Evaluation of grape stalks as a bioresource

The compositional characteristics of grape stalk in terms of lignin, sugars, ash, extractives and tannins contents were established. The biomass composition of grape stalk is 34% lignin, 36% cellulose, 24% hemicellulose and 6% tannins. The tannins, analysed by solution ¹³C NMR, were essentially of procyanidin type and the dichloromethane extractives fraction, characterized by GC-MS, was mainly composed of fatty acids. Different processes for the pretreatment of grape stalk were compared. Due to the high content of lignin and tannins, dilute sulfuric acid and ethanol organosolv pretreatments resulted in a low degree of delignification. However, a wet oxidation process permitted a significant reduction of the Klason lignin content of the pulp with a good carbohydrate recovery and improved enzymatic digestibility.     

Fractionation of flax shives with pressurized aqueous ethanol

Fractionation of flax shives into major biopolymer constituents, such as cellulose, hemicelluloses, and lignin, was carried out with pressurized aqueous ethanol in a pressurized low-polarity water extractor. The effect of processing parameters such as temperature, ethanol concentration, flow rate, sample size and solvent/feed ratio on the simultaneous extraction of hemicelluloses and lignin was determined. More than 80% of total hemicelluloses and ∼78% of total lignin were removed simultaneously in a single step under the following conditions: 180 °C, 30% (v/v) ethanol concentration, 3 mL/min flow rate, and 45 mL/g solvent/feed ratio. Under these extraction conditions, cellulose degradation was negligible. Further, the separation of lignin from hemicelluloses was carried out using two simple alternative methodologies based on precipitation. Since no acidic or alkali catalysts were used, the degradation of biopolymers was negligible and the oligomer/monomer ratio of sugars was 825:1. Characterization of fractionated biopolymers was carried out with scanning electron microscopy and a Fourier-transform infrared spectrometer (FT-IR). FT-IR spectra of isolated lignin and hemicelluloses showed that both polymers were comparable to commercially available products.     

Structural characterization and isolation of lignin and hemicelluloses from barley straw

Structural characterization and isolation of lignin and hemicelluloses from crops are very important for industrial utilization. In this paper, the sequential treatments of barley straw using 90% dioxane, 80% acidic dioxane, 100% dimethyl sulfoxide, and 8% NaOH released total 93% of original lignin and 87% of original hemicelluloses. The extractions with acidic dioxane and dimethyl sulfoxide produced the original hemicelluloses and high-condensed lignin mainly from the middle lamella. FT-IR and NMR analyses show that the hemicelluloses of barley straw contain acidic arabinxylans as the major polysaccharides, which are substituted by α-l-arabinofuranose, 4-O-methyl-glucuronic acid, acetyl group (DS = 0.13), and xylose at O-3 and/or O-2 of xylan, and lignin contains β-O-4′ as a predominant interunit linkage with high amounts of β-5′ and β-1′. The guaiacyl and syringyl units are more etherified, and the proportion of erythro-β-O-4′ is slightly higher than that of threo-β-O-4′ in the lignin of barley straw.     

Processing of Lespedeza stalks by pretreatment with low severity steam and post-treatment with alkaline peroxide

The steam pre-treatment with low severity preserves valuable biomass components, and further delignification with alkaline peroxide could improve hydrolysis. A combination of low severity steam pretreatment and alkaline peroxide post-treatment of Lespedeza stalks was investigated. The post-treatment of steam-pretreated Lespedeza stalks with alkaline peroxide significantly increased the cellulose content and changed the structure of the cellulose-rich fractions. A glucose yield of 503.5 mg g⁻¹ raw material from enzyme hydrolysis was obtained when the steam-pretreated material (184 °C for 4 min) was post-treated with 2% hydrogen peroxide at 60 °C for 24 h with a substrate concentration of 3.3%. Its hydrolysis yield is 88.8%, which is higher than that of samples processed by steam pretreatment alone (63.7%). The samples obtained by post-treatment with alkaline peroxide were found to have a smoother surface and looser structure in scanning electron microscopy images. The isolated lignin preparations had a yield range from 10.9 to 14.7 (% dry matter). The lignin was characterized by thermogravimetric analysis/differential thermal analysis, Fourier transform infrared spectroscopy, and gel permeation chromatography. Alkaline peroxide treatment increased the thermal stability of lignin, and decreased the amounts of all functional groups. Depolymerization and repolymerization occurred during the alkaline peroxide treatment.     

Fractional isolation and partial characterization of non-starch polysaccharides and lignin from sago pith

Sago pith non-starch polysaccharides were fractionated into cold water solubles (2.6%), hot water solubles (0.8%), dimethylsulfoxide solubles (0.8%), 5% NaOH soluble hemicelluloses (1.2%), 24% KOH–2% H₃BO₃ soluble hemicelluloses (0.6%), and cellulose (5.3%). Lignin was measured by 5% NaOH extraction (0.6%) and sodium chlorite oxidation (4.2%). Glucose and rhamnose were the major sugars in cold and hot water soluble non-starch polysaccharides. The neutral sugars in dimethylsulfoxide (DMSO) soluble non-starch polysaccharides were found to be enriched in rhamnose, xylose, glucose, and arabinose. Extraction of sago pith with aqueous 5% NaOH produced hemicelluloses, which were enriched in xylose and, to a lesser extent, glucose, arabinose, galactose, and rhamnose-containing polysaccharides, together with 7.4% uronic acids and 3.9% lignin. Further extraction of the delignified pith residue with aqueous 24% KOH and 2% H₃BO₃ removed the residual hemicellulosic fraction, which was enriched in glucose and xylose-containing polysaccharides, together with 5.8% uronic acids and 1.1% associated residual lignin. Six phenolic acids and aldehydes were detected in the mixtures of alkaline nitrobenzene oxidation of 5% NaOH soluble lignin and associated lignin in hemicelluloses and cellulose fractions. The lignin fraction contained a high proportion of non-condensed syringyl units and small amounts of non-condensed guaiacyl units as well as fewer non-condensed p-hydroxyphenyl units.     

Gorse (Ulex europæus) as a possible source of xylans by hydrothermal treatment

Autocatalytic hydrothermal process conditions were used to study Ulex europæus (Gorse) as a source of xylan compounds. The aim was to study the possibilities for using this unutilised biomass material to produce xylans. Ulex is an evergreen shrub that grows in the northwest of Spain and has no economic value. Therefore, Ulex is considered a promising candidate as a biomass source. Ulex showed a total xylose content of 12%, thus qualifying it as a suitable material to extract xylan-derived compounds. Autohydrolysis was applied to extract xylans from Ulex. To find the best conditions for xylan extraction, samples of Ulex were subjected to different temperatures and time conditions. Results indicate that autohydrolysis is a suitable method to selectively extract xylans at temperatures between 160 and 190 °C for 5-30 min, reaching a maximum xylan recovery of almost 63% of the initial xylan at 180 °C for 30 min, with only small effects on cellulose and lignin contents.     

Thermochemical characterisation of straws and high yielding perennial grasses

The research is concerned with thermochemical characterisation of straws and high yielding perennial grasses. Crops selected for this study include wheat straw (Triticum aestivum), rape straw (Brassica napus), reed canary grass (Phalaris arundinacea) and switch grass (Panicum virgatum). Thermogravimetric analysis (TGA) was used to examine the distribution of char and volatiles during pyrolysis up to 900 °C. Utilising multi-heating rate thermogravimetric data, the Friedman iso-conversional kinetic method was used to determine pyrolysis kinetic parameters. Light and medium volatile decomposition products were investigated using pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) up to 520 °C. The 22 highest yielding identifiable cellulose, hemicellulose and lignin biomass markers were semi-quantified taking into consideration peak areas from GC chromatograms. Notable differences can be seen in butanedioic acid, dimethyl ester (hemicelluloses decomposition products), 2-methoxy-4-vinylphenol (lignin marker) and levoglucosan (intermediate pyrolytic decomposition product of cellulose) content when comparing perennial grasses with straw. From results presented in this study, perennial grasses such as switch grass, have the most attractive properties for fast pyrolysis processing. This is because of the observed high volatile yield content of 82.23%, heating value of 19.64 MJ/kg and the relatively low inorganic content.     

Chemical characterization of various parts of nipa palm (Nypa fruticans)

The current study was initiated to characterize various parts of nipa palm (Nypa fruticans) to establish whole utilization of this biomass as potential raw material for fuels and chemicals. Nipa consisting of frond, shell, husk and leaf was chemically characterized for cellulose, hemicellulose, lignin, starch, protein, extractives and inorganic constituents for its each part. The total chemical composition showed that the cellulose and hemicellulose contents were in the range of 28.9-45.6 wt% and 21.8-26.4 wt%, respectively. The hemicellulose was rich with glucuronoxylan. The lignin content was 19.4-33.8 wt% with the highest lignin content found in leaf. The alkaline nitrobenzene oxidation products showed that nipa palm lignin mainly consists of guaiacyl and syringyl propane units with a small amount of p-hydroxyphenylpropane unit. Besides the main chemical components, starch, protein and extractives were also present in significant amounts from 2 to 8 wt%. Additionally, the ash content was high from 5.1 to 11.7 wt%, consisting of the major inorganic elements being Na, K and Cl with minor inorganic elements of Mg, Ca, Si, P, S and Al. Overall, each part of the nipa palm has its individual superior characteristics and could be exploited as lignocellulosic resources for fuels and chemicals.     

Extraction of condensed tannins from grape pomace for use as wood adhesives

The extraction of condensed tannins from grape pomace was examined using a mixture water-sodium hydroxide at 120 °C. The extracts were characterized by solution ¹³C NMR and have showed characteristic consistent with that of condensed tannins with dominant procyanidin units. The tannin fractions reactivity toward formaldehyde was studied by gel time analysis and thermomechanical analysis in bending. It has been demonstrated that the extracts obtained by using 10% of NaOH (w/w) displayed promising properties for adhesive applications.     

Pretreatment of partially delignified hybrid poplar for biofuels production: Characterization of organosolv hemicelluloses

In this study, extraction of hemicelluloses from the carbohydrate-enriched residues was successfully carried out with organic solvent and the residue was used for bio-based energy production. The chemical composition and physico-chemical properties of six hemicelluloses released were elucidated by a combination of sugar analysis, molecular determination, Fourier transform infrared, and ¹H, ¹³C and 2D-HSQC NMR spectroscopy. The results showed that the successful treatments resulted in a fractionation of the native hemicelluloses. The sugar analysis indicated that xylose (47.14-56.91%) was found to be the major sugar components and small amounts of glucose (14.1-19.06%) and mannose (12.41-18.09%) were also observed in these hemicellulosic fractions. Further studies by NMR spectroscopy exhibited that the acetylated hemicellulosic fraction had a main structure of (1 → 4)-linked β-d-xylopyranosyl backbone with 4-O-methyl-α-d-glucuronic acid as a side chain and a minor structure of linear β-(1 → 4)-linked glucomannans. Furthermore, these hemicelluloses possessed a low substituted degree which was beneficial for enzymatic saccharification.     

Ethanol production from alkali- and ozone-treated cotton stalks using thermotolerant Pichia kudriavzevii HOP-1

In the present study, milled cotton stalks were subjected to alkali pretreatment with NaOH at 1-4% (w/v) concentrations at 121 °C for time ranging from 30 to 90 min. Ozone pretreatment was performed by passing 45 mg/L of ozone gas over 2 mm cotton stalks for 150 min at a flow rate of 0.37 L/min. The residual biomass from 4% alkali pretreatment for 60 min showed 46.6% lignin degradation accompanied by 83.2% increase in glucan content, compared with the untreated biomass. Hydrolysis of 4% alkali-treated and ozone-treated cotton stalks was conducted using enzyme combination of 20 filter paper cellulase units/gram dried substrate (FPU/g-ds), 45 IU/g-ds β-glucosidase and 15 IU/g-ds pectinase. Enzymatic hydrolysis of alkali-treated and ozone-treated biomass after 48 h resulted in 42.29 g/L glucose, 6.82 g/L xylose and 24.13 g/L glucose, 8.3 g/L xylose, respectively. About 99% of glucose was consumed in 24 h by Pichia kudriavzevii HOP-1 cells resulting in 19.82 g/L of ethanol from alkali-treated cotton stalks and 10.96 g/L of ethanol from ozone-treated cotton stalks. Simultaneous saccharification and fermentation of the alkali-treated cotton stalks after 12-h pre-hydrolysis resulted in ethanol concentration, ethanol yield on dry biomass basis and ethanol productivity of 19.48 g/L, 0.21 g/g and 0.41 g/L/h, respectively which holds promise for further scale-up studies. To the best of our knowledge, this is the first study employing SSF for ethanol production from cotton stalks.     

Sequential extractions and structural characterization of lignin with ethanol and alkali from bamboo (Neosinocalamus affinis)

A sequential process with the combination of ethanol and alkali aqueous solutions was utilized to extract lignin from bamboo (Neosinocalamus affinis), a potential lignocellulosic material. In this case, the successive treatments of dewaxed bamboo with 70% ethanol at 80 °C, 0.2 and 0.5 M NaOH, 70% ethanol containing 0.6 M NaOH, and 1.0, 2.0, and 3.0 M NaOH at 50 °C, resulted in a total yield of acid-insoluble lignin fractions of 10.06%, corresponding to release of 62.25% original lignin from the cell walls. The lignin fractions obtained were then characterized by GPC, FT-IR, NMR spectroscopy, and sugar analysis. As compared to the alkali lignin fractions, the ethanol-soluble lignin fraction had a relatively higher molecular weight (2670 g/mol) and the content of carbohydrates primarily consisted of glucose 2.01% and xylose 1.90%. This suggested that the carbohydrate chains linked to lignin may increase the hydrodynamic volume of lignin and therefore increase the apparent molecular weight of the ethanol-soluble lignin. HSQC spectra analysis revealed that the alkali lignin fractions consisted mainly of β-O-4′ linkages combined with small amounts of β-β′, β-5′, β-1′ linkages, and p-hydroxycinnamyl alcohol end groups. Furthermore, minor amounts of esterified p-coumaric and ferulic acids were also detected in the lignins isolated.     

Thermal transitions of the amorphous polymers in wheat straw

The thermal transitions of the amorphous polymers in wheat straw were investigated using dynamic mechanical thermal analysis (DMTA). The study included both natural and solvent extracted wheat straw, in moist (8-9% water content) and dry conditions, and was compared to spruce samples. Under these conditions two transitions arising from the glass transition of lignin and hemicelluloses have been identified. Key transitions attributed to softening of lignin were found at 53, 63 and 91 °C for moist samples of wheat straw, extracted straw and spruce, respectively. Transitions for hemicelluloses were determined at 2, −1 and 5 °C, respectively. Differences are likely due to different compositions of lignin and hemicelluloses from straw and spruce and structural differences between the raw materials. The high wax content in wheat straw resulted in a transition at about 40 °C which was absent in solvent extracted wheat straw samples and spruce. This specific transition was further investigated and confirmed by differential scanning calorimetry (DSC) of extracted wheat straw wax. Information about the thermal transitions is of great importance for the utilization of wheat straw in pelletizing, briquetting and fiber board manufacturing.     

Cynara cardunculus L. — a new fibre crop for pulp and paper production

The pulping potential of the thistle Cynara cardunculus L. was evaluated by studying anatomy and chemical composition of the stalks and Kraft pulp yields and properties. C. cardunculus is a perennial plant, with annual harvests, that can be grown in hot and dry climates with high productivities. The stalk of the plant has a central pith, ca. 45% in volume and 10% in weight, of small parenchyma cells, surrounded by a cortex where numerous fibre vascular bundles are imbedded. The fibres are on average 1.3 mm long, 18.8 μm wide and have a 4.8 μm wall thickness. The whole stalks have 7.7% ash, 14.6% extractives, 17.0% lignin and 53.0% polysaccharides, mainly cellulose and xylans. The pith has more lignin than the depithed stalk (20.3 vs. 13.6%). The Cynara stalks could be cooked by standard Kraft pulping to produce well delignified pulps with high yields (44–47% with Kappa 11–15), low rejects and very good strength properties, especially in relation to tensile strength. Depithing of the stalks has a positive impact on pulp yield, chemical consumption and on the pulp strength properties.     

Comparative study of organosolv lignins from wheat straw

Dewaxed wheat straw was treated with acetic acid–H₂O (65/35, v/v), acetic acid–H₂O (80/20, v/v), acetic acid–H₂O (90/10, v/v), formic acid–acetic acid–H₂O (20/60/20, v/v/v), formic acid–acetic acid–H₂O (30/60/10, v/v/v), methanol–H₂O (60/40, v/v) and ethanol–H₂O (60/40, v/v) using 0.1% HCl as a catalyst at 85 °C for 4 h, in which 78.2, 80.0, 88.2, 89.4, 94.1, 23.5 and 37.4% of the original lignin, and 42.4, 58.7, 70.0, 65.1, 76.5, 14.2 and 22.2% of the original hemicelluloses was released, respectively. Lignins obtained were characterized by their content of hemicelluloses, composition of phenolic acids and aldehydes, molecular weight, thermal stability and by UV, Fourier transform infrared (FT-IR), ¹H and ¹³C nuclear magnetic resonance (NMR) spectroscopy. The results showed that aqueous organic acid was more effective than aqueous organic alcohol for extensive delignification and selective fractionation of cellulose, lignin and hemicelluloses from the straw. In particular, the addition of formic acid gave a significant effect on the dissolution of lignin. All the acid-insoluble lignin fractions contained small amounts of contaminated hemicelluloses as shown by their content of neutral sugars, 0.9–4.3%, and had weight-average molecular weight between 3960 and 4340 g mol⁻¹. An increase in concentration of acetic acid or formic acid in organosolv resulted in an increment in release of guaiacyl units and in lignin condensation. However, the lignin preparations released during the treatment with aqueous organic alcohol without organic acid contained almost equal amounts of non-condensed guaiacyl and syringyl units with fewer p-hydroxyphenyl units. The β-O-4 ether bonds together with β-β, β-5 and 5-5′ carbon–carbon linkages were identified to be present in lignin substructures.     

Ester and ether linkages between hydroxycinnamic acids and lignins from wheat,rice, rye,and barley straws,maize stems,and fast-growing poplar wood

Treatment of solvent extracted wheat, rice, rye, and barley straws, maize stems, and fast-growing poplar wood with 60% aqueous ethanol in 0.2 M HCl at 75 °C for 3 h released 51.8, 51.2, 47.2, 43.7, 54.0, and 16.7% of the original lignin, and 44.3, 50.3, 30.9, 36.1, 40.0, and 25.5% of the original hemicelluloses, respectively. It was found that the bulk of p-coumaric acid (PCA) (67.0–83.5%) was esterified at the lignin side chains, while ferulic acid (FA) is linked to lignin side chains through both ether bonds (51.6–68.3%) and ester bonds (31.7–48.4%), indicating that FA may form intra- and/or inter-molecular ester–ether bridges between lignin fragments, which is first proposed in this study. In addition to p-hydroxybenzoic acid esterified to lignins in the cell walls of wheat straw and fast-growing poplar wood, a small portion of ether-linked p-hydroxybenzoic acid in the lignin preparations, obtained from rice, rye, and barley straws and maize stems, was also detected. It was also detected that noticeable amounts of syringic and vanillic acids were predominantly esterified to the lignin molecules in the cell walls of the materials studied.     

Mild peroxyformic acid fractionation of Miscanthus × giganteus bark. Behaviour and structural characterization of lignin

Miscanthus × giganteus bark was subjected to mild fractionation with peroxyformic acid by a two stage process. A factorial experimental design was used to study and quantify the effect of the variables (formic acid concentration (80-90%), hydrogen peroxide concentration (0.2-0.4%), temperature of the first stage (60-80 °C), and treatment time of the second stage (60-120 min)) on the main parameters of fractionation: pulp yield, remaining lignin and total polysaccharides in pulp. The dependence of lignin precipitation rate on hydrogen peroxide concentration in liquor was also studied. Hydrogen peroxide concentrations inferior to 0.5% seems to be suitable to recover high percentages of lignin. The isolated lignin was analysed by 2D-HSQC, ¹³C- and ³¹P NMR spectroscopy, FTIR spectroscopy, size-exclusion chromatography and chemical analysis. The most important chemical modifications taken place in the lignin during the fractionation were identified: β-O-4′ cleavage and hydrolysis of LC-bond structures. The C9-formula was also determined: C₉H_6.81O_2.90(OCH₃)_0.68(COOH)_0.07(OH^Ph)_0.38(OH^Al)_0.33.     

钾硅肥配施对胡麻茎秆碳水化合物及抗倒性的影响

为明确钾硅肥施用对胡麻茎秆碳水化合物主要成分含量及抗倒伏特性的影响,探讨钾硅肥运筹调控胡麻茎秆抗倒伏能力的机制,选用裂区试验设计进行了研究,以两个品种为主处理,三个K2O钾肥用量(K0:不施钾;K1:52.5 kg/hm2;K2:105 kg/hm2)为副处理,两个SiO2硅肥用量(Si0:不施硅;Si1:90 kg/...     

Relationship of physicochemical characteristics and hydrolyzed hydroxycinnamic acid profile of barley varieties and nutrient availability in ruminants

The objectives of this study were to (1) investigate the relationship between physicochemical characteristics (mean/median particle sizes, physical hull content) and hydrolyzed hydroxycinnamic acid profile (ferulic acid (FA), para-coumaric acid (pCA), and their ratio) of barley varieties and in situ rumen degradability in dairy cattle; and (2) investigate rumen degradation kinetics of FA and pCA of CDC barley varieties grown in western Canada. Barley variety had a significant effect (P < 0.05) on rumen undegradable fraction of DM, FA, pCA, neutral (NDF) and acid detergent fiber (ADF) at 12 and/or 24 h of rumen incubation. FA in barley grain was more degradable than the pCA (P < 0.05). There were no differences (P > 0.05) in effective degradability of DM (EDDM) and EDFA, but significant differences in EDpCA (P < 0.05). Barley hull was strongly correlated to NDF, ADF, ADL, hemicellulose and cellulose (R > 0.78, P < 0.001) and correlated to FA (R = 0.57, P < 0.05) but not to pCA (R = 0.42, P > 0.05) in original samples. FA and pCA were highly and positively correlated to NDF, ADF, ADL, hemicellulose, cellulose, mean/median particle sizes, and rumen indigestible DM, NDF and ADF at either 12 or 24 h (P < 0.05). Mean/median particle size of barley grain positively influenced the rumen indigestible DM, but not others (FA, pCA). The results implied that reduction of barley hull, FA and pCA contents could increase the degradability of barley grain in rumen. Multi-regression with best model variable selection analysis revealed that FA was the factor most inhibiting to DM degradability of barley in rumen, and was the most effective factor to predict DM degradability, while hull was the most effective factor to determine NDF degradability in rumen. Both hull and FA affected ADF degradability in the rumen. The results indicate that breeding or identifying barley varieties with lower hull and FA contents would result in higher degradability, higher energy density and higher quality barley and improve nutrient availability of barley.     

Isolation of cellulose with ionic liquid from steam exploded rice straw

Isolation of cellulose from straw is a bottleneck for exploiting such biomass resources. In recent years, considerable concerns have arisen over new efficient and environmentally friendly way for this purpose. A novel method for cellulose isolation has been proposed by dissolving steam exploded rice straw in 1-allyl-3-methylimidazolium chloride ionic liquid (IL), following regeneration of crude cellulose by diluting the cellulose-ionic liquid solution adequately after separation of insoluble residues. The crude cellulose was then bleached by 2% hydrogen peroxide aqueous solution with low-flux ozone blowing into. No acid-insoluble lignin and only 0.85% hemicelluloses were detected in the bleached cellulose. The isolated cellulose was analyzed by SEM, FT-IR, ¹³C CP/MAS solid state NMR, XRD spectroscopes, and the results indicated that high quality cellulose preparation could be isolated in this manner from rice straw.