Showing papers on "Hemicellulose published in 2008"
TL;DR: Effective parameters in pretreatment of lignocelluloses, such as crystallinity, accessible surface area, and protection by lignin and hemicellulose are described first, and several pretreatment methods are discussed and their effects on improvement in ethanol and/or biogas production are described.
Abstract: Lignocelluloses are often a major or sometimes the sole components of different waste streams from various industries, forestry, agriculture and municipalities. Hydrolysis of these materials is the first step for either digestion to biogas (methane) or fermentation to ethanol. However, enzymatic hydrolysis of lignocelluloses with no pretreatment is usually not so effective because of high stability of the materials to enzymatic or bacterial attacks. The present work is dedicated to reviewing the methods that have been studied for pretreatment of lignocellulosic wastes for conversion to ethanol or biogas. Effective parameters in pretreatment of lignocelluloses, such as crystallinity, accessible surface area, and protection by lignin and hemicellulose are described first. Then, several pretreatment methods are discussed and their effects on improvement in ethanol and/or biogas production are described. They include milling, irradiation, microwave, steam explosion, ammonia fiber explosion (AFEX), supercritical CO2 and its explosion, alkaline hydrolysis, liquid hot-water pretreatment, organosolv processes, wet oxidation, ozonolysis, dilute- and concentrated-acid hydrolyses, and biological pretreatments.
2,510 citations
Journal Article•
TL;DR: In this paper, the authors provide a review of the use of pre-treatment for hemicellulose in a lignocellulose feedstock-based biorefinery.
Abstract: Biomass pretreatment (BP) plays a crucial role in a lignocellulose feedstock-based biorefinery (LCFBR) for processing of three major output streams (cellulose, hemicelluloses and lignin) into chemicals and biofuels. BP includes processing of lignocellulosic material (LCM) under aqueous, dilute acid or alkaline media to obtain a cellulosic fraction, which is then fermented to produce bioethanol. Hemicellulose is usually treated as a secondary stream due to lack of efficient fermentation of hemicellulosic sugars to ethanol. This review provides BPs assuming that hemicellulose stream should be integrated in LCFBR as a primary fraction for converting into value-added compounds other than bioethanol. Different LCM treatments are analyzed foreseeing bio-based products possible to obtain from hemicellulose path.
667 citations
TL;DR: The structure of mannans and some biochemical properties and applications of mannan-degrading enzymes are reported, showing a complex system of sulfated structure.
Abstract: Hemicellulose is a complex group of heterogeneous polymers and represents one of the major sources of renewable organic matter. Mannan is one of the major constituent groups of hemicellulose in the wall of higher plants. It comprises linear or branched polymers derived from sugars such as d-mannose, d-galactose, and d-glucose. The principal component of softwood hemicellulose is glucomannan. Structural studies revealed that the galactosyl side chain hydrogen interacts to the mannan backbone intramolecularly and provides structural stability. Differences in the distribution of d-galactosyl units along the mannan structure are found in galactomannans from different sources. Acetyl groups were identified and distributed irregularly in glucomannan. Some of the mannosyl units of galactoglucomannan are partially substituted by O-acetyl groups. Some unusual structures are found in the mannan family from seaweed, showing a complex system of sulfated structure. Endohydrolases and exohydrolases are involved in the breakdown of the mannan backbone to oligosaccharides or fermentable sugars. The main-chain mannan-degrading enzymes include β-mannanase, β-glucosidase, and β-mannosidase. Additional enzymes such as acetyl mannan esterase and α-galactosidase are required to remove side-chain substituents that are attached at various points on mannan, creating more sites for subsequent enzymatic hydrolysis. Mannan-degrading enzymes have found applications in the pharmaceutical, food, feed, and pulp and paper industries. This review reports the structure of mannans and some biochemical properties and applications of mannan-degrading enzymes.
590 citations
TL;DR: In this article, the authors summarized the decomposition mechanisms and hydrolysis products of cellulose, hemicellulose, and lignocellulosic biomass materials under various conditions in hot-compressed water.
Abstract: Biomass hydrolysis extracts, particularly sugars and other useful derivatives, are important products for further conversion to produce biofuels. The past 2 decades have witnessed significant research and development activities using hot-compressed water for the hydrolysis and conversion of cellulose, hemicellulose, and lignocellulosic biomass materials. This paper summarizes the decomposition mechanisms and hydrolysis products of these materials under various conditions in hot-compressed water. Key factors determining hydrolysis behavior in hot-compressed water are also discussed. Comparisons are made between hydrolysis in hot-compressed water and hydrolysis using other technologies, including acid hydrolysis, alkaline hydrolysis, and enzymatic hydrolysis. Advantages, disadvantages, typical operation conditions, products properties, and applicability are summarized. Key research issues on hydrolysis in hot-compressed water are identified, and future research prospects to further improve the technology ar...
449 citations
TL;DR: In this paper, the authors explored the mechanisms of biogas yield enhancement through solid-state sodium hydroxide (NaOH) pretreatment of rice straw during anaerobic digestion and found that the changes of chemical structures and physical characteristics of lignin, hemicellulose, and cellulose made rice straw become more available and biodegradable.
Abstract: The biogas yield of rice straw during anaerobic digestion can be substantially increased through solid-state sodium hydroxide (NaOH) pretreatment. This study was conducted to explore the mechanisms of biogas yield enhancement. The chemical compositions of the pretreated rice straw were first analyzed. Fourier transform infrared (FTIR), hydrogen-1 nuclear magnetic resonance spectroscopy ( 1 H NMR), X-ray diffraction (XRD), and gas permeation chromatography (GPC) were then used to investigate the changes of chemical structures and physical characteristics of lignin, hemicellulose, and cellulose. The results showed that the biogas yield of 6% NaOH-treated rice straw was increased by 27.3-64.5%. The enhancement of the biogas yield was attributed to the improvement of biodegradability of the rice straw through NaOH pretreatment. Degradation of 16.4% cellulose, 36.8% hemicellulose, and 28.4% lignin was observed, while water-soluble substances were increased by 122.5%. The ester bond of lignin-carbohydrate complexes (LCCs) was destroyed through the hydrolysis reaction, releasing more cellulose for biogas production. The linkages of interunits and the functional groups of lignin, cellulose, and hemicellulose were either broken down or destroyed, leading to significant changes of chemical structures. The original lignin with a large molecular weight and three-dimensional network structure became one with a small molecular weight and linear structure after NaOH pretreatment. The cellulosic crystal style was not obviously changed, but the crystallinity of cellulose increased. The changes of chemical compositions, chemical structures, and physical characteristics made rice straw become more available and biodegradable and thus were responsible for the enhancement of the biogas yield.
405 citations
TL;DR: Delignification by the sodium chlorite method improved the initial rate of hydrolysis by cellulolytic enzymes significantly, resulting in a higher yield of monosaccharides as compared with that for untreated samples.
Abstract: The effects of cellulose crystallinity, hemicellulose, and lignin on the enzymatic hydrolysis of Miscanthus sinensis to monosaccharides were investigated. A air-dried biomass was ground by ball-milling, and the powder was separated into four fractions by passage through a series of sieves with mesh sizes 250–355 μm, 150–250 μm, 63–150 μm, and <63 μm. Each fraction was hydrolyzed with commercially available cellulase and β-glucosidase. The yield of monosaccharides increased as the crystallinity of the substrate decreased. The addition of xylanase increased the yield of both pentoses and glucose. Delignification by the sodium chlorite method improved the initial rate of hydrolysis by cellulolytic enzymes significantly, resulting in a higher yield of monosaccharides as compared with that for untreated samples. When delignified M. sinensis was hydrolyzed with cellulase, β-glucosidase, and xylanase, hemicellulose was hydrolyzed completely into monosaccharides, and the conversion rate of glucan to glucose was 9...
359 citations
TL;DR: Rice hulls, a complex lignocellulosic material with high lignin and ash content, has the potential to serve as a low‐cost feedstock for production of ethanol and was evaluated for conversion of rice hull cellulose and hemicellulose to monomeric sugars.
Abstract: Rice hulls, a complex lignocellulosic material with high lignin (15.38 +/- 0.2%) and ash (18.71 +/- 0.01%) content, contain 35.62 +/- 0.12% cellulose and 11.96 +/- 0.73% hemicellulose and has the potential to serve as a low-cost feedstock for production of ethanol. Dilute H2SO4 pretreatments at varied temperature (120-190 degrees C) and enzymatic saccharification (45 degrees C, pH 5.0) were evaluated for conversion of rice hull cellulose and hemicellulose to monomeric sugars. The maximum yield of monomeric sugars from rice hulls (15%, w/v) by dilute H2SO4 (1.0%, v/v) pretreatment and enzymatic saccharification (45 degrees C, pH 5.0, 72 h) using cellulase, beta-glucosidase, xylanase, esterase, and Tween 20 was 287 +/- 3 mg/g (60% yield based on total carbohydrate content). Under this condition, no furfural and hydroxymethyl furfural were produced. The yield of ethanol per L by the mixed sugar utilizing recombinant Escherichia colistrain FBR 5 from rice hull hydrolyzate containing 43.6 +/- 3.0 g fermentable sugars (glucose, 18.2 +/- 1.4 g; xylose, 21.4 +/- 1.1 g; arabinose, 2.4 +/- 0.3 g; galactose, 1.6 +/- 0.2 g) was 18.7 +/- 0.6 g (0.43 +/- 0.02 g/g sugars obtained; 0.13 +/- 0.01 g/g rice hulls) at pH 6.5 and 35 degrees C. Detoxification of the acid- and enzyme-treated rice hull hydrolyzate by overliming (pH 10.5, 90 degrees C, 30 min) reduced the time required for maximum ethanol production (17 +/- 0.2 g from 42.0 +/- 0.7 g sugars per L) by the E. coli strain from 64 to 39 h in the case of separate hydrolysis and fermentation and increased the maximum ethanol yield (per L) from 7.1 +/- 2.3 g in 140 h to 9.1 +/- 0.7 g in 112 h in the case of simultaneous saccharification and fermentation.
332 citations
TL;DR: In this paper, the effect of hemicellulose and lignin on cellulose conversion into glucose was investigated using a commercial cellulase concentrate (Celluclast 1.5L) in an enzyme/substrate ratio of 45 FPU/g, 2% (w/v) substrate concentration, 45°C for 96h.
315 citations
TL;DR: In this article, pyrolysis of sawdust and its three components (cellulose, hemicellulose and lignin) were performed in a thermogravimetric analyzer under syngas and hydrogen.
261 citations
TL;DR: In this article, the authors investigated the influence of potassium on the pyrolysis behavior of cellulose and lignin, and showed that the effect of the addition of 1% of potassium in the form of potassium acetate has a huge influence on the char formation stage and increases the char yields.
240 citations
TL;DR: The LA yield as a function of the process conditions was modelled using a kinetic model originally developed for the acid-catalysed hydrolysis of cellulose and good agreement between the experimental and modelled data was obtained.
TL;DR: In this article, the acid hydrolysis was carried out in an acid recycle process and detoxification of hydrolysate was performed by electrodialysis, two cycles of acidic treatments increased the reducing sugar concentration from 28 to 63.
TL;DR: In this paper, a review provides an overview of variables to be considered in the utilization of fungal plant-depolymerizing enzymes produced by solid-state fermentation from agricultural production residues in Brazil.
TL;DR: In this article, the transverse size of cellulosic microfibers from bagasse was analyzed using scanning electron microscopy (SEM) and atomic force microscopy (AFM).
TL;DR: The HCW treatment is useful in improving the milling efficiency and can save energy and enzyme loading, and the BM treatment simultaneously improved the digestibility of both glucan and xylan.
Abstract: Background
Lignocellulosic biomass such as wood is an attractive material for fuel ethanol production. Pretreatment technologies that increase the digestibility of cellulose and hemicellulose in the lignocellulosic biomass have a major influence on the cost of the subsequent enzymatic hydrolysis and ethanol fermentation processes. Pretreatments without chemicals such as acids, bases or organic solvents are less effective for an enzymatic hydrolysis process than those with chemicals, but they have a less negative effect on the environment.
TL;DR: In this article, the maximum yield of monomeric sugars from rice hulls (15.6±0.0%, w/v) by lime pretreatment (100mg−g−1 hulls, 121°C, 1h) and enzymatic saccharification (45 °C, pH 5.0, 72 ¼h) using a cocktail of three commercial enzyme preparations (cellulase, β-glucosidase and hemicellulase) at the dose level of 0.15ml of each enzyme preparation was 154±
Abstract: Rice hulls used in this study contained 35.6±0.1% cellulose and 12.0±0.7% hemicellulose. The maximum yield of monomeric sugars from rice hulls (15.0%, w/v) by lime pretreatment (100 mg g−1 hulls, 121 °C, 1 h) and enzymatic saccharification (45 °C, pH 5.0, 72 h) using a cocktail of three commercial enzyme preparations (cellulase, β-glucosidase and hemicellulase) at the dose level of 0.15 ml of each enzyme preparation g−1 hulls was 154±1 mg g−1 (32% yield). The lime pretreatment did not generate any detectable furfural and hydroxymethyl furfural in the hydrolyzate. The concentration of ethanol from lime-pretreated enzyme-saccharified rice hull (138 g) hydrolyzate by recombinant Escherichia coli strain FBR5 at pH 6.5 and 35 °C in 19 h was 9.8±0.5 g l−1 with a yield of 0.49 g g−1 available sugars. The ethanol concentration was 11.0±1.0 g l−1 in the case of simultaneous saccharification and fermentation by the E. coli strain at pH 6.0 and 35 °C in 53 h.
TL;DR: The citrus-processing industry generates in the Mediterranean area huge amounts of orange peel as a byproduct from the industrial extraction of citrus juices to reduce its environmental impact as well as to provide an extra profit, this residue was investigated in this study as an alternative substrate for the fermentative production of citric acid.
Abstract: The citrus-processing industry generates in the Mediterranean area huge amounts of orange peel as a byproduct from the industrial extraction of citrus juices. To reduce its environmental impact as well as to provide an extra profit, this residue was investigated in this study as an alternative substrate for the fermentative production of citric acid. Orange peel contained 16.9% soluble sugars, 9.21% cellulose, 10.5% hemicellulose, and 42.5% pectin as the most important components. To get solutions rich in soluble and starchy sugars to be used as a carbon source for citric acid fermentation, this raw material was submitted to autohydrolysis, a process that does not make use of any acidic catalyst. Liquors obtained by this process under optimum conditions (temperature of 130 °C and a liquid/solid ratio of 8.0 g/g) contained 38.2 g/L free sugars (8.3 g/L sucrose, 13.7 g/L glucose, and 16.2 g/L fructose) and significant amounts of metals, particularly Mg, Ca, Zn, and K. Without additional nutrients, these liq...
TL;DR: There was a near linear dependence on acid concentration observed for xylose degradation and the results suggest that mixtures of biomass species may be processed together and still achieve high yields for all species.
TL;DR: A pilot plant (IBUS) consisting of three reactors was used for hydrothermal treatment of wheat straw aiming at co-production of bioethanol (from sugars) and electricity (from lignin) and the highest water addition gave the highest hemicellulose recovery.
TL;DR: W Whole-genome transcriptome analysis revealed that there is significant upregulation of the glycolytic pathway and an ABC-type sugar transporter during growth on glucose and xylose, indicating that C. saccharolyticus coferments these sugars unimpeded by glucose-based catabolite repression.
Abstract: Caldicellulosiruptor saccharolyticus is an extremely thermophilic, gram-positive anaerobe which ferments cellulose-, hemicellulose- and pectin-containing biomass to acetate, CO2, and hydrogen. Its broad substrate range, high hydrogen-producing capacity, and ability to coutilize glucose and xylose make this bacterium an attractive candidate for microbial bioenergy production. Here, the complete genome sequence of C. saccharolyticus, consisting of a 2,970,275-bp circular chromosome encoding 2,679 predicted proteins, is described. Analysis of the genome revealed that C. saccharolyticus has an extensive polysaccharide-hydrolyzing capacity for cellulose, hemicellulose, pectin, and starch, coupled to a large number of ABC transporters for monomeric and oligomeric sugar uptake. The components of the Embden-Meyerhof and nonoxidative pentose phosphate pathways are all present; however, there is no evidence that an Entner-Doudoroff pathway is present. Catabolic pathways for a range of sugars, including rhamnose, fucose, arabinose, glucuronate, fructose, and galactose, were identified. These pathways lead to the production of NADH and reduced ferredoxin. NADH and reduced ferredoxin are subsequently used by two distinct hydrogenases to generate hydrogen. Whole-genome transcriptome analysis revealed that there is significant upregulation of the glycolytic pathway and an ABC-type sugar transporter during growth on glucose and xylose, indicating that C. saccharolyticus coferments these sugars unimpeded by glucose-based catabolite repression. The capacity to simultaneously process and utilize a range of carbohydrates associated with biomass feedstocks is a highly desirable feature of this lignocellulose-utilizing, biofuel-producing bacterium.
TL;DR: In this article, a comprehensive study of the acid hydrolysis of the softwood species, Loblolly pine (Pinus taeda), using different acid conditions is presented.
Abstract: A comprehensive study of the acid hydrolysis of the softwood species, Loblolly pine (Pinus taeda), using different hydrolysis conditions is presented. The effect of the type of acid, pH, reaction temperature, and reaction time on hydrolysis products such as monosaccharides (mannose, glucose, galactose, xylose, and arabinose) and the subsequent degradation products, 5-hydroxymethyl-2-furaldehyde (HMF) and 2-furaldehyde (furfural) is reported using a batch reactor. Trifluoroacetic acid (TFA) is found to yield the highest amount of overall soluble monosaccharides (∼70% yield from the hemicelluloses fraction) at 150 °C at pH 1.65. The mineral acids (HCl, H2SO4, HNO3, and H3PO4) gave a slightly lower yield of monosaccharides from hydrolyzed hemicellulose (∼60%). At 200 °C, cellulose is hydrolyzed by the mineral acids as evidenced by higher levels of solid dissolution and higher soluble hexose (relative to pentose) yields. Larger amounts of degradation products are also noted at higher temperatures. Furthermore...
TL;DR: In this paper, the authors showed that glucose is the main component of the enzymatic hydrolysates, which made GC seem to be more effective than the DNS method for analysis of the enzymes as it can detect the concentration of monosaccharide more accurately.
Abstract: To minimize the cost of cellulase production, both pretreatment of the rice straw and on-site enzyme production were realized. Rice straw was first pretreated by 2% NaOH, which could increase cellulose by 54.83%, and decreased hemicellulose by 61.07% and lignin by 36.24%, respectively. Detected by SEM, significant morphological changes were observed in the tissue. Through orthogonal experiments, temperature 35 °C, initial pH value 4.5 and the rotation speed of shaking bed 180 rpm were determined to be the optimal conditions for hydrolysis of rice straw by Trichoderma reesei ZM4-F3. After hydrolysis for 96 h, the production of FPA and reducing sugars could achieve 2.231 g l−1 and 12.92 U ml−1, respectively. Moreover, T. reesei ZM4-F3 can decompose 68.21% of pretreated rice straw after 120 h of hydrolysis. By GC analysis, it showed that glucose is the main component of the enzymatic hydrolysates, which made GC seem to be more effective than the DNS method for analysis of the enzymatic hydrolysates as it can detect the concentration of each kind of monosaccharide more accurately.
TL;DR: A fungal isolate, Coniochaeta ligniaria NRRL30616, metabolizes furfural and 5hydroxymethylfurfural (HMF) as well as aromatic and aliphatic acids and aldehydes as mentioned in this paper.
TL;DR: In this article, the hydrothermal dissolution profile of the wood components cellulose, hemicelluloses, and lignin of a hardwood mixture during autohydrolysis in a modified Dionex ASE-100 is described.
Abstract: Hemicelluloses derived from biomass are presently underutilized. In order to develop more profitable biorefinery processes, the mechanism responsible for hemicellulose removal by pretreatments has to be further explored. The hydrothermal dissolution profile of the wood components cellulose, hemicelluloses, and lignin of a hardwood mixture during autohydrolysis in a modified Dionex ASE-100 is described. Well-closed material balances were obtained for lignin-free yield, xylan, and glucomannan when comparing the solid and liquid phases. Xylo-oligomers were the predominant component in the extract. Xylan initially dissolved as oligosaccharides and then slowly depolymerized into monomeric xylose. The residual xylan in wood was only slightly deacetylated. A smaller amount of glucomannan was removed as oligosaccharides. Arabinose and galactose were completely removed from wood as monomers at the end of the extraction process. Initially all acetyl groups were removed while still bound to oligosaccharides. Then, a...
TL;DR: The 96-well Biomass Conversion Research Lab (BCRL) microplate method is a high-throughput assay to study digestibility of lignocellulosic biomass as a function of biomass composition, pre-treatment severity, and enzyme composition.
Abstract: Several factors will influence the viability of a biochemical platform for manufacturing lignocellulosic based fuels and chemicals, for example, genetically engineering energy crops, reducing pre-treatment severity, and minimizing enzyme loading. Past research on biomass conversion has focused largely on acid based pre-treatment technologies that fractionate lignin and hemicellulose from cellulose. However, for alkaline based (e.g., AFEX) and other lower severity pre-treatments it becomes critical to co-hydrolyze cellulose and hemicellulose using an optimized enzyme cocktail. Lignocellulosics are appropriate substrates to assess hydrolytic activity of enzyme mixtures compared to conventional unrealistic substrates (e.g., filter paper, chromogenic, and fluorigenic compounds) for studying synergistic hydrolysis. However, there are few, if any, high-throughput lignocellulosic digestibility analytical platforms for optimizing biomass conversion. The 96-well Biomass Conversion Research Lab (BCRL) microplate method is a high-throughput assay to study digestibility of lignocellulosic biomass as a function of biomass composition, pre-treatment severity, and enzyme composition. The most suitable method for delivering milled biomass to the microplate was through multi-pipetting slurry suspensions. A rapid bio-enzymatic, spectrophotometric assay was used to determine fermentable sugars. The entire procedure was automated using a robotic pipetting workstation. Several parameters that affect hydrolysis in the microplate were studied and optimized (i.e., particle size reduction, slurry solids concentration, glucan loading, mass transfer issues, and time period for hydrolysis). The microplate method was optimized for crystalline cellulose (Avicel) and ammonia fiber expansion (AFEX) pre-treated corn stover.
TL;DR: A combined sulfuric acid‐free ethanol cooking and pulverization process was developed to achieve the complete saccharification of the cellulosic component of woody biomass, thereby avoiding the problems associated with the use of strong acid catalysts.
Abstract: A combined sulfuric acid-free ethanol cooking and pulverization process was developed in order to achieve the complete saccharification of the cellulosic component of woody biomass, thereby avoiding the problems associated with the use of strong acid catalysts. Eucalyptus wood chips were used as a raw material and exposed to an ethanol/water/acetic acid mixed solvent in an autoclave. This process can cause the fibrillation of wood chips. During the process, the production of furfural due to an excessive degradation of polysaccharide components was extremely low and delignification was insignificant. Therefore, the cooking process is regarded not as a delignification but as an activation of the original wood. Subsequently, the activated solid products were pulverized by ball-milling in order to improve their enzymatic digestibility. Enzymatic hydrolysis experiments demonstrated that the conversion of the cellulosic components into glucose attained 100% under optimal conditions. Wide-angle X-ray diffractometry and particle size distribution analysis revealed that the scale affecting the improvement of enzymatic digestibility ranged from 10 nm to 1 microm. Field emission scanning electron microscopy depicted that the sulfuric acid-free ethanol cooking induced a pore formation by the removal of part of the lignin and hemicellulose fractions in the size range from a few of tens nanometers to several hundred nanometers.
TL;DR: A sulfuric acid-free ethanol cooking (SFEC) treatment was developed to achieve complete saccharification of the cellulosic component of eucalyptus and baggase flour, thereby avoiding the problems associated with the use of strong acid catalysts.
TL;DR: It was found that the three-pseudocomponent model with n- order kinetics was more accurate than the model with first-order kinetics at most cases to describe the pyrolysis of the hemicellulose.
TL;DR: Experimental results indicated that bi‐phasic behavior dominated at low temperatures, which may be due to the insufficient removal of acetyl groups, and a combination of experimental data and model analysis suggests that around 80–90% xylose yields can be achieved at reaction temperatures between 100 and 150°C with 0.2 M maleic acid.
Abstract: Maleic acid-catalyzed hemicellulose hydrolysis reaction in corn stover was analyzed by kinetic modeling. Kinetic constants for Saeman and biphasic hydrolysis models were analyzed by an Arrhenius-type expansion which include activation energy and catalyst concentration factors. The activation energy for hemicellulose hydrolysis by maleic acid was determined to be 83.3 +/- 10.3 kJ/mol, which is significantly lower than the reported E(a) values for sulfuric acid catalyzed hemicellulose hydrolysis reaction. Model analysis suggest that increasing maleic acid concentrations from 0.05 to 0.2 M facilitate improvement in xylose yields from 40% to 85%, while the extent of improvement flattens to near-quantitative by increasing catalyst loading from 0.2 to 1 M. The model was confirmed for the hydrolysis of corn stover at 1 M maleic acid concentrations at 150 degrees C, resulting in a xylose yield of 96% of theoretical. The refined Saeman model was used to evaluate the optimal condition for monomeric xylose yield in the maleic acid-catalyzed reaction: low temperature reaction conditions were suggested, however, experimental results indicated that bi-phasic behavior dominated at low temperatures, which may be due to the insufficient removal of acetyl groups. A combination of experimental data and model analysis suggests that around 80-90% xylose yields can be achieved at reaction temperatures between 100 and 150 degrees C with 0.2 M maleic acid.
TL;DR: The water-soluble fractions from both the classical and ultrasonics experiments were shown to exhibit significant radical scavenging activity in vitro, indicating their potential application as polysaccharide-based antioxidants.