Valorization of residual woody biomass (Olea europaea trimmings) based on aqueous fractionation

BACKGROUND: Olive tree trimmings, a widely available agricultural residue lacking added value applications, were subjected to treatments with hot, compressed water under a variety of operational conditions. As a result of treatments, hemicelluloses were solubilized, and the treated solids were enriched in cellulose and lignin. Spent solids from autohydrolysis were assayed as substrates for enzymatic hydrolysis and for bioethanol production by simultaneous saccharification and fermentation. RESULTS: Liquors from the aqueous fractionation stage resulted in the formation of soluble hemicellulose‐derived saccharides (mainly of oligomeric nature) at yields up to 26.2 g per 100 g oven‐dry raw material. Enzymatic hydrolysis of spent solids from the aqueous fractionation step led to solutions containing up to 58.8 g glucose L^?1 (corresponding to cellulose to glucose conversions up to 83.2%). Simultaneous saccharification and fermentation assays using spent solids as substrates enabled the production of media containing up to 38.2 g ethanol L^?1, corresponding to 72% of the stoichiometric amount. CONCLUSION: Aqueous (or hydrothermal) processing is a technology enabling the recovery of hemicelluloses (as soluble saccharides) and the production of spent solids with high susceptibility to enzymatic hydrolysis (suitable for bioethanol production by simultaneous saccharification and fermentation). Copyright © 2011 Society of Chemical Industry     

Structural changes of cellulose,wood, and paper under shear deformation and high pressure

Structural changes of wood and its components have been studied after shear deformation under high pressure (SDHP) at up to 6 GPa. Cellulose amorphization and chain depolymerization was observed. Approximately 30% of microcrystalline cellulose was soluble in water after a 360-degree twist of the Bridgman anvils. The water-insoluble part was re-crystallized into cellulose II lattice. Repeated treatment applied to the nondissolved part of the sample, the so-called cascade experiment, permits the dissolving of about 30% of the residual nondissolved material once again. Extraction with water, followed by 10% sodium hydroxide, allows almost complete dissolving of microcrystalline cellulose (98%). Water-soluble saccharides were studied by HPLC and ¹³C NMR. It was found that destruction of the wood lignin network needs more severe treatment conditions than cellulose destruction does. Lignin domains in wood act as “grinding stones” during cellulose destruction. Long-living lignin free radicals have been detected with EPR after SDHP. ¹³C NMR CP/MAS spin diffusion studies showed that SDHP leads to separation of wood components into different biopolymer domains, which turns the system toward thermo-dynamic equilibrium. SDHP does not permit achievement of initial compulsary compatibility of components in native wood. SDHP technique appears as a promising method for wood delignification and carbohydrate saccharification in the solid state without using harmful chemical reagents of solvents, which is important for technological safety and ecology. © 1994 John Wiley & Sons, Inc.     

One-Step Fractionation of the Main Components of Bamboo by Formic Acid-based Organosolv Process Under Pressure

To promote the efficient utilization of lignocellulosic materials, one-step fractionation by formic acid-based organosolv process under pressure has been studied for converting lignocellulose in its main components. Lignin and hemicelluloses were selectively dissolved, while cellulose was not obviously degraded. Under optimized conditions (85% formic acid, a liquor-to-solid ratio of 7:1, and a temperature of 145°C for 45 min), this process provided a high efficient way to separate the main components of bamboo, obtaining 42.2% cellulose pulp, 31.5% lignin, 8.5% hemicellulose-rich fraction, 3.56% furfural and 3.80% acetic acid. Cellulose pulp with satisfying viscosity could easily be bleached to a high brightness of over 87% ISO with a short bleaching sequence, and had an acceptable paper strength properties. The recovered lignin fraction contained a small amount of carbohydrates and a considerable part of proteins and p-hydroxycinnamates. Additionally, the organic substances in hemicellulose-rich fraction obtained was composed of 95% carbohydrates, most of which was monosaccharides, as well as 5% lignin.     

Multi-Stage Hydrothermal Processing of Eucalyptus Globulus Wood: An Experimental Assessment

Eucalyptus globulus wood samples were subjected to hydrothermal processing according to a three-stage, crossflow scheme with intercalated washing stages. The operational conditions for each hydrothermal stage were selected based on previous experiments, as the kinetics and yields depended on the composition of the reaction media. The solid recovery yields as well as the compositions of the various solids and liquids involved in each stage were measured, in order to allow the formulation of material balances. Under the conditions selected, the various stages enabled solid recovery yields in the range 70.8–74.4?g/100?g oven-dry wood, with extensive hemicellulose removal and almost quantitative recovery of both cellulose and lignin in solid phase. The production of valuable polysaccharide-derived products (including saccharides and furans) along the process decreased owing to the different initial composition of the various reaction media. In turn, the generation of monosaccharides from soluble saccharides of oligomeric or polymeric nature was promoted in the second and third stages. The experimental data provided in this study allow a quantitative assessment on the considered process, a basic information for simulation and economic evaluation.     

Characteristics of cellulose isolated by a totally chlorine‐free method from Caragana korshinskii

The chemical composition and fiber morphology of Caragana korshinskii were investigated in this study. Isolation of cellulose was performed in a nonsulfur acetic acid/nitric acid system under various conditions. The influence of three factors, i.e., nitric acid concentration (0, 2, 4, 6, 8, or 10%), temperature (95, 100, 110, 115, 120, or 130°C), and reaction time (30, 40, 50, 60, or 90 min) on the cellulose properties (viscosity, yield, and molecular weight) was studied. The cellulose isolated was characterized by using Fourier transform infrared, gas chromatography, high performance liquid chromatography, solid‐state cross‐polarization magic angle spinning carbon‐13 nuclear magnetic resonance, wide‐angle X‐ray diffraction, and thermogravimetric analysis/differential scanning calorimetry techniques. The results showed that the treatment using 80% acetic acid and nitric acid as a catalyst under the given conditions resulted in slight acetylation of the cellulose and increased the degree of crystallinity of cellulose except for significant degradation of lignin and hemicellulosic polymers. The thermal stability of the cellulose declined with an increase in nitric acid concentration. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3251–3263, 2006     

Optimization of beech wood pulping in catalyzed acetic acid media

Fagus sylvatica wood samples were treated in HCl‐catalyzed, acetic acid solutions. The effects of selected operational variables (catalyst concentration, reaction time and liquor to wood ratio) on pulp yield, composition of pulps and composition of pulping liquors were assessed using incomplete, second‐order, centred, factorial designs. Pulp composition was measured by the contents in cellulose, xylan and lignin. The concentrations of glucose, xylose and furfural in pulping liquors were also considered as experimental variables. Under selected conditions, pulps with 5.8% to 7.5% Klason lignin (kappa numbers in the range 25 to 33), 77.2% to 85.3% cellulose and 3.3% to 6.1% xylan were obtained at 45.8% to 50.0% pulp yield. The selected pulps showed good SCAN viscosity (723 to 814 mL/g) and alkaline resistances which were affected by the acetyl group content of samples (6.6 to 7.6 weight percent).     

Preparation of microcrystalline cellulose from rice straw under microwave irradiation

Crude cellulose was isolated from rice straw and then converted into microcrystalline cellulose (MCC) via partial hydrolysis. Both the isolation and partial hydrolysis were carried out under microwave. Rice straw was successively pretreated with alkaline and acid solutions before hydrolysis. Lignin and silica were almost removed but partial removal of hemicellulose in dilute alkali solution, and the residual hemicellulose was further removed in dilute acid solution. The total removal rates of hemicellulose, lignin and silica reached up 92.0%, 98.5%, and 96.8%, respectively. The cellulose content of 93.6 wt % in MCC was given by partial hydrolysis of crude cellulose isolated from rice straw. The comparison between microwave irradiation and traditional heating method was also investigated. Compared to traditional heating method, similar results were obtained while milder conditions, including shorter time and lower temperature, were required. An effective microwave‐assisted and energy‐efficient methodology using rice straw as the alternative source of cellulose fiber was developed. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44901.     

Molecular weights and molecular weight distributions of irradiated cellulose fibers by gel permeation chromatography

Radiation degradation of cellulose fibers was investigated by gel permeation chromatography (GPC). Scoured cotton of Mexican variety (cellulose I), Polynosic rayon (cellulose II), and their microcrystalline celluloses obtained by hydrolysis of the original fibers were irradiated by Co-60 γ-rays under vacuum or humid conditions. The irradiated samples were then nitrated under nondegradative conditions. The molecular weights and molecular weight distributions were measured by GPC using tetrahydrofran as solvent. The relationship between molecular weight and elution count was obtained with cellulose trinitrate standards fractionated by preparative GPC. The degree of polymerization of the fibers decreased with increasing irradiation dose, but their microcystalline celluloses were only slightly degraded by irradiation, especially in microcrystalline cellulose from cellulose I. Degradation of the fibers irradiated under humid conditions was less than that irradiated under vacuum. It was found that the G-values for main-chain scission for the irradiated cellulose I, cellulose II, microcrystalline cellulose I, and microcrystalline cellulose II were 2.8, 2.9, less than 1, and 2.9, respectively, but the G-value for main-chain scission for the irradiated cellulose II was increased to 11.2 at irradiation doses above 3 Mrad. Consequently, it is inferred that cellulose molecules in the amorphous regions are degraded more readily, and the well-aligned molecules in crystalline regions are not as easily degraded by irradiation.     

秸秆中木质素对其超低酸水解过程的影响

以湖北稻草秸秆为研究对象,研究了超低酸水解木质纤维素的适宜条件,测定了适宜条件下的超低酸法水解15种不同种类秸秆的纤维素及半纤维素的转化率、还原糖得率及结晶度的变化。实验结果表明:秸秆投料量3 g、硫酸投料量45 mL(硫酸质量分数0.05%)、搅拌转速500 r/min、反应温度210 ℃、反应时间10 min为适宜的水解条件。对15种不同种类秸秆的水解结果统计得到,随着秸秆中木质素含量的增大,纤维素和半纤维素的转化率都逐渐降低,还原糖得率逐渐降低;通过SEM和X衍射分析水解前后的木质纤维素结构,得到了木质素影响水解过程的方式:1)木质素含量越大,纤维素的结晶度越大,纤维素的非晶化越困难,从而影响了纤维素的水解;2)原木质素不溶于反应体系且在酸性条件下相对稳定,富木质素层的木质素阻碍反应物与产物扩散,使富木质素层内的纤维素、半纤维素水解速率降低;3)木质素含量越高,木质纤维素的富木质素层越厚、强度越大,水解时难以从颗粒表面脱落,进一步降低水解速率。     

H3PW12O40·4H2O as an efficient catalyst for the conversion of cellulose into partially substituted cellulose acetate

The preparation of partial acetylation of cellulose derived from rice straw was catalyzed by phosphotungstic acid with various numbers of crystal water, and H₃PW₁₂O₄₀·4H₂O was found to be as effective catalyst. The yield of the cellulose acetate was significantly enhanced by converting cellulose directly isolated from rice straw into microcrystalline cellulose before acetylation. The optimization of the acetylation was investigated by varying the amount of catalyst and acetic anhydride as well as reaction conditions including reaction time and medium, and a degree of substitution (DS) value of 2.29 and yield of 62.9% were obtained under the optimized conditions. The structure and the formation of the acetylated product were confirmed by Fourier transform infrared spectroscopy (FTIR) and powder X‐ray diffraction (XRD) technique, the thermal properties were determined by thermal analysis including thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC), and the morphology was observed by scanning electron microscope (SEM). © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41212.     

基于PY-GC/MS的生物质组分间相互作用的热解实验

为研究生物质三组分间热裂解过程中的相互作用,利用热裂解-气相色谱/质谱联用仪（PY-GC/MS）联用的方法,对纤维素、木聚糖（半纤维素的模化物）和木质素进行单独热裂解及两两组分混合热裂解实验。单组分实验结果表明,在热解温度600℃、热解时间10s条件下纤维素的热解产物主要以左旋葡聚糖为主,木聚糖以乙酸和糠醛为主,而木质素主要以酚类物质为主。组分混合热裂解实验结果表明,纤维素促进了木聚糖热裂解生成更多的乙酸和糠醛,而木聚糖和木质素对纤维素热解生成左旋葡聚糖具有强烈的抑制作用;纤维素和木聚糖的存在大大促进了木质素热裂解生成酚类物质,而木质素抑制了木聚糖热裂解生成乙酸和糠醛。此外,研究还发现混合组分热解的相互作用受到热解温度和停留时间的影响。     

Enhanced ethanol production from enzymatically treated steam‐exploded rice straw using extractive fermentation

Alcohol fermentation of an enzymatic hydrolyzate of exploded rice straw was studied experimentally. Rice straw was treated under variable conditions, such as steam pressure and steaming time. The exploded rice straw was separated into water‐soluble material, methanol‐soluble lignin, Klason lignin, and a mixture of cellulose and a low molecular weight substance. The effects of steam explosion on the characteristics of the exploded rice straw were clarified from the point of view of the amounts of extractive components. Steam explosion was found to be effective for the delignification of rice straw and for increasing its susceptibility to enzyme hydrolysis and alcohol fermentation. The polysaccharides (cellulose and hemicellulose) in the rice straw treated at a steam pressure of 3.5 MPa with a steaming time of 2 min were hydrolyzed almost completely into monosaccharides, (ie glucose and xylose) by a mixture of Trichoderma viride cellulase (Meicelase) and Aspergillus aculeatus cellulase (Acucelase). The enzymatic hydrolyzate of exploded rice straw was converted into ethanol efficiently by Pichia stipitis and the ethanol yield from sugar was about 86%(w/w) of the theoretical value. The ethanol concentration in a membrane bioreactor coupled with a pervaporation system reached 50 gdm^?3 and was about five times higher than that in the culture broth. The energy efficiency (ratio of combustion energy of ethanol produced to energy for steam explosion) reached a maximum value at a pressure of 3.5 MPa for 2 min. © 2001 Society of Chemical Industry     

Sustainable Production of Levulinic Acid from the Cellulosic Fraction of Pinus Pinaster Wood: Operation in Aqueous Media Under Microwave Irradiation

The fractionation of the structural components of lignocellulosic biomass (cellulose, hemicelluloses, and lignin) and the separate utilization of the resulting fractions for specific purposes, according to the philosophy of biorefineries, enables the development of sustainable processes for biomass utilization. In this work, Pinus pinaster wood was subjected to aqueous processing to remove water-soluble extractives and hemicelluloses, and the resulting solid was subjected to pulping with HCl-catalyzed acetic acid solutions (Acetosolv method). The pulp was employed as a substrate for levulinic acid manufacture by reaction in acidic media under microwave irradiation. The effects of the major operational variables (temperature, reaction time, and acid concentration) on the levulinic acid yield were established by statistical modeling of experimental data. Operating under the best reaction conditions (at 191.2°C for 18.9 min in aqueous media containing 1.10% HCl), the levulinic acid yield accounted for 56.4% of the stoichiometric value.     

微晶纤维素醋酸酯的合成与工艺研究

以微晶纤维素为原料,浓硫酸为催化剂,制备了一系列不同取代度的纤维素醋酸酯。研究了反应时间、温度、原料配比、催化剂用量对取代度和产率的影响,并通过红外图谱进行了表征。结果表明：随着反应时间、反应温度、原料配比和催化剂用量的增加,产物取代度增大,但产率降低。在温度为85℃,时间为10min,浓硫酸用量为1mL,醋酸酐与微晶纤维素的用量比为25∶1的最佳合成条件下取代度接近3,与理论值相符合。     

稻草秸秆综纤维素对阿司匹林片崩解性能的影响

以稻草秸秆为原料,经过SO₃微热爆预处理、木质素降解、漂白等工序制备出了稻草秸秆综纤维素,并将其用作片剂崩解剂进行了性能评价。参照《中国药典》(2015版)中的有关规定,检测了稻草秸秆综纤维素的各项指标;以阿司匹林为模型药物,以市售微晶纤维素为对照,测定了稻草秸秆综纤维素的崩解性能。结果表明,稻草秸秆综纤维素质量符合《中国药典》(2015版)中的相关规定,且崩解性明显优于市售微晶纤维素,可用作片剂崩解剂。在稻草秸秆综纤维素用量为3％~5%时即可达到微晶纤维素用量为15%~20%的崩解效果,这一效果的呈现与稻草秸秆综纤维素的形态结构以及含有半纤维素组分有着密切联系。     

Totally chlorine‐free bleaching of Acetosolv pulps: a clean approach to dissolving pulp manufacture

Eucalyptus globulus wood samples were delignified in media containing concentrated acetic acid, water and hydrochloric acid (Acetosolv process) under optimized conditions, and the pulps were subjected to totally chlorine‐free (TCF) bleaching. Alkaline extractions, oxygen delignification, ozone treatment, enzymatic xylan removal and hydrogen peroxide oxidation in alkaline media were investigated as individual steps in selected bleaching sequences. Under the best conditions, fully bleached pulps with favourable characteristics for dissolving pulp manufacture were obtained. © 2001 Society of Chemical Industry     

甲酸―盐酸体系下木质纤维素的组分分离

研究了常压下甲酸―盐酸体系中木屑的溶解规律,结合酸回收和碱沉方法实现了木屑的组分分离。经酸体系处理后的剩余物主要成分为纤维素,滤液经酸回收和碱沉后得到的沉淀是木质素,半纤维素全部水解。实验确定了最佳分离条件:在甲酸―盐酸(体积比3∶1)体系中,溶解温度为60℃,溶解时间为180min,液固比为10∶1,在此条件下,木屑的溶解率可达48.8%,木质素收率为23.2%。通过FTIR、XRD及NMR等方法对溶解后及甲酸回收后剩余物质的结构进行了分析确证。     

Simulated autohydrolysis of aspen milled wood lignin in the presence of aromatic additives. Changes in molecular weight distribution

The reactions between aspen milled wood lignin (MWL) and 2-naphthol, resorcinol, and p-hydroxybenzoic acid were studied under simulated autohydrolysis conditions. The material after the reaction was separated into a dioxane-insoluble fraction (DI), a dioxane-soluble but ether-insoluble fraction (DSEI), and an ether-soluble fraction (ES). In the absence of additive, the lignin first depolymerized and remained solvent soluble, then repolymerized to become insoluble. With 2-naphthol as additive, the amount of DI lignin decreased proportionally to the amount of additive present. When more than 0.1 mole of 2-naphthol/C-9 unit was present, no DI lignin was formed, that is, all the lignin was soluble. Gel permeation chromatography studies indicated that the additive was acting effectively as a blocking agent, preventing lignin repolymerization. Small amounts of resorcinol acted as a repolymerizing agent since two or more fragments of lignin could readily condense with a molecule of the very active additive. As a result of this bridging effect, the amount of DI lignin increased. As the amount of resorcinol was increased, it behaved more like a blocking agent and a reduction in the amount of DI lignin was observed. The presence of a large excess of resorcinol resulted in the formation of soluble lignin only. The molecular weight distributions supported the proposed dual role of resorcinol as a bridging or blocking agent. The use of an excess of p-hydroxybenzoic acid prevented the formation of DI material and resulted in low molecular weight soluble lignin.     

Valorisation of waste fractions from autohydrolysis of selected lignocellulosic materials

Non‐isothermal processing of lignocellulosic materials in aqueous media (autohydrolysis reaction) under mild conditions leads to solutions containing valuable chemicals (oligosaccharides, sugars and acetic acid) and other, undesired, compounds (belonging to the extractive and acid‐soluble lignin fractions) which have to be removed in further purification treatments. Liquors obtained by non‐isothermal autohydrolysis of Eucalyptus globulus wood and corncobs under a variety of operational conditions were extracted with ethyl acetate in order to remove non‐saccharide components, and the suitability of the fraction dissolved in the organic phase was assayed for possible utilisation as an antioxidant. The yield and antioxidant activity of ethyl acetate extracts (measured by the α,α‐diphenyl‐β‐picrylhydrazyl (DPPH) radical scavenging capacity) showed a strong dependence on the autohydrolysis conditions. The antioxidant activity of extracts obtained under selected operational conditions compared well with synthetic antioxidants. © 2003 Society of Chemical Industry     

Properties of native and immobilised preparations of β-D-glucosidase from Aspergillus niger

The enzyme β-D-glucosidase from Aspergillus niger has been immobilised through its carbohydrate moiety on concanavalin A-Sepharose and on cyanogen bromide-activated Sepharose after aminoalkylation of the carbohydrate side chains of the enzyme. For comparison, the enzyme was also immobilised on microcrystalline cellulose through its protein moiety. High retention of activity and a decrease in K_m and V_max. were observed when β-D-glucosidase was immobilised by these methods. An increase in the thermal stability of the immobilised β-D-glucosidase preparations over the soluble enzyme was achieved if it was treated with glutaraldehyde before its adsorption on concanavalin A-Sepharose or if the enzyme immobilised on cyanogen bromide-activated Sepharose was subsequently treated with glutaraldehyde. Treatment of β-D-glucosidase immobilised on microcrystalline cellulose with glutaraldehyde hardly increased its thermal stability over the soluble enzyme.