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Oil palm empty fruit bunch (EFB) as the main lignocellulosic residue from the oil palm industry serves as suitable feedstock for enzymatic saccharification, yielding fermentable sugars. Due to complex inter-association between hemicellulose, cellulose and lignin within EFB lignocellulosic matrix, different saturated steam conditions at 140-230 °C, 0.3-2.3 MPa was chosen as a pretreatment strategy, targeted to hydrolyze hemicellulose and reduce crystallinity of cellulose to enhance enzymatic saccharification which need no chemical requirement and potential for energy recovery. As a result, SEM analysis of EFB morphology indicated that the enhanced silica body removal from 190-230 °C of saturated steam pretreatment correspondingly led to substantial 82% removal of hemicellulose. Consequently, enzymatic saccharification yielded between 0.621-0.637 g glucose per g EFB, equivalent to 93-95% of cellulose saccharification by Acremonium cellulase on EFB treated with saturated steam at 210-230 °C. Notably, a short duration pretreatment of EFB at 210 °C for 2 min was proved sufficient for high fermentable sugar production. The potential energy estimated for employing saturated steam pretreatment of EFB in a palm oil mill was sufficient by 2.2 x 1012 kJ/year. [ABSTRACT FROM AUTHOR]

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Corn cob is an abundant agricultural residue worldwide, with high potential and interesting composition, and its valorization still needs to be studied. Selectively fractionating its structural components (hemicellulose, cellulose, and lignin), value-added products can be produced, eliminating waste. In this work, integrated fractionation approaches were developed and evaluated. First, an organosolv process was optimized (ethanol:water, 50:50, w/w). Then, as a comparative method, alkaline delignification (using NaOH, 1–2%) was also studied. The organosolv process allowed a significant delignification of the material (79% delignification yield) and, at the same time, a liquid phase containing a relevant concentration (14.6 g/L) of xylooligosaccharides (XOS). The resulting solid fraction, rich in cellulose, showed an enzymatic digestibility of 90%. The alkaline process increased the delignification yield to 94%, producing a solid fraction with a cellulose enzymatic digestibility of 83%. The two later techniques were also used in a combined strategy of hydrothermal processing (autohydrolysis) followed by delignification. The first allowed the selective hydrolysis of hemicellulose to produce XOS-rich hydrolysates (26.8 g/L, 67.3 g/100 g initial xylan). The further delignification processes, alkaline or organosolv, led to global delignification yields of 76% and 93%, respectively. The solid residue, enriched in glucan (above 75% for both combined processes), also presented high enzymatic saccharification yields, 89% and 90%, respectively. The fractionation strategies proposed, and the results obtained are very promising, enabling the integrated upgrading of this material into a biorefinery framework. [ABSTRACT FROM AUTHOR]

Among the oil palm biomass, oil palm frond leaves (OPFLs) are under-valued since they can be classified as a high recalcitrance feedstock due to the high lignin and hemicellulose content. This work proposes a new way of using OPFLs as alternative cellulose sources for glucose conversion by an application of various pre-treatments at varying parameters. From green pre-treatment, steam explosion (SE) is much more effective in disrupting the OPFLs structure in contrast to hydrothermal (HT) pre-treatment, by a vast dissolution of hemicellulose and depolymerization of lignin. The pre-impregnation with H 2 SO 4 prior to steam explosion was beneficial to enhance the hemicellulose removal up to 89.94 %. The 2D-HSQC NMR analysis divulged the reduction of ß-O-4 linkage and S/G value after the SE and HT pre-treatment, verifying the degradation of lignin-carbohydrate linkage in OPFLs. Meanwhile, the dilute NaOH pre-treatment enhanced the delignification by 87.14 %. SEM analysis revealed a well-disrupted structure of pre-treated OPFLs exposing a higher cellulosic fraction, whereas SEC analysis divulged a decreasing pattern of degree of polymerization of cellulose. The enzymatic analysis revealed that pre-treated OPFLs yielded higher glucose ranging from 29.81 % to 49.98 % w/w, which was ∼3-fold higher than raw OPFLs (14.31 % w/w). A maximum cellulose digestibility (100 %) was achieved by steam-exploded OPFLs after 72 h of enzymatic hydrolysis. This suggests the potency of various pre-treatments to enhance enzymatic saccharification of OPFLs producing a higher glucose yield. [Display omitted] • The oil palm fronds leaves (OPFLs) was pre-treated via various pre-treatments. • The cellulose content of dilute NaOH pre-treated OPFLs was increased up to 49 % w/w. • The steam exploded OPFLs pulp exhibited a well-disrupted cell wall structure. • The amount of ß-O-4 linkages in extracted lignin of pre-treated OPFLs was reduced. • The pre-treated OPFLs yielded 49 % w/w of glucose and 100 % cellulose digestibility. [ABSTRACT FROM AUTHOR]

Three different types of biomass sourced from forestry waste (eucalyptus residues), agricultural waste (wheat straw), and energy crop (miscanthus) were used as starting materials to produce hemicellulosic sugars, furans (furfural and hydroxymethylfurfural), and oligosaccharides. A two-step hybrid process was implemented; biomass was first autohydrolysed without any additive to extract hemicelluloses and dissolve it in water. Then, the hydrolysate was treated with a solid acid catalyst, TiO2-WOx, in order to achieve hydrolysis and produce monomeric sugars and furans. This article investigates the role of the biomass type, autohydrolysis experimental conditions, polymerisation degree and composition of hemicelluloses on the performance of the process coupling autohydrolysis and catalytic hydrolysis. The highest global yields of both oligosaccharides and monomeric sugars were obtained from Eucalyptus (37% and 18%, respectively).

Hemicelluloses are amorphous polymers of sugar molecules that make up a major fraction of lignocellulosic biomasses. They have applications in the bioenergy, textile, mining, cosmetic, and pharmaceutical industries. Industrial use of hemicellulose often requires that the polymer be hydrolyzed into constituent oligomers and monomers. Traditional models of hemicellulose degradation are kinetic, and usually only appropriate for limited operating regimes and specific species. The study of hemicellulose hydrolysis has yielded substantial data in the literature, enabling a diverse data set to be collected for general and widely applicable machine learning models. In this paper, a dataset containing 1955 experimental data points on batch hemicellulose hydrolysis of hardwood was collected from 71 published papers dated from 1985 to 2019. Three machine learning models (ridge regression, support vector regression and artificial neural networks) are assessed on their ability to predict xylose yield and compared to a kinetic model. Although the performance of ridge regression was unsatisfactory, both support vector regression and artificial neural networks outperformed the simple kinetic model. The artificial neural network outperformed support vector regression, reducing the mean absolute error in predicting soluble xylose yield of test data to 6.18%. The results suggest that machine learning models trained on historical data may be used to supplement experimental data, reducing the number of experiments needed.

We propose a closed-loop pretreatment process, wherein volatiles produced during steam explosion pretreatment were recovered and reintroduced as acid catalysts into the pretreatment system. The volatiles were separated through a drastic decompression process followed by a steam explosion process and recovered as a liquified catalyst (LFC) through a heat exchanger. The LFC effectively served as an acid catalyst for hemicellulose hydrolysis, significantly decreasing residence time from 90 min to 30 min to achieve 80 % conversion yield at 170 °C. Hydrolysates with high content of lower molecular weight oligomeric sugars were obtained using LFC, and were considered advantageous for application as prebiotics. These results are attributed to the complementary features of acetic acid and furfural contained within the LFC. Computational simulation using Aspen Plus was used to investigate the effects of recycling on LFC, and it demonstrated the feasibility of the catalyst-recirculating system. A validation study was conducted based on simulation results to predict the actual performance of the proposed pretreatment system. Based on these results, the recirculating system was predicted to improve the conversion yield and low-molecular weight oligomers yield by 1.5-fold and 1.6-fold, respectively. [Display omitted] [ABSTRACT FROM AUTHOR]

Three different types of biomass sourced from forestry waste (eucalyptus residues), agricultural waste (wheat straw), and energy crop (miscanthus) were used as starting materials to produce hemicellulosic sugars, furans (furfural and hydroxymethylfurfural), and oligosaccharides. A two-step hybrid process was implemented; biomass was first autohydrolysed without any additive to extract hemicelluloses and dissolve it in water. Then, the hydrolysate was treated with a solid acid catalyst, TiO2-WOx, in order to achieve hydrolysis and produce monomeric sugars and furans. This article investigates the role of the biomass type, autohydrolysis experimental conditions, polymerisation degree and composition of hemicelluloses on the performance of the process coupling autohydrolysis and catalytic hydrolysis. The highest global yields of both oligosaccharides and monomeric sugars were obtained from Eucalyptus (37% and 18%, respectively). [ABSTRACT FROM AUTHOR]

Background: Autohydrolysis is an extensively investigated pretreatment method due to its environmental friendliness. During autohydrolysis, most xylan from hemicellulose can be converted into xylooligosaccharides (XOS), and cellulose in the autohydrolyzed residues can be transformed into glucose after enzymatic hydrolysis. Both of these are value-added biochemicals in the biorefining process. In this work, paper mulberry (PM), which contains abundant protein, was utilized as a raw material to coproduce XOS and single-cell protein (SCP) through autohydrolysis and fermentation technologies. Results: The results showed that 8.3 g of XOS and 1.8 g of amino acids could be recovered in the autohydrolysate (based on 100 g raw material) after autohydrolysis (170 °C, 1 h). Moreover, 5.7 g of low-DP XOS along with 1.8 g of amino acids could be further obtained from the autohydrolysate after hydrolysis with endo-β-1-4-xylanase. In addition, 20.1 g of fermentable monosaccharides was recovered after hydrolyzing the autohydrolyzed PM with cellulase, which can be used to produce 4.8 g of SCP after fermentation with Candida utilis. Conclusion: As a valuable application of PM, a novel process is proposed to coproduce amino acid-rich XOS and SCP through autohydrolysis. The carbohydrate of PM is effectively converted to high value-added products. [ABSTRACT FROM AUTHOR]

Eucalyptus regnans wood samples were treated with water under diverse conditions, in order to obtain soluble hemicellulose-derived products. The composition of the liquid phase from the treatment leading to the best results was characterized in depth using a combination of spectrophotometric, spectrometric and chromatographic methods; and the susceptibility of the treated solids to further fractionation by organosolv delignification was assessed in additional experiments. The chemical and physicochemical properties of the resulting lignin were determined, and the suitability of the delignified solids as substrates for the one-pot manufacture of ethyl levulinate was evaluated on a quantitative basis. [ABSTRACT FROM AUTHOR]

The integration of processes offers promising avenues for valorization of the tobacco waste, enabling the production of commercially significant compounds beyond traditional tobacco leaves designation. This research delves into the feasibility of extracting xylo-oligosaccharides (XOS) from tobacco stems via hydrothermal pretreatment. Emphasis was laid on XOS release kinetics from high solid loads (20% w/v) during pretreatment. The optimal conditions, which facilitated maximum oligomer recovery with minimal degradation compounds and reducing sugar solubilization, were then scaled up. The resultant solid fraction underwent enzymatic hydrolysis at varied solid loads (5%, 10%, and 15% w/v). Subsequent to this, succinic acid production was targeted, propelling the optimal enzymatic hydrolysate towards fermentation using the bacterium Actinobacillus succinogenes. Key findings revealed that a temperature of 190 °C during 8-min emerged as the most effective pretreatment conditions, yielding XOS at 49.54% with a concentration of 11.11 g.L−1. Enzymatic hydrolysis remained relatively uninfluenced by variations in solid loads, thereby permitting the use of high solid loads (15% w/v) to obtain concentrated hydrolysates at 49.37 g.L−1 with a conversion yield of 62.90%. Markedly, this study pioneered the demonstration of tobacco waste as a viable precursor for biosuccinic acid synthesis. Succinic acid concentration stood at 16.88 g.L−1, achieving a yield of 42%. A comprehensive mass balance evaluation spotlighted the potential to derive 56 kg of XOS and 78 kg of succinic acid per 1000 kg of tobacco raw biomass by the process developed herein. [Display omitted] • Hydrothermal pretreatment was effective in the fractionation of lignocellulose. • High solid concentration and retention time below 10 min enable XOS yield of 50%. • Enzymatic hydrolysis yielded 60% glucose with high solids load and low enzyme load. • Succinic acid yield of 0.42 g/g and productivity of 1.54 g/L/h were achieved. [ABSTRACT FROM AUTHOR]

It was proposed that pre-hydrolysing tule (Typha domingensis Pers) would make it possible to produce handsheets with strength-related properties similar to those of conventional commercial paper, in addition to valorizable hemicelluloses. The hypothesis was tested with a biorefining scheme involving autohydrolysis. Conditions were optimized to maximize the extraction of hemicelluloses while preserving glucan integrity. The autohydrolysis at a liquid to solid ratio of 13 at 141 °C for 45 min (optimized conditions) provided a commercially useful liquor containing primarily tule hemicelluloses. The autohydrolysis of tule before alkaline extraction made it possible to obtain a valuable liquid phase comprising between 23.3% and 71.6% of all hemicelluloses in the raw material. The gross heating value for the hydrolyzed tule was increased (1.6% to 7.9 %) with respect the raw material. The solid phase was subjected to soda-anthraquinone pulping. The yield, ethanol extractives, kappa number, viscosity, glucan, xylan, Klason lignin, soluble lignins, as well as the tensile index were evaluated. Tule was found to be amenable to industrial processing for the production of quality cellulose derivatives. Autohydrolysis provided valorizable liquor in addition to solid that yielded soda-anthraquinone pulp having properties similar to those obtained in its absence, but using milder operating conditions. [ABSTRACT FROM AUTHOR]

A combination of biorefinery processes (hydrothermal and membrane processing) was per- formed for the manufacture of oligosaccharides and natural phenolic compounds from poplar hemicelluloses. Both, oligosaccharides and phenolics have multiple potential appli- cations related to their bioactive properties. Firstly, non-isothermal autohydrolysis of poplar was performed to obtain oligosaccharides from the hemicellulosic fraction, while cellulose and lignin remained almost unaltered in the spent solid allowing their valorization in fur- ther processing stages. Operating at 210°C and liquid to solid ratio of 6 kg/kg, solutions containing 28.71 g oligosaccharides/L were obtained. Secondly, membrane refining of the resulting solution and further freeze-drying resulted in a product with high purity (90 kg of substituted oligosaccharides/100 kg of non-volatile compounds). The yield of substituted oligosaccharides in the target product accounted 16.6 kg/100 kg of poplar wood. Product characterization was accomplished by HPLC, HPSEC, HPAEC-PAD and MALDI TOF-MS. The data confirmed the presence ofbackbones containing up to DP13 pentose units, with a complex substitution pattern by acetyl groups and 0-methyl-uronic moieties. Additionally, the presence of natural phenolic compounds bounded to oligosaccharides conferred antioxidant properties to the target product. Substituted oligosaccharides and phenolics are postulated as valuable products with interest in food and pharmaceutical industries. [ABSTRACT FROM AUTHOR]

Background: Soil-derived exogenous ash (EA) poses a challenge toward lignocellulosic autohydrolysis due to its buffering capacity. Previous works focusing on this phenomenon have failed to also investigate the role that soluble salts, and organic matter plays in this system. Herein, sodium phosphate and sodium humate were employed as model buffering compounds representing soluble salts and organic matter and dosed into a de-ashed wheat straw (DWS) autohydrolysis process to show the potential impacts of WS attached soil conditioners on the WS autohydrolysis efficiency which would further affect the enzymatic digestibility of autohydrolyzed WS. Results: Results showed that with the increasing loadings of sodium phosphate and sodium humate resulted in elevated pH values (from 4.0 to 5.1 and from 4.1 to 4.7, respectively). Meanwhile, the reductions of xylan removal yields from ~ 84.3–61.4% to 72.3–53.0% by loading (1–30 g/L) sodium phosphate and sodium humate during WS autohydrolysis lead to a significant decrease of cellulose accessibilities which finally lead to a reduction of the enzymatic digestibility of autohydrolyzed WS from ~ 75.4–77.2% to 47.3–57.7%. Conclusion: The existence of different types soil conditioner model compounds results in various component fractions from autohydrolyzed WS in the process of autohydrolysis. A lack of sufficient xylan removal was found to drive the significant decrease in enzymatic accessibility. The results demonstrated the various effects of two typical tested soil conditioners on WS autohydrolysis and enzymatic hydrolysis. [ABSTRACT FROM AUTHOR]

Eucalyptus sawdust is a residue from the pulp industry, currently used for energy production. Organosolv and autohydrolysis pretreatments for integrated valorization of this residue within a biorefinery approach was investigated. Organosolv pretreatment was used for selectively extract lignin, and autohydrolysis pretreatment was effective for hemicellulose solubilization. Glucose production of 33.7 g/100 g eucalyptus was achieved after organosolv pretreatment, while dissolving 6.4 g/100 g eucalyptus of xylan-derived sugars and recovering 10.3 g/100 g eucalyptus of lignin after precipitation. After autohydrolysis pretreatment, glucose production of 32.3 g/100 g eucalyptus was reached, while 7.5 g/100 g eucalyptus of xylan-derived sugars and 2.7 g/100 g eucalyptus of acetyl groups were effectively dissolved in a separate liquid stream. Non-ionic surfactant (PEG 6000) was used to enhance cellulose hydrolysis. Integration of a suitable pretreatment and enzymatic hydrolysis steps was shown to be a feasible strategy for the co-production of different value-added products (lignin, xylose, xylo-oligomers, acetic acid), towards a cost-effective eucalyptus biorefinery. • Pretreatments were conducted under mild conditions for total utilization of biomass. • Organosolv pretreatment recovered almost 40% of lignin in eucalyptus sawdust. • Enzymatic hydrolysis of pretreated substrates yielded up to 82% of glucan to glucose. • PEG 6000 weakened the negative effect of lignin on cellulose enzymatic hydrolysis. • The proposed biorefinery scheme achieved an integral use of eucalyptus sawdust. [ABSTRACT FROM AUTHOR]

Herein, cellulose nanocrystals were synthesized from oil palm fronds (CNC-OPF) involving two pretreatment approaches, viz. autohydrolysis and soda pulping. The pretreatments were applied individually to OPF fibers to assess their influence on CNCs' physicochemical and thermal properties. CNC-OPF samples were assessed using complementary characterization techniques, which confirmed their purity and characteristics. CP/MAS 13C NMR and TEM studies revealed that autohydrolysis pretreatment yielded CNCs with effective hemicellulose and extractives removal compared to that of soda pulping. XRD analysis demonstrated that autohydrolysis-treated CNC-OPF contained a much higher crystallinity index compared to soda pulping treatment. BET measurement disclosed a relatively higher surface area and wider pore diameter of autohydrolysis-treated CNC-OPF. Autohydrolysis-treated CNCs were applied as a reinforcement filler in alginate-based hydrogel beads for the removal of 4-chlorophenol from water, which attained a q max of 19.168 mg g−1. BET analysis revealed the less porous nature of CNC-ALG hydrogel beads which could have contributed to hydrogel beads' relatively lower adsorption capacity. The point of zero charge of CNC-ALG hydrogel beads was 4.82, suggesting their applicability only within a short solution pH range. This study directs future studies to unveil the possibilities of functionalizing CNCs in order to enhance the adsorption performance of CNC-immobilized hydrogel beads towards 4-chlorophenol and other organic contaminants. [Display omitted] • Autohydrolysis and soda pulping pretreatments were assessed to characterize CNC-OPF. • Autohydrolysis yielded CNC-OPF with enhanced physicochemical and thermal properties. • Autohydrolysis-treated CNC-OPF were reinforced to prepare alginate-based beads. • OPF-derived CNC-alginate hydrogel beads revealed potential 4-CP adsorption capability. [ABSTRACT FROM AUTHOR]

Two previous treatments have been applied to the ethanol-soda paste process on Eucalyptus globulus wood to evaluate its influence on the properties of the obtained cellulose pulps. The treatments consisted of a first optimized stage of autohydrolysis (temperature: 180 °C, time: 30 min) to obtain the maximum extraction rate of hemicellulosic derivatives preserving the glucan, followed by enzymatic oxidative delignification by a laccase/mediator system (syringaldehyde). Experimental designs have been applied for the optimization of processes. The optimum operating conditions in the enzymatic delignification stage were: Lacasse concentration 18,5 U/g, concentration of syringaldehyde 1,5 %, temperature 45 °C and operating time 60 min., with which an elimination of the 16,8% of the existing lignin in the raw material and slightly affects the glucan (it is conserved between 82,2 % and 89,7 % of the initial glucan). Two liquid, recoverable phases are obtained, rich in hemicellulose and polyphenolic derivatives. In this process scheme to obtain ethanol-soda cellulosic pulp from eucalyptus wood requires a lower concentration of chemical reagents, shorter operating times and lower temperatures, which is an economic and environmental improvement over the conventional pulping process. [ABSTRACT FROM AUTHOR]

Biorefining uses alternative resources (such as biomass) instead of petrochemical sources to produce bioenergy and platform chemicals. Walnut shell is a promising lignocellulosic biomass for the production of fermentable carbohydrates. In this study, the platform chemical L-(+) lactic acid was produced after walnut shell had been treated with physicochemical and biological processes. So biomass waste can be regenerated to the benefit of the circular bio-economy. Autohydrolysis assisted by microwave processes was used to depolymerize hemicellulose and amorphous cellulose in walnut shell to yield 63.5% w/w of xylose in a liquid fraction (hydrolysate) with a minimum yield of glucose. The optimum reaction conditions to obtain a high xylose yield with a low byproduct titer were 190 °C for 25 min. L-(+) lactic acid was produced by thermophilic Bacillus coagulans DSM 2314 with a carbon source of xylose and glucose which were solubilized in hydrolysate from autohydrolyzed walnut shell. A non-sterile and straightforward fermentation medium coupled with a pH adjustment of the crude hydrolysate in an anaerobic environment led to a L- (+) lactic acid yield of 81% w/w with a productivity of 0.2 g/L/h. Image 1 • Autohydrolysis assisted by microwave processes depolymerized hemicellulose. • Both physical and chemical impacts were revealed after autohydrolysis. • By-products in hydrolysate did not affect fermentation process. • 63.5 wt% of xylose yield was obtained from walnut shell's hemicellulose component. • Bacillus coagulans converted xylose and glucose into L- (+) lactic acid. [ABSTRACT FROM AUTHOR]

This study presents for the first time results on hydrothermal treatments (autohydrolysis) of cork to assess their chemical effect on its structural components, namely on suberin. Extractive-free cork was autohydrolysed in isothermal conditions with a broad range of severity factors (SF) of 2.1–4.7 (120–180 °C, 60–240 min) determining mass loss and chemical changes in cork, namely on suberin content and composition. Mass loss was small for milder conditions, and increased steadily with severity e.g. 4.0% for SF 3.0, 9.8% for SF 3.8, 14.1% for SF 4.6. However, mass loss of cork by autohydrolysis is much smaller than that of lignocellulosic biomass under comparable treatment severity. Until SF 3.0, little chemical changes were seen, with SF 3.3–4.1, the autohydrolysed cork showed higher dichloromethane (DCM) solubles and suberin, and less polysaccharides, while for the most severe conditions (SF 4.4–4.7), there was a substantial increase of DCM solubles, a downfall in suberin and polysaccharides, and an unaltered lignin content. Cork polysaccharides decreased steadily with SF increase by hydrolysis of hemicelluloses, e.g. 7.1% of cork for SF 3.5% and 3.9% for SF 4.7. Suberin was maintained in cork until SF 4.4 without changes in composition, but decreased subsequently e.g. at SF 4.7, suberin represented 47% of the initial untreated cork (56% in the initial cork) and showed less ω -hydroxy acids and more α,ω -diacids. The amount and composition of suberin and DCM solubles in the autohydrolysed cork under the various reaction severities allow concluding that suberin is stable until 160 °C but depolymerizes at higher temperatures by ester bond cleaving mostly of mono-functional long-chain monomers. Overall cork showed higher hydrothermal stability than lignocellulosic materials. ● Cork is resilient to autohydrolysis and mass loss is very small for mild conditions. ● Hemicelluloses are the most hydrothermal sensitive cork structural components. ● Suberin is chemically resistant under mild autohydrolysis until 160 °C. ● 18% suberin depolymerization occurred in the severest conditions (180 °C, 240 min). ● Carboxylic acids and α,ω - diacids are, respectively, most and less sensitive to hydrolysis. [ABSTRACT FROM AUTHOR]

The extraction of hemicellulose from pine wood was studied by applying autohydrolysis treatment. A central composite experimental design was carried out using different temperatures (150–190 °C) and times (30–90 min) to select the most favorable operating conditions for maximizing the extraction of hemicellulose and minimizing its degradation. This liquid phase was analyzed by HPLC to quantify oligosaccharides, monosaccharides and degradation products. The composition of the autohydrolyzed wood was determined and characterized, employing FTIR and TGA. Herein, 60% of the hemicelluloses were extracted under a temperature of 170 °C in 60 min, presenting primarily in an oligomeric form in the liquid phase, with the solid phase remaining enriched in cellulose and lignin. [ABSTRACT FROM AUTHOR]

Hydrothermal treatment is an environmentally friendly technology that allows the solubilisation of hemicellulosic oligosaccharides with potential for their use as prebiotics. The purpose of this study was to solubilize oligosaccharides and antioxidant compounds from chestnut shells by a hydrothermal processing. The highest content of oligosaccharides (18.3 g/L), with a relatively low level of monosaccharides (2.4 g/L) and degradation products (0.5 g/L) was obtained at 180 °C (severity of 3.08). In addition, the liquors presented a high content of phenolic and flavonoid compounds with good antioxidant properties. The GC–MS revealed that the most abundant phenolic compound was pyrogallol (13.2%). The molecular weight distribution of the solubilization products showed that a 26.5% presented an apparent Mw of 6077 g/mol and a 73.5% presented an apparent Mw of 586 g/mol with a high polydispersity index. MALDI-TOF, FTIR, and TGA analyses revealed structural information of these compounds and their thermal stability. [ABSTRACT FROM AUTHOR]

Peanut shells were subjected to non-isothermal aqueous treatments to cause the partial breakdown of hemicelluloses into soluble oligosaccharides and lignin-derived compounds with high antioxidant activity. The effects of temperature on the chemical composition of the substrate and soluble reaction products were assessed. Under selected conditions (210 °C, severity = 4.09), the overall amount of poly- and oligo- saccharides present in the liquid phase reached 9.8 g/L. This solution was refined by consecutive stages of discontinuous diafiltration, yielding a refined product containing about 72.4 wt% of oligomers at a global yield of 8.5 kg/100 kg oven-dry PS. The purified products were characterized by HPLC, MALDI-TOF-MS and FTIR, confirming the major reaction products were saccharides made up of xylose with degrees of polymerization up to 17, substituted with acetyl and methylglucuronosyl groups, for which a number of pharmaceutical and food applications have been proposed. Solubilization of hemicelluloses in the treatments resulted in the production of solids enriched in cellulose and lignin suitable for further applications. [ABSTRACT FROM AUTHOR]

This study dealt with the use of environmentally friendly processes based on microwave-assisted autohydrolysis (MAA) and deep eutectic solvents (DES) for the selective fractionation of Robinia pseudoacacia wood (RW) within a biorefinery approach. MAA enabled the recovery of 76% of hemicelluloses in the form of oligomers. Afterwards, different conditions were assessed for the optimal delignification of RW with the DES choline chloride combined with lactic acid reaching delignification ratios up to 86%. Two different methods were accomplished to valorize the cellulosic-rich solid fraction after delignification: (i) bioethanol via enzymatic-fermentative pathway (attaining 53.3 g ethanol/L, about 83% of ethanol yield), and (ii) cellulose nanocrystals (length of 27–550 nm, width of 2–12 nm). Hence, this study presents a novel multiproduct biorefinery to selectively separate the main components of RW and valorize its cellulosic fraction using eco-friendly procedures. • A green multi-product biorefinery was proposed to valorize Robinia wood (RW). • Microwave-assisted autohydrolysis solubilized up to 76% of oligomers from RW. • Up to 86% of lignin was solubilized using deep eutectic solvents. • Ethanol yield of 83% (53.3 g/L) was achieved from processed RW. • Cellulose nanocrystals with high length/diameter ratio (41.21) were produced. [ABSTRACT FROM AUTHOR]

The aim of this work was to compare the two most common hydrothermal pre-treatments for wood – mild steam explosion and hot water extraction – both with the prospect of enabling extraction of hemicelluloses and facilitating further processing. Although both involve autohydrolysis of the lignocellulosic tissue, they are performed under different conditions: the most prominent difference is the rapid, disintegrating, discharge employed in the steam explosion opening up the structure. In this comparative study, the emphasis was placed on local composition of the pre-treated wood chips (of industrially relevant size). The results show that short hot water extraction treatments lead to significant variations in the local composition within the wood chips, while steam explosion accomplishes a comparably more even removal of hemicelluloses due to the advective mass transport during the explosion step. [ABSTRACT FROM AUTHOR]

Sugarcane bagasse, the major by-product of the sugarcane industry, can be used to produce valuable materials such as cellulose or cellulose-based materials. In order to obtain more accessible and purified cellulose, pretreatment processes of lignocellulosic feedstocks are applied to decompose the complex cellulose-lignin-hemicellulose matrix, which facilitates access to isolated compounds. The influence of various autohydrolysis conditions, alkaline sulfite extraction and bleaching were evaluated in terms of extract yield, chemical profile and structural properties upon a solid fraction rich in cellulose. Among the treatments applied, autohydrolysis at 170 °C for 1 h followed by a bleaching step was the treatment that presented the best results in terms of cellulose purity (77.8%), crystallinity (73.4%), whiteness and glucose production by enzymatic hydrolysis, when compared with the non-treated fraction. The combination of autohydrolysis with a totally chlorine free bleaching step showed as a promising eco-friendliness alternative to obtain a white and solid fraction rich in cellulose, thus contributing to the valorization of this by-product. [Display omitted] • Autohydrolysis at 170 °C yielded 63.5% of a solid fraction with 69.4% of cellulose. • Alkaline sulfite at 180 °C yielded 50.9% of a solid fraction with 72.1% cellulose. • Bleaching was essential to obtain whiter and purer cellulose fractions. • Autohydrolysis at 170 °C followed by bleaching proved to be the most effective process. • Simple and effective process to obtain high purity cellulose fractions from SCB. [ABSTRACT FROM AUTHOR]

To assess the feasibility of implementing hemicellulose recovery stages in kraft mills, Eucalyptus globulus wood samples were subjected to aqueous treatments with hot, compressed water (autohydrolysis processing) to achieve partial dissolution of xylan. Autohydrolyzed solids were subjected to kraft pulping under selected conditions to yield a pulp of low kappa number, and to an optimized TCF bleaching sequence made up of three stages (alkaline oxygen delignification, chelating, and pressurized hydrogen peroxide), with minimized additions of pulping and bleaching chemicals. The final product had a relatively low kappa number (1.4), 641 mL/g ISO intrinsic viscosity, and 86.4% brightness.

Rapeseed straw consists of a hard epidermis that is rich in hemicellulose and lignin and a sponge-like interior that consists mainly of cellulose. The stems were subjected to water, alkali or acid as extraction medium. The effects of the extraction conditions were quantified using severity factors and by comparing the effects of different extraction pHs, temperatures and times. Extraction with alkali resulted in a higher yield, 47 g/100 g straw in, compared to water, 6 g/100 g straw in, or an acidic, 5 g/100 g straw in, extraction process. An increase in temperature improved the extraction yield; in particular, more xylan was extracted at an elevated temperature and higher alkalinity. However, at high alkalinity, increased extraction temperatures led to a reduction in the recovery of glucomannan. The highest molecular weights (∼35,000 g/mol) of the extracted hemicelluloses were obtained using extraction procedures with 1.5 M NaOH at 110 °C and autohydrolysis at 150 °C. While these two parameter settings had very similar severity factors, extraction under basic conditions afforded an extract rich in xylan and low in lignin content, whereas autohydrolysis generated a glucomannan-rich extract. [ABSTRACT FROM AUTHOR]

This work is aimed at investigating the influence of changes in the content of hemicelluloses of the autohydrolyzed poplar sapwood on the subsequent alkali impregnation for chemi-mechanical pulping (CMP). An alkali impregnation process was conducted using the autohydrolyzed poplar sapwood with different content of hemicelluloses as raw materials. The results showed that both the amount of NaOH consumption and swelling degree of poplar sapwood increased with the removal of hemicelluloses, thus enhancing the alkali impregnation effectiveness. The hemicelluloses removal can also shorten the alkali impregnation time for the autohydrolyzed poplar sapwood to achieve the similar impregnation effectiveness of unautohydrolyzed poplar sapwood. All of these can be attributed to the fact that the hemicelluloses removal would result in the exposure of more free hydroxyl groups on the cellulose and an increase in the porosity of the fiber cell walls. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate strategies of detoxification and fermentation of the hemicellulosic liquors obtained from sugarcane bagasse autohydrolysis, for the biotechnological production of xylitol. Different sequences of detoxification treatments were performed, and their effects on sugars loss and inhibitors removal were evaluated. Fermentation assays were accomplished with commercial xylose to select the best yeast ( C. guilliermondii , C. tropicalis ) and the fermentation conditions of the detoxified spent liquors. Detoxification through a sequence of treatments, including Ca(OH) 2 , IR-120 resin, activated charcoal, and IRA-67 resin, practically removed all inhibitors from the hemicellulosic spent liquors. Maximal concentration of xylitol obtained was 32.0 g L −1 ( C. tropicalis , xylose: 104.1 g L −1 , yield: 0.46 g g −1 , productivity: 0.27 g L −1 h −1 ). The technological parameters to obtain a detoxified spent liquor rich in xylose and its bioconversion to xylitol were determined. [ABSTRACT FROM AUTHOR]

Background: During pretreatment, hemicellulose is removed from biomass via proton-catalyzed hydrolysis to produce soluble poly- and mono-saccharides. Many kinetic models have been proposed but the dependence of rate on proton concentration is not well-defined; autohydrolysis and dilute-acid hydrolysis models apply very different treatments despite having similar chemistries. In this work, evolution of proton concentration is examined during both autohydrolysis and dilute-acid hydrolysis of hemicellulose from green bamboo. An approximate mathematical model, or "toy model", to describe proton concentration based upon conservation of mass and charge during deacetylation and ash neutralization coupled with a number of competing equilibria, was derived. The model was qualitatively compared to experiments where pH was measured as a function of time, temperature, and initial acid level. Proton evolution was also examined at room temperature to decouple the effect of ash neutralization from deacetylation. Results: The toy model predicts the existence of a steady-state proton concentration dictated by equilibrium constants, initial acetyl groups, and initial added acid. At room temperature, it was found that pH remains essentially constant both at low initial pH and autohydrolysis conditions. Acid is likely in excess of the neutralization potential of the ash, in the former case, and the kinetics of neutralization become exceedingly small in the latter case due to the low proton concentration. Finally, when the hydrolysis reaction proceeded at elevated temperatures, one case of nonmonotonic behavior in which the pH initially increased, and then decreased at longer times, was found. This is likely due to the difference in rates between neutralization and deacetylation. Conclusions: The model and experimental work demonstrate that the evolution of proton concentration during hydrolysis follows complex behavior that depends upon the acetyl group and ash content of biomass, initial acid levels and temperature. In the limit of excess added acid, pH varies very weakly with time. Below this limit, complex schemes are found primarily related to the selectivity of deacetylation in comparison to neutralization. These findings indicate that a more rigorous approach to models of hemicellulose hydrolysis is needed. Improved models will lead to more efficient acid utilization and facilitate process scale-up. [ABSTRACT FROM AUTHOR]

Birch samples were subjected to non-isothermal autohydrolysis to obtain a solution of hemicellulosic saccharides and a solid phase mainly made up of cellulose and lignin. Based on kinetic modeling, operational conditions were identified which give rise to soluble saccharides and furfural derived from xylan in a yield of 80.5%. The soluble mixture was supplemented with 1% sulfuric acid and heated (directly or in the presence of methyl isobutyl ketone, MIBK) for furfural production. MIBK is used as an extraction agent to limit furfural consumption by side reactions. Operating in single phase at 170°C, up to 44.8% of the potential substrates were converted into furfural. In experiments performed in biphasic media, the effects of MIBK were assessed by empirical modeling and about 75% of the potential substrates were converted under selected conditions. [ABSTRACT FROM AUTHOR]

Agricultural feedstocks (brewers’ spent grain – BSG, corncob – CC, corn husk – CH, wheat straw – WS and Luffa sponge – LS) were pretreated by liquid hot water (LHW) in order to increase cellulose recovery and enzymatic saccharification. LHW-pretreatment resulted in hemicellulose solubilization, and solids enriched in cellulose. Chemical analysis showed different susceptibilities of the feedstocks to LHW-pretreatment and enzymatic hydrolysis. Pretreated feedstocks presented higher crystallinity (determined through X-ray diffraction) and thermal stability (determined through thermogravimetric analysis) than untreated feedstocks. SEM images confirmed the effect of LHW-pretreatment on structural changes. Moreover, enzymatic hydrolysis and cellulose conversion to glucose (CCG) were improved for pretreated feedstocks, with exception of LS. CCG (in relation to glucose potential on solids) followed the order: BSG > CH > WS > CC > LS. LHW-pretreatment showed to be a good technology to pretreat multi feedstocks and for improving the enzymatic hydrolysis of recalcitrant agricultural feedstocks to sugars, which can be further converted to ethanol-fuel and other value-added chemicals. [ABSTRACT FROM AUTHOR]

Vine shoots were subjected to non-isothermal aqueous processing. A range of severities ( S 0 ) from 3.20 to 4.65 was assayed and their effects in terms of solubilization, composition, molar mass distribution, structural characterization and thermal stability of the liquors were studied using HPLC, HPSEC, TGA and FTIR. The spent solids were characterized by HPLC and FTIR. When autohydrolysis was carried out at S 0 = 4.01, the substrate solubilization achieved a 38.7% of the raw material and 83.1% of the initial xylan was converted into xylooligosaccharides (XOS). The amount of TOS (total oligosaccharides) in the hydrolysates was 28.4 g/L while the other non volatile compounds (ONVC) were 0.08 g/g NVC. The spent solid from the treatment at S 0 = 4.01 was composed about 90% of cellulose and lignin. Therefore, it can be concluded that autohydrolysis is a suitable pretreatment of vine shoots such as a first stage of a biomass refinery. [ABSTRACT FROM AUTHOR]

Residual woody biomass from wood processing factories is commonly used as raw material for energy purposes. However, special attention is being paid to the development of biorefining systems based on lignocellulosic materials to produce high-added value bioproducts such as soluble saccharides of polymeric and oligomeric nature (POHs), cellulose, lignin, antioxidant extracts, levulinic acid or formic acid. In this study, four different potential valorisation scenaria from residual woody chips were assessed and compared from an environmental perspective using the Life Cycle Assessment methodology (cradle-to-gate approach) in order to identify the most sustainable biorefining route. Differences on these scenaria were based on different extraction routes considering always the same raw material and based on protocols performed at semi-pilot scale by the authors: two of them were mainly focused on POHs production and the remaining two, on levulinic acid. According to the results obtained, those scenaria focused on levulinic acid production reported the worst environmental performances due to the acidic treatment performed regardless the functional unit selected. Among the processes considered, purification (concentration + freeze-drying) and saccharide conversion (post-autohydrolysis) related activities were the major responsible of environmental burdens in the POHs and levulinic acid production routes, mainly due to the large energy requirements. In addition, differences on the behaviour of environmental profiles on the scenaria based on levulinic acid production were also identified regarding the functional unit considered. Accordingly, the introduction of an additional purification step for the recovery of an antioxidant extract implied higher environmental impacts when a functional unit is based on the amount of valorised biomass. In contrast, lower environmental burdens should be obtained if the economical based functional unit is considered. Therefore, the outcomes of the LCA study were highly dependent on the production yield of the target compounds and the protocols followed. Further research should be focused on the improvement of the extraction techniques due to the large energy and chemical requirements. LCA results could be considered as a usefulness tool for decision making strategies, specifically in biorefining systems under development. [ABSTRACT FROM AUTHOR]

The operating conditions for the autohydrolysis of eucalyptus wood were optimized with a view to maximizing hemicellulose extraction while preserving the integrity of glucan. The influence of the operating conditions used in the soda–anthraquinone pulping of the solid phase resulting from the autohydrolysis process was examined. Autohydrolysis of the raw material at a liquid/solid ratio of 8 kg water/kg material at 180°C for 30 min was found to provide a commercially useful liquid phase containing most of the starting hemicellulose. The autohydrolysis treatment allowed the subsequent production of soda–anthraquinone cellulose pulp and paper with properties as good as or even better than those obtained without the pretreatment. [ABSTRACT FROM PUBLISHER]

Microwave-assisted autohydrolysis is an environmentally friendly intensification technology that permits the selective solubilization of hemicelluloses in form of oligosaccharides in a short time and with low energy consumption. The purpose of this work was to evaluate the suitability of microwave-assisted autohydrolysis to produce oligosaccharides and phenolics with potential prebiotic and antioxidant activities from Robinia pseudoacacia wood. The influence of treatment time (0–30 min) and temperature (200–230 °C) on oligosaccharide production was studied and conditions of 230 °C and 0.25 min resulted in maximum content of xylooligosaccharides (7.69 g XO/L) and more efficient energy consumption. Furthermore, under those conditions, liquors showed high contents of phenols (80.28 mg GAE/g of RW) and flavonoids (44.51 RE/g) with significant antioxidant activities (112.07 and 102.30 mg TE/g, measured by ABTS and FRAP tests, respectively). Additionally, the solubilized hemicelluloses were structurally characterized by HPAEC-PAD, MALDI-TOF-MS, FTIR and TGA/DSC, and HPLC-ESI-MS analysis allowed the tentative identification of 17 phytochemicals. [Display omitted] [ABSTRACT FROM AUTHOR]

Polymeric hemicelluloses were extracted by autohydrolysis and alkali from a biomass feed consisting of the stems of rapeseed straw according to a full statistical factorial screening design. Water extraction yielded fractions rich in galactoglucomannan, while alkaline extraction yielded primarily xylan. The extracted galactoglucomannan and xylans had similar molecular weights, while the yield of xylan was higher than the yield of galactoglucomannan. The extracted hemicellulose fractions also contained some lignin (7–15%) and traces of Ca, K, Na, and Si. Free-standing films were prepared from the hemicellulose fractions with different xylan:galactoglucomannan ratios. The rapeseed xylan films showed strain-to-break values >60% without any added plasticizers. [ABSTRACT FROM AUTHOR]

Subcritical water extraction is one of the green ways to isolate plants biomass components. In this work, it has been applied as a media to extract β-glucan from barley ( Hordeum vulgare L.). The extractions were carried out at temperatures of 130–170 °C and a pressures of 10–40 MPa, using a semi-batch system. UV–vis spectra of liquid fraction products showed a high content of hemicelluloses, including glucan compounds. Results of FT-IR spectra analysis showed that β-glucan has been extracted from barley grains after subcritical water treatment. The elemental analysis showed that dehydration and decarboxylation occurred during subcritical water extraction of barley grains at these conditions. The gel permeation chromatography (GPC) analysis showed that the average molecular weight of water-soluble products were approximately 500 Da to 1167 kDa. To improve the extraction process, the CO 2 was added. At the same extraction time, the yield of β-glucan in the liquid fraction products increased clearly with the presence of CO 2 . [ABSTRACT FROM AUTHOR]

The autohydrolysis process as a method for selective extraction of hemicelluloses and conversion to furfural was proposed for lignocellulosic raw materials. Samples of wheat straw (WS) and Eucalyptus globulus (EG) were subjected to nonisothermal autohydrolysis, defined by temperature 180-240°C. Within a biorefinery scheme for the selected materials, the aim of this study is both (a) to optimize furfural processing technology to enable higher yields and improved productivity from EG and WS by autohydrolysis and (b) to not excessively degrade the remaining polymeric constituents (glucan) in solid to facilitate a potential later use. Differences in the rate of the dehydration reaction of xylose to furfural have been observed, and it is faster in the case of WS with respect to that observed for eucalyptus. In that form, 4.25 g/100 g raw material (26% of the initial xylan in WS) could be found at 220°C, and an increase in the temperature (240°C) yielded 4.54 g/100 g raw material, 28% of the initial xylan. In EG, the increase in the hydrolysis temperature (240°C) yielded liquor with higher contents of furfural (4.45 g/100 g raw material, 25% of the initial xylan) and acetic acid (4.49 g/100 g raw material) and smaller contents of arabinose and xylan. In WS, a faster dehydration is found. © 2015 American Institute of Chemical Engineers Environ Prog, 34: 1236-1242, 2015 [ABSTRACT FROM AUTHOR]

The autohydrolysis process has been considered a simple, low-cost and environmental friendly technology for generation of sugars from biomass. In order to improve accessibility of enzymes during enzymatic hydrolysis as well as to allow the recovery of hemicellulose in the filtrate, the sugarcane bagasse was pretreated using autohydrolysis followed by a mechanical refining process. The autohydrolysis was carried out in three different conditions. Autohydrolysis at 190 °C for 10 min provided the highest overall sugar (19.2/100 g raw bagasse) in prehydrolyzate. The enzymatic hydrolysis step was performed for all the post-treated solids with and without refining at enzyme loadings of 5 and 10 FPU/g for 96 h. A total of 84.4% of sugar can be recovered from sugarcane bagasse at 180 °C for 20 min with 5 FPU/g enzyme charge. The economic analysis for the proposed method showed that the bioethanol production can have a financial return larger than 12%. [ABSTRACT FROM AUTHOR]

This study investigates the operating conditions used in the sodaanthraquinone pulping of Eucalyptus globulus wood after autohydrolysis pretreatment on the yield, kappa number, and brightness of the resulting unbleached pulp. Moreover, strength-related properties of the resulting handsheets was examined to identify the best pulping conditions and compare the outcome with that of a conventional soda-anthraquinone pulping process. The paper strength properties of the pulp were similar to or better than papers made from soda-AQ delignified pulps conducted in a single step. Also, a liquid fraction with a substantial content in hemicellulosic extracts was recovered in the simplified process. Autohydrolysis of the raw material facilitates carrying out soda-AQ pulping under milder conditions. In addition, autohydrolysis improves other properties relative to paper from raw cellulose pulp. Yield, kappa number, and brightness for pulp from solid residues of autohydrolysed eucalyptus wood were similar to those for pulp from untreated eucalyptus wood. [ABSTRACT FROM AUTHOR]

Hydrothermal treatment (autohydrolysis) is an advantageous alternative to fractionate biomass that was not yet explored for rice straw. In this work, the process was optimised and proved to be highly selective towards hemicellulose. Hydrolysates containing a mixture of oligomeric compounds (mainly xylo-oligosaccharides, XOS), could be obtained under relatively mild operation conditions (210 °C, log R 0 = 3.59), yielding a maximum of 40.1 g/100 g of initial xylan. The produced XOS were separated by molecular mass using gel filtration chromatography (GFC). Different fractions of purified XOS were obtained ranging from small polysaccharides and high DP oligosaccharides (DP ≥23), to medium and low DP oligosaccharides (DP ≥3), and separated fractions of by-products (acetic acid, furan derivatives and phenols) as well as di-, and monosaccharides. GFC was an efficient purification method enabling the recovery of interesting categories of XOS that can have potential applications to the pharma, food and feed industries. [ABSTRACT FROM AUTHOR]

Hydrolysis to remove hemicellulose and/or generate saccharides is an integral unit operation for the production of chemicals, fuels, and materials from lignocellulosic biomass. Softwoods and bamboo are both widely available but comparatively understudied feedstocks. This paper first reviews the unique hemicellulose chemistry of these feedstocks and the fundamental mechanism of polysaccharide hydrolysis. The influence of temperature, time, acid concentration, particle size, and reactor configuration on water-only hydrolysis, or autohydrolysis, and dilute acid hydrolysis are summarized. The composition, molecular weight, and yields of saccharides and degradation products generated during hydrolysis are presented. Finally, the types, strengths, and weaknesses of current hemicellulose hydrolysis kinetic models are reviewed. © 2014 Society of Chemical Industry and John Wiley & Sons, Ltd [ABSTRACT FROM AUTHOR]

Wheat straw was subjected to three different processes prior to saccharification, namely alkaline pulping, natural pulping and autohydrolysis, in order to study their effect on the rate of enzymatic hydrolysis. Parameters like medium concentration, temperature and time have been varied in order to optimize each method. Milling the raw material to a length of 4 mm beforehand showed the best cost–value-ratio compared to other grinding methods studied. Before saccharification the pulp can be stored in dried form, leading to a high yield of glucose. Furthermore the relation of pulp properties (i.e. intrinsic viscosity, K lason -lignin and hemicelluloses content, crystallinity, morphology) to cellulose hydrolysis is discussed. [ABSTRACT FROM AUTHOR]

Steam explosion and steam pre-treatment have proved capable of enhancing enzymatic saccharification of lignocellulosic materials. However, until now, these methods had not been compared under the same operational conditions and using the same raw material. Both pre-treatments lead to increased yields in the saccharification of Eucalyptus globulus; but results have been better with steam pre-treatments, despite the more accessible surface of exploded samples. The reason for this finding could be enzymatic inhibition: steam explosion causes a more extensive extraction of hemicelluloses and releases a greater amount of degradation products which can inhibit enzymatic action. Enzymatic inhibition is also dependent on the amount and chemical structure of lignin, which was also a contributing factor to the lower enzymatic yields obtained with the most severe pre-treatment. Thus, the highest yields (46.7% glucose and 73.4% xylose yields) were obtained after two cycle of steam treatment, of 5 and 3 min, at 183 °C. [ABSTRACT FROM AUTHOR]