11690 g/mol), the most abundant ß- O-4 ' linkages (71.1%), and the highest S/G ratio (4.68).

Eucommia ulmoides Oliver: A Potential Feedstock for Bioactive Products.

Eucommia ulmoides Oliver (EUO), a traditional Chinese herb, contains a variety of bioactive chemicals, including lignans, iridoids, phenolics, steroids, terpenoids, flavonoids, etc. These bioactive chemicals possess the effective function in nourishing the liver and kidneys and regulating blood pressure. The composition of bioactive chemicals extracted from EUO vary in the different functional parts (leaves, seeds, bark, and staminate flower) and planting models. The bioactive parts of EUO are widely used as raw materials for medicine and food, powdery extracts, herbal formulations, and tinctures. These capabilities hold potential for future development and commercial exploitation of the bioactive products from EUO.

Structural characterization of hemicelluloses and topochemical changes in Eucalyptus cell wall during alkali ethanol treatment.

Eucalyptus was sequentially extracted with 70% ethanol containing 0.4, 1.0, 2.0, 3.0, and 5.0% NaOH for 2h at 80°C. The chemical composition and structural features of the hemicellulosic fractions obtained were comparatively characterized by the combination of high-performance anion-exchange chromatography, gel permeation chromatography, Fourier transform infrared, and nuclear magnetic resonance spectroscopies. Furthermore, the main component distribution and their changes in cell wall were investigated by confocal Raman microscopy. Based on the Fourier transform infrared and nuclear magnetic resonance analyses, the hemicelluloses extracted from Eucalyptus mainly have a linear backbone of (1→4)-linked-ß-d-xylopyranosyl residues decorated with branch at O-2 of 4-O-methyl-α-glucuronic acid unit. Raman analysis revealed that the dissolution of hemicelluloses was different in the morphological regions, and the hemicelluloses released mainly originated from the secondary wall. The information obtained from the study conducted by combining chemical characterization with ultrastructure provides important basis for studying the mechanism of the alkali treatment.

Integrated biorefinery based on hydrothermal and alkaline treatments: investigation of sorghum hemicelluloses.

An integrated process based on hydrothermal pretreatment (HTP) and alkaline post-treatment was proposed to treat sweet sorghum stem. The structural features of the alkali-soluble hemicelluloses (ASHs) obtained from the un-pretreated and hydrothermally pretreated materials were comprehensively investigated by HPAEC, GPC, NMR, FT-IR, and TGA techniques. The ASH with the highest yield (60.6%) was obtained from the HTP residue performed at 130 °C for 1.0 h. All the results indicated that the ASHs had a more linear structure with increasing the pretreatment temperature (110-170 °C). The molecular weights of the ASHs were decreased with increasing the pretreatment temperature, suggesting that C-O bonds in the ASHs were gradually cleaved, especially at the higher temperatures (≥ 170 °C). Interestingly, the integrated process yielded more homogeneous ASHs than hemicelluloses obtained from the un-pretreated material. Based on the spectral analyses, the structure of the ASHs was assumed to be L-arabino-4-O-methyl-D-glucurono-D-xylan.

Structural features and antioxidant activities of lignins from steam-exploded bamboo (Phyllostachys pubescens).

An environmentally friendly steam explosion process of bamboo, followed by alkali and alkaline ethanol delignification, was developed to fractionate lignins. Results showed that after steam explosion the lignins isolated showed relatively low carbohydrate contents (0.55-1.76%) and molecular weights (780-1050 g/mol). For each steam-exploded sample, alkali-extracted lignins presented higher phenolic OH values (1.41-1.82 mmol/g), p-coumaric acid to ferulic acid ratios (pCA/FA ratios 4.5-14.1), and syringyl to guaiacyl ratios (S/G ratios 5.0-8.5) than those from alkaline ethanol-extracted lignins (phenolic OH 0.85-1.35 mmol/g, pCA/FA ratios 1.6-5.2, and S/G ratios 3.5-4.8). The lignins obtained consisted mainly of ß-O-4' linkages combined with small amounts of ß-ß', ß-5', and α-O-4/ß-O-4 linkages. Antioxidant activities of the lignins obtained were tested by the 2,2-diphenyl-1-picrylhydrazyl, 2,2'-azobis(3-ethylbenzothiazoline-6-sulfonic acid), and ferric reducing activity power methods. It was found that alkali-extracted lignins obtained during the initial extraction process had higher antioxidant activities than alkaline ethanol-extracted lignins obtained during the second extraction process.

Microwave-assisted acid hydrolysis to produce xylooligosaccharides from sugarcane bagasse hemicelluloses.

Hemicelluloses from sugarcane bagasse were subjected to microwave-assisted acid hydrolysis at mild temperature to produce xylooligosaccharides (XOS). The hydrolysis was performed with dilute H2SO4 at 90°C and the influence of acid concentration (0.1-0.3M) and reaction time (20-40min) on the XOS production was ascertained with response surface methodology based on central composite design. The fitted models of XOS and xylose yields were in good agreement with the experimental results. Compared to hydrolysis time, acid concentration was a more significant coefficient in the production of XOS. A well-defined degree of polymerisation of XOS and the monomer in the hydrolysates were quantified. No sugar-degraded byproduct was detected. The maximum XOS yield of 290.2mgg(-1) was achieved by hydrolysis with 0.24M H2SO4 for 31min. The results indicated that the yields of xylose and the byproducts can be controlled by the acid concentration and reaction time in microwave-assisted acid hydrolysis.

Hydrothermal liquefaction of cornstalk: 7-lump distribution and characterization of products.

Hydrothermal liquefaction of cornstalk at 180-300 °C at ratios of water to cornstalk of 6-14 was conducted, and the reaction products were lumped into gas, water-soluble organics (ethanol-insoluble and ethanol-soluble organics), heavy oil, volatile organic compounds, and acid-soluble and acid-insoluble solid residues. Low temperature, high ratio of water to cornstalk, and short reaction time favored the formation of bio-oil (ethanol-insoluble organics, ethanol-soluble organics, and heavy oil) but inhibited the formation of acid-insoluble solid residue. Increasing temperature and reaction time increased the yields of gas and volatile organic compounds, whereas decreased the yield of acid-soluble solid residue. Bio-oil yields increased first and then decreased at a ratio of water to cornstalk higher than 10. Overall, the studied reaction parameters influenced the conversion among the lumps and product properties. This study suggests that lump analysis provides a promising approach to describe the product distributions in biomass liquefaction.

Separation and characterization of acetyl and non-acetyl hemicelluloses of Arundo donax by ammonium sulfate precipitation.

Delignified Arundo donax was sequentially extracted with DMSO, saturated barium hydroxide, and 1.0 M aqueous NaOH solution. The yields of the soluble fractions were 10.2, 6.7, and 10.0% (w/w), respectively, of the dry Arundo donax materials. The DMSO-, Ba(OH)(2)- and NaOH-soluble hemicellulosic fractions were further fractionated into two subfractions by gradient 50% and 80% saturation ammonium sulfate precipitation, respectively. Monosaccharide, molecular weight, FT-IR, and 1D ((1)H and (13)C) and 2D (HSQC) NMR analysis revealed the differences in structural characteristics and physicochemical properties among the subfractions. The subfractions precipitated with 50% saturation ammonium sulfate had lower arabinose/xylose and glucuronic acid/xylose ratios but had higher molecular weight than those of the subfractions precipitated by 80% saturation ammonium sulfate. FT-IR and NMR analysis revealed that the highly acetylated DMSO-soluble hemicellulosic subfraction (H(D50)) could be precipitated with a relatively lower concentration of 50% saturated ammonium sulfate, and thus the gradient ammonium sulfate precipitation technique could discriminate acetyl and non-acetyl hemicelluloses. It was found that the DMSO-soluble subfraction H(D50) precipitated by 50% saturated ammonium sulfate mainly consisted of poorly substituted O-acetyl arabino-4-O-methylglucurono xylan with terminal units of arabinose linked on position 3 of xylose, 4-O-methylglucuronic acid residues linked on position 2 of the xylan bone, and the acetyl groups (degree of acetylation, 37%) linked on position 2 or 3. The DMSO-soluble subfraction H(D80) precipitated by 80% saturated ammonium sulfate was mainly composed of highly substituted arabino-4-O-methylglucurono xylan and ß-d-glucan.

Microwave-assisted organic acid extraction of lignin from bamboo: structure and antioxidant activity investigation.

Microwave-assisted extraction in organic acid aqueous solution (formic acid/acetic acid/water, 3/5/2, v/v/v) was applied to isolate lignin from bamboo. Additionally, the structural features of the extracted lignins were thoroughly investigated in terms of C9 formula, molecular weight distribution, FT-IR, (1)H NMR and HSQC spectroscopy. It was found that with an increase in the severity of microwave-assisted extraction, there was an increase of phenolic hydroxyl content in the lignin. In addition, an increase of the severity resulted in a decrease of the bound carbohydrate content as well as molecular weight of the lignin. Antioxidant activity investigation indicated that the radical scavenging index of the extracted lignins (0.35-1.15) was higher than that of BHT (0.29) but lower than that of BHA (3.85). The results suggested that microwave-assisted organic acid extraction provides a promising way to prepare lignin from bamboo with good antioxidant activity for potential application in the food industry.

Microwave-induced synthesis of carboxymethyl hemicelluloses and their rheological properties.

In this article, a facile, rapid, and efficient method was developed for the preparation of carboxymethyl hemicelluloses using microwave-induced organic reaction enhancement chemistry. The influences of the factors including reaction time, temperature, and the amount of sodium monochloroacetate and sodium hydroxide on the degree of substitution (DS) of the products were investigated. The rheological properties and the chemical structure of the resulting polymers were also studied. It was found that microwave irradiation could significantly promote the chemical reaction efficiency and accelerate the carboxymethylation of hemicelluloses with sodium monochloroacetate. Therefore, carboxymethyl hemicelluloses with higher DS of 1.02 could be obtained in much shorter time scales as compared to the conventional heating method. Results from rheological analysis indicated that carboxymethyl hemicellulose solutions exhibited shear-thinning behavior in the range of shear rates tested and showed lower viscosity and modulus in comparison with those of the native hemicelluloses due to lower molecular weight and the role of carboxymethyl groups in reducing the entanglements between hemicelluloses chains.

Isolation and characterization of lignins from Eucalyptus tereticornis (12ABL).

A three-step sequential extraction-precipitation method was used to isolate lignin from Eucalyptus tereticornis. The ball-milled eucalyptus was extracted with 96% dioxane, 50% dioxane, and 80% dioxane containing 1% NaOH at boiling temperature, consecutively resulting in solubilization of lignin and hemicelluloses. By precipitating such solutions into 70% aqueous ethanol, the hemicelluloses were removed substantially although there were still some carbohydrates left over, especially for lignin fraction extracted by 50% dioxane. Lignins dissolved in the 70% ethanol solutions were recovered via concentration and precipitation into acidified water. About 37% of the original lignin was released following such procedure whereas only 13.5% can be isolated by traditional milled wood lignin (MWL) method. The obtained lignin fractions were analyzed by high performance anion exchange chromatography (HPAEC) following acid hydrolysis for sugar composition of the contaminating carbohydrates and characterized by quantitative (31)P NMR as well as two-dimensional heteronuclear single-quantum coherence ((13)C-(1)H) NMR. The results showed that 96% aqueous dioxane extraction of ball-milled wood under conditions used in this study resulted in lignin preparation with very similar structures and sugar composition as traditional MWL. Therefore extracting ball-milled wood with 96% aqueous dioxane produced lignin in 33.6% yield, which makes it very attractive as an alternative to the traditional MWL method. However further extraction with 50% aqueous dioxane or 80% aqueous dioxane containing 1% NaOH gave just a little more lignins with different carbohydrate compositions from those in MWL. The eucalyptus lignins obtained were syringyl and guaiacyl type units. Lignin fraction obtained from 96% dioxane extraction was found to have more phenolic hydroxyl and less aliphatic hydroxyl than the other two preparations.

Fractional isolation and chemical structure of hemicellulosic polymers obtained from Bambusa rigida species.

Water and aqueous alkali sequential treatments of delignified bamboo particles were performed to extract hemicelluloses with a high yield and weight-average molecular mass (Mw). The sequential treatment together dissolved 42% of hemicelluloses based on dry holocellulose. GPC results showed that the alkali-extractable hemicelluloses have higher Mw (35000 and 44450 g mol(-1)) than water-extractable ones (20100-28100 g mol(-1)). Structural determination based on FT-IR and (1)H, (13)C, and 2D-HSQC NMR analyses showed that both the water- and alkali-extractable hemicelluloses shared the structure composed of the (1 → 4)-linked ß-D-xylopyranosyl backbone with 4-O-methyl-α-d-glucuronic acid attached to O-2 of the xylose residues and l-arabinose attached to O-3 of the xylose residues. Moreover, it revealed that the water-extractable hemicelluloses retained original structure without cleaving chemical linkages. Furthermore, it was also found that the hemicelluloses with the highest yield and Mw were obtained by the aqueous alkali treatment from the delignified bamboo. A small amount of other minor hemicelluloses (ß-glucans) including xylans in the water-extractable hemicelluloses could be identified by NMR and other approaches.

Fractional study of alkali-soluble hemicelluloses obtained by graded ethanol precipitation from sugar cane bagasse.

The two hemicellulosic fractions were subsequentially extracted with 5% and 8% NaOH aqueous solution at a solid to liquid ratio of 1:25 (g mL(-1)) at 50 degrees C for 3 h from the water, 1 and 3% NaOH-treated sugar cane bagasse, and subfractionated into six preparations by a graded ethanol precipitation method at concentrations of 15%, 30% and 60% (v/v). Sugar composition and molecular weight analysis showed that, with an increasing concentration of ethanol, hemicellulosic subfractions with both higher Ara/Xyl ratios and higher molecular weights were obtained. In other words, with an increasing ethanol concentration from 15% to 60%, the Ara/Xyl ratios increased from 0.043 in H(1) to 0.088 in H(3) and from 0.040 in H(4) to 0.088 in H(6), and the weight-average molecular weights of hemicellulosic subfractions increased from 42 430 (H(1)) to 85 510 (H(3)) g mol(-1) and from 46 130 (H(4)) to 64 070 (H(6)) g mol(-1), respectively. The results obtained by the analysis of Fourier transform infrared, sugar composition, and (1)H and (13)C nuclear magnetic spectroscopy showed that the alkali-soluble hemicelluloses had a backbone of xylose residues with a beta-(1-->4)-linkage and were branched mainly through arabinofuranosyl units at C-2 and/or C-3 of the main chain, whereas the differences may occur in the distribution of branches along the xylan backbone.

Studies on the preparation of biodiesel from Zanthoxylum bungeanum Maxim seed oil.

To reduce the cost of biodiesel production, the feasibility of Zanthoxylum bungeanum Maxim seed oil (ZBMSO) was studied to produce biodiesel. A methyl ester biodiesel was produced from ZBMSO using methanol, sulfuric acid, and potassium hydroxide in a two-stage process. The main variables that affect the process were investigated. The high level of free fatty acids in ZBMSO was reduced to < 1% by an acid-catalyzed (2% H2SO4) esterification with methanol to oil molar ratios of 20-25:1 for 1 h. A maximum yield of 96% of methyl esters in ZBMSO biodiesel was achieved using a 6.5:1 molar ratio of methanol to oil, 0.9% KOH (percent oil), and reaction time of 0.5 h at 55 degrees C. Further investigation has also been devoted to the assessment of some important fuel properties of ZBMSO biodiesel produced under the optimized conditions according to specifications for biodiesel as fuel in diesel engines. The fuel properties of the ZBMSO biodiesel obtained are similar to those of no. 0 petroleum diesel fuel, and most of the parameters comply with the limits established by specifications for biodiesel.