Search

Elephant grass is a promising lignocellulosic biomass for use in biorefineries due to its composition and productivity. To enhance the use of elephant grass (Pennisetum purpureum Schum.) as a raw material for the production of fermentable sugars, two different hydrothermal pretreatment methodologies were studied, using liquid hot water and saturated steam. Hydrothermal pretreatments were carried out according to a central composite design, varying the time (1–12 min) and temperature (170–220 °C) of the processes. Solid fractions were subjected to hydrolysis using the enzymatic complex produced by Pennicilium echinulatum. Both methodologies tested showed a strong positive linear correlation between the severity factor [logRo] of the pretreatments and the removal of hemicellulose, allowing a high recovery of cellulose in the solid fraction. In pretreatments with an intermediate severity factor, between 2.87 and 3.88, the liquid hot water pretreatment improved the enzymatic hydrolysis yield, in addition to presenting the best fractionation of hemicellulose and total glucose yield. However, at pretreatment severity factors equal to or greater than 4.30, saturated steam pretreatment allowed a greater increase in hydrolysis yield. The maximum enzymatic hydrolysis yield was 65.6 mol%, obtained in saturated steam pretreatment at 220 °C for 6.5 min, being 147 mol% higher than the yield of untreated elephant grass. Mathematical models describing the enzymatic hydrolysis yield as a function of time and temperature used in each pretreatment methodology are proposed. [ABSTRACT FROM AUTHOR]

Copyright of Chemistry & Industry of Forest Products is the property of Chemistry & Industry of Forest Products Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The leaves and petioles of Paulownia elongata x fortunei are residual fractions from the tree plantations commercially destined to the production of wood and their valorization could contribute to the rational utilization of this resource. The saccharidic fraction is the most abundant in both parts of the plant and the sugar profile is very similar, but the ethanol extractives are more abundant in leaves. Non isothermal processing was selected since it provided better results than isothermal extraction with shorter times. For this reason, optimization of autohydrolysis under non isothermal operation (140–240 °C) was performed for both materials: leaves and petioles. The final autohydrolysis temperature highly influenced the saccharidic, proteic, phenolic and volatile composition of the extracts. Operating under selected conditions leaves provided extracts with more antioxidant compounds than petioles. The proposed technology provides a variety of commercially valuable components, which could contribute to the integral use of this energetic crop following a biorefinery approach. [ABSTRACT FROM AUTHOR]

Pretreatment with efficient fractionation, eco‐friendliness, and low‐cost brings high security to future biorefinery systems. Synergistic pretreatment is a compelling blueprint to tackle the compact structure of lignocellulose towards a high‐level valorization. Here, a stepwise approach was designed using hydrothermal and deep eutectic solvent (DES) pretreatments to hierarchically extract hemicelluloses and lignin from poplar, while delivering a cellulose‐rich substrate that could easily undergo enzymatic hydrolysis to obtain fermentable glucose and residual lignin. The lifetime of recyclable DES showed that the pretreatment efficiency was still largely maintained after the fourth recycling. An enhancement of enzymatic digestibility from 13.9 to 90.4 % was initiated by the deconstruction of amorphous portions and robust cell wall. 23.7 % Xylooligosaccharides (degree of polymerization 2–6), 47.5 % DES‐isolated lignin, and 19.2 % cellulose enzymatic lignin were harvested via this coupled process. This study could promote the precise design of sustainable tandem pretreatment that can boost the frontier of highly available biorefinery. [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]

• Revalorization of vine shoots by a low time consuming and sustainable treatment. • Synergic effect of the temperature and reaction time during the autohydrolysis. • Simulation of microwave-assisted autohydrolysis conditions by conventional heating. • Similar characteristic of the products independently of the heating method. This work deals with the revalorization of an important winery residue such as the vine shoots by the obtaining of oligosaccharides with potential prebiotic activity. The manufacture of these added-value products was performed by an autohydrolysis treatment assisted with microwaves to make the process less time consuming and more environmentally friendly. The influence of the reaction time (0–40 min) and the temperature (140–200) on the production of oligosaccharides during the microwave-assisted autohydrolysis was evaluated. The highest concentration of oligosaccharides (168.3 g/Kg oven-dried vines shoots) was achieved during the treatment carried out at 180 °C for 20 min. To assess the benefits of the assistance of the autohydrolysis treatment with the microwaves a conventionally heated treatment was performed using conditions (180 °C for 15 min) that provoked similar effects on the solubilisation of the hemicellulosic fraction. This treatment permitted the obtaining of 203.5 g oligosaccharides/Kg oven-dried vines shoots using 61.0% more of the time needed to carry out the microwaves-assisted autohydrolysis. Although the microwave-assisted treatment permitted the manufacture of a lower amount of oligosaccharides, only consumed 28.8% of the energy needed to perform the conventionally heated treatment. The oligosaccharides manufactured by the two treatments were substituted xyloglucans with different polymerization and acetylation degrees, which due to their potential prebiotic activity could be highly appreciated by pharmaceuticals and food industries. Thus, this work demonstrated the environmental sustainability of the microwave-assisted autohydrolysis for the revalorisation of the vine shoots. [ABSTRACT FROM AUTHOR]

• Autohydrolysis of post-fibre extraction pulp from banana pseudostem was studied. • A high concentration of malto-oligosaccharides was obtained in the liquors. • Solid fraction presented an improved enzymatic digestibility for further valorization. • Two-stage autohydrolysis improved oligosaccharides production and solid digestibility. Banana's pseudostem pulp (BPP) is a potential by-product obtained in the mechanical fiber extraction of banana's pseudostem. Its chemical characterization revealed to have an interesting composition, with a high polysaccharides content and low content in lignin, which makes it particularly relevant for the biorefinery's biochemical platform. Autohydrolysis pretreatment, studied under isothermal (140 °C) and non-isothermal conditions (140–220 °C), yielded oligosaccharides, mainly gluco -oligosaccharides, as the main soluble products. The highest oligosaccharides production (24 g/100 g raw material) was obtained at a severity factor of 2.3. Autohydrolysis pretreatment effectively disrupted the structure of the material, inducing an improvement of the enzymatic digestibility from 73% for the raw material up to 90% for the most severe conditions. Two stage autohydrolysis, with increasing severity, was also studied, allowing to obtain a higher amount of oligosaccharides (32 g/100 g raw material) and higher digestibility of the remaining solid (up to 97%). [ABSTRACT FROM AUTHOR]

Pressurized hot water pretreatment was performed on softwood (SW) and hardwood (HW) chips following the same conditions (1 h at 170 °C) in order to partly hydrolyse hemicelluloses. The complete characterization of these sugar enriched autohydrolysates (AH) being rather complex, two different purification methods were conducted. Nanofiltration (NF) 1kDa membrane and ultrafiltration (UF) 3 and 5kDa membranes were used to separate oligosaccharides (OS) from undesired compounds and for their molar mass fractionation. Granulated activated charcoal (GAC) adsorption was also used for hydrolysates detoxification. The chemical nature of OS and side charge groups vary significantly depending of the fractions obtained, e. g. xylans' chain length is positively correlated with the degree of acetylation. UF at 5kDa allows for the total separation of galactoglucomannans (GGMs) from xylans, in SW AH, however, this result was not achieved with HW. From the acid soluble lignin (ASL) removal point of view, membrane filtration from 1kDa is more efficient than activated carbon treatment concerning HW AH, on the contrary to SW AH. Regarding the lignin to OS ratio, for both species, GAC leads to a better sugar purity. [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]

Several lignocellulosic wastes are generated in the pulp and paper industry (PPI), such as small wood chips (pinchips) and paper sludge, presenting a high cellulose content suitable to be converted into biofuels or bio-products in a forest biorefinery scheme. In this work, two schemes of biorefinery were proposed for their valorization, processing small eucalyptus wood pinchips in two different strategies: (i) autohydrolysis at 230ºC, and (ii) autohydrolysis at 195ºC followed by organosolv process (47.7% ethanol-water, 198ºC for 60 min). More than 95% of cellulose was recovered in both schemes. In the combined process, 76% of delignification was achieved and 78% of xylan was solubilized as xylooligosaccharides. To reduce operational cost of lignocellulosic biomass-to-ethanol fermentation, the mixture of the treated eucalyptus pinchips from two processes with sludge was also proposed to increase the initial glucan content and to supply a rich source of nitrogen (present in the sludge). For that, two experimental designs were carried out for ethanol production by simultaneous saccharification and fermentation (SSF) process. Ethanol from SSF assays using sludge as co-substrate at 0.6 g of sludge/g of treated wood pinchips and 16 FPU/g of pretreated solids allowed to obtain 59 g/L (90% of conversion) and 46 g/L (96% of conversion) when blended with the wood from autohydrolysis and with the wood from autohydrolysis followed by organosolv, respectively. Overall, this study shows an alternative process valorization of biomasses derived from PPI for production of advanced biofuels and bio-products (such as xylooligosaccharides and lignin) contributing to achieving a circular economy. • Multi-waste valorization approach was proposed to produce biofuel and bioproducts. • Autohydrolysis and organosolv processes allowed > 90% glucan recoveries. • Higher than 40 g/L of ethanol and 90% of yield were obtained in both schemes developed. • Blending with sludge improve ethanol production from pretreated eucalyptus wood. [ABSTRACT FROM AUTHOR]

Autohydrolysis and kraft pulping were sequentially applied to Eucalyptus urograndis wood to obtain added-value products from hydrolysis liquor. A biorefinery approach was used to bleach the resulting solid phase containing the cellulose pulp with an optimized O-D-(EP)-D bleaching sequence, where O denotes delignification with the sequence D bleaching with chlorine dioxide and EP alkaline extraction with soda and hydrogen peroxide. The pulp was then beaten to obtain paper sheets. The two-stage process yielded pulp with a small Kappa number relative to conventional delignification (4.9 to 13.7 vs 17.1). Using autohydrolysis temperatures of 160 °C to 170 °C during 0 min to 15 min made the process selective towards the extraction of hemicelluloses (xylan up to 43.9%). Additionally, the Kappa number and brightness obtained after bleaching with an O-DEP-D sequence were suitable for preparing dissolving grade pulp. The brightness of the pulp obtained was identical with that of the reference pulp (91.0%) and the Kappa number was smaller (0.2 to 0.6). Beating the pulp for 4500 PFI revolutions produced paper sheets with slightly better tensile strength and tear index than those for sheets from the reference pulp (viz., 90.3 N·m·g-1 and 9.9 mN·m²·g-1, respectively, versus 89.8 N·m·g-1 and 9.7 mN·m²·g-1, respectively). [ABSTRACT FROM AUTHOR]

Rice husk, a residue from agro-industrial processing, is one of the most abundant lignocellulosic feedstocks in South Brazil. In the present study, the uncatalysed steam-exploded rice husk slurry was separated into liquid and solid fractions. The liquor was efficiently hydrolysed using an enzymatic complex produced from the Penicillium echinulatum S1M29 strain, followed by lactic acid production using Lactobacillus buchneri NRRL B-30929, which can consume a blend of xylose and glucose. The laboratory-produced enzyme cocktail proved to be a successful strategy for hydrolysis of the liquor, without the release of by-products that occurs during the usual acid hydrolysis technique. The water-insoluble solids were subjected to simultaneous saccharification and fermentation processes using high solid loading combined with distinct doses of commercial enzymes, producing ethanol via Saccharomyces cerevisiae CAT-1. In total, 12.69 g L−1 lactic acid and 19.17 g L−1 ethanol were produced, demonstrating that this abundant low-value renewable feedstock can be explored using a cleaner, greener, and environmentally friendlier production process. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Eucalyptus nitens wood samples were fractionated by green technologies. • Aqueous processing resulted in selective hemicellulose solubilization. • Organosolv delignification enabled an extensive and selective delignification. • The various fractionation products were characterized for composition. • The experimental data define the possible applications of the target fractions. Abstract Following an integrated approach, Eucalyptus nitens wood samples were subjected to consecutive stages of aqueous fractionation and organosolv delignification, in order to separate hemicelluloses (mainly converted into soluble products from the aqueous stage) from lignin (largely converted into soluble fragments in the organosolv stage) and from cellulose (accumulated in the solid phase from pulping). The compositions of selected reaction media were studied by selected spectrophotometric, spectrometric, chromatographic, and nuclear magnetic resonance methods; and the solid phases from treatments were studied by diffractometry and scanning electron microscopy. The experimental information from the above tasks provides a deep insight on the yields, properties and potential applications of the target fractions in the scope of biorefineries. [ABSTRACT FROM AUTHOR]

In this work, we assessed the potential of southern cattail (Typha domingensis) as a lignocellulosic material for producing furfural in some regions. Also, we modeled and optimized the process involving autohydrolysis of the raw material, and its subsequent separation by liquid–liquid extraction and simple distillation. The process is based on biorefining principles and aimed at preserving the integrity of other polymer fractions of the raw material for subsequent use. The autohydrolysis liquor and furfural were characterized by Fourier-transform infrared spectroscopy (FTIR), ultraviolet–visible spectroscopy, and high pressure liquid chromatography (HPLC). Also, a central composite factor design was used to model and optimize the autohydrolysis/liquid–liquid extraction process for conversion of hemicellulosic materials into furfural. Based on the results, southern cattail is a suitable material for extracting hemicellulose to be converted into furfural while preserving other fractions of use for other purposes. The optimum operating ranges for the autohydrolysis conditions were found to be 177–189 °C and 30–45 min. Under such conditions, 20–25% of all xylan in the raw material was converted into furfural with little simultaneous production of degradation products. Furfural in the autohydrolysis liquor was separated virtually quantitatively by extraction with chloroform and subsequent simple distillation. [ABSTRACT FROM AUTHOR]

Highlights • HT produces a cellulose rich solid with high susceptibility to enzymatic attack. • EH efficiency is negatively affected by solid loading increase. • Cellulases undergo rapid activity lose during the first hours of saccharification. • Horizontal bioreactors improve glucose production at high solid loadings. Abstract One of the major challenges in biofuels production from lignocellulosic biomass is the generation of high glucose titers from cellulose in the enzymatic hydrolysis stage of pretreated biomass to guarantee a cost-effective process. Therefore, the enzymatic saccharification on cellulose at high solid loading is an alternative. In this work, the agave bagasse was hydrothermally pretreated and optimized at 194 °C/30 min, obtaining a pretreated solid rich in cellulose content (>46.46%), and subjected to enzymatic hydrolysis at high solid levels. A horizontal bioreactor was designed for enzyme saccharification at high solid loadings [25% (w/v)]. The bioreactor improved mixing efficiency, with cellulose conversions up to 98% (195.6 g/L at 72 h). Moreover, mathematical modeling of cellulase deactivation demonstrated that cellulases lose most of their initial activity in the first hours of the reaction. Also, cellulose was characterized by X-ray diffraction, and the pretreated solids were visualized using scanning electron microscopy. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to optimize hydrothermal treatments (autohydrolysis) for selective hydrolysis of hemicelluloses in the residues obtained from the industrial steam distillation of Cistus ladanifer (rock-rose) for essential oil extraction (CLR). The effect of the autohydrolysis in the removal of extractives of these residues was also evaluated. Methods: The raw material was treated with water in a 6:1 liquid-to-solid ratio (w/w) and the effect of temperature (130–230 °C) on the composition of liquid and solid phases were evaluated and interpreted using the severity factor (log R0). Results: The highest recovery of oligosaccharides (24.7 g/L), corresponding to a yield of 28.4 g/100 g of CLR was obtained at moderate conditions, log R0 of 3.12. Together with hemicelluloses, polar extracts were also largely solubilized during the hydrothermal process yielding hydrolysates with a relevant concentration of phenolics. The highest glucan content (35.6 g/100 g of CLR) of the solid residue was obtained at more severe conditions, log R0 of 4.0 (220 °C). There was no apparent lignin solubilisation in any of the conditions, which is an advantage of this hydrolytic pretreatment. Conclusions: Cistus ladanifer residues demonstrated to have potential to be used in the biorefinery framework with a full upgrade of all biomass fractions. [ABSTRACT FROM AUTHOR]

The biorefinery concept integrates processes and technologies for an efficient biomass conversion using all components of a feedstock. Sargassum muticum is an invasive brown algae which could be regarded as a renewable resource susceptible of individual valorization of the constituent fractions into high added-value compounds. Microwave drying technology can be proposed before conventional ethanol extraction of algal biomass, and supercritical fluid extraction with CO2 was useful to extract fucoxanthin and for the fractionation of crude ethanol extracts. Hydrothermal processing is proposed to fractionate the algal biomass and to solubilize the fucoidan and phlorotannin fractions. Membrane technology was proposed to concentrate these fractions and obtain salt- and arsenic-free saccharidic fractions. Based on these technologies, this study presents a multipurpose process to obtain six different products with potential applications for nutraceutical, cosmetic and pharmaceutical industries.

An integrated strategy was followed to valorise rice straw, one of the most relevant biomass feedstocks available worldwide, to selectively recover solubilised hemicelluloses and lignin. The pathway encompassed the use of autohydrolysis to hydrolyse the hemicelluloses and an ethanol-based organosolv process to solubilise lignin. Several autohydrolysis conditions were assayed with the best results obtained at 210 ºC (log R0 4.15), which enabled high removal of hemicelluloses, yielding an oligosaccharide-rich hydrolysate and a treated biomass with low content of hemicelluloses and enriched in cellulose and lignin. The effects of ethanol concentration (5 to 75%), and reaction time (0 to 24 h) on lignin removal under mild temperature (30 ºC) were studied. In optimal conditions (60.5% ethanol, 24h) the delignification yield reached 42%, whereas glucan solubilisation was below 17%. Lignin solubilisation yield was not influenced by the organosolv treatment duration while ethanol concentration favored the delignification up to 60.5% ethanol. The organosolv liquors contained economic interesting lignin-derived compounds such as vanillin, ferulic, and coumaric acids. The chemical composition and enzymatic digestibility of the treated biomass from autohydrolysis and organosolv delignification were compared, with the latter presenting an almost 10% higher enzymatic digestibility than the former.

This work was focused on evaluating two mixtures of lignocellulosic feedstock, forest and marginal land resources, in order to co-produce solid biofuel, oligosaccharides, and glucose under a biorefinery concept. The selection of renewable bio-mixtures was based on different criteria, namely, territorial distribution, fire risk during summer months and total sugar content. The two mixtures were submitted to autohydrolysis pretreatment under non-isothermal conditions (in the range of 190 °C - 240 °C corresponding to severity of 3.71–4.82). Both mixtures were compared in terms of fractionation (cellulose and lignin recoveries and hemicellulose solubilization), analyzed for thermal properties (high heating values) and for enzymatic susceptibility of cellulose. The highest xylan recoveries (62 and 69%), as xylose and xylooligosaccharides, were achieved for both mixtures in the liquid phase at 206 °C. Autohydrolysis pretreatment increased the high heating values of the two mixtures presenting an alternative use of solid fraction as solid biofuel. Moreover, enzymatic susceptibility of these pretreated mixtures was also improved from 45 to 90% of glucose yield by increasing pretreatment severity. This comparative study of autohydrolysis showed a suitable process for the valorization of both mixtures within a biorefinery concept. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Autohydrolysis and [bmim]Ace were combined for pretreatment of T. austromongolica. • Multi-products of XOS, high-purity lignin, and accessible cellulose were acquired. • Deciphering the varied fate of hemicelluloses and lignin for waste-free biorefinery. • The changes of components, rigid fiber, and cellulose I to II fostered hydrolysis. • Co-yields of 6.1% XOS (DP 2–6), 35.2% glucose and 17.8% lignin from raw material. Abstract Fractional pretreatment of lignocellulose is compelling to synergistically enhance its carbohydrate and lignin outputs for the extension of renewable energy sources. A two-stage approach using hydrothermal and ionic liquid (1-butyl-3-methylimidazoliumacesulfamate, [bmim]Ace) pretreatments was evaluated for hierarchically extracting hemicelluloses and lignin from Tamarix austromongolica , while providing a cellulose-rich fraction that could be readily hydrolyzed by cellulase for the recovery of fermentable glucose and residual lignin. Autohydrolysate-derived xylooligosaccharides (XOS), high-quality lignin, and accessible cellulose were successively acquired at the end of the process. The molecular weights, structural characteristics, functional groups and transitional fate of hemicelluloses and lignin were thoroughly explored towards a waste-free concept. This integrated biorefinery removed the amorphous portions, disrupted the rigid structure and altered cellulose I to II, thereby improving the enzymatic digestibility from 11.6 to 90.2%. Results confirmed that 60.98 mg/g XOS (DP 2–6), 352 mg/g glucose and 178.2 mg/g lignin were harvested via this coupled process. In-depth HSQC and 31P NMR techniques signified that the lignins contained large amounts of β-aryl ether units and hydroxyl groups, rendering them essentially suitable for depolymerizing into aromatic chemicals from biomass to energy. It was reasonable to diversify the energy-oriented product portfolio as a function of this sequential process, such as high-purity XOS, fermentable glucose and lignin, which can remarkably boost the feasibility of bioenergy. [ABSTRACT FROM AUTHOR]

The production of tequila in Mexico generates a large amount of agave bagasse per year. However, this biomass can be considered as a potential source for biofuel production. In this study, it is described how the hydrothermal pretreatment was scaled in a bench scale, considering the severity index as a strategy. The best condition was at 180 °C in isothermal regime for 20 min with 65.87% of cellulose content and high concentration of xylooligosaccharides (15.31 g/L). This condition was scaled up (using severity factor: [log R 0 ] = 4.11), in order to obtain a rich pretreated solid in cellulose to perform the enzymatic hydrolysis, obtaining saccharification yields of 98.5 and 99.5% at high-solids loading (10 and 15%, respectively). The pre-saccharification and fermentation strategy was used in the bioethanol production at 10 and 15% of total pretreated solids, obtaining 38.39 and 55.02 g/L of ethanol concentration, corresponding to 90.84% and 87.56% of ethanol yield, respectively. [ABSTRACT FROM AUTHOR]

Lignocellulosic materials represent a promising low-cost and abundant raw material which does not compete with foodstuffs, but an appropriate pretreatment is required to make sugars easily available. In this work, Eucalyptus grandis wood was subjected to autohydrolysis pretreatment under mild operational conditions (6–10 g/g liquid to solid ratio, 140–160 °C, reaction times up to 150 min) in order to recover and preserve hemicelluloses, while enhancing enzyme accessibility to cellulose. The severity of the pretreatment should be chosen depending on the subsequent use of the separated products. Pretreatment at 160 °C for 150 min using a liquid to solid ratio of 6 g/g was the best condition for hemicellulose recovery (mostly as xylose) in the liquid fraction. Under these autohydrolysis pretreatment conditions, an additional alkaline pretreatment applied to the autohydrolyzed solids was evaluated in order to improve the enzymatic hydrolysis of pretreated wood. Also, the addition of surfactant was assessed in order to enhance the enzymatic hydrolysis. The highest cellulose hydrolysis was obtained in the presence of PEG 6000. For the autohydrolysis-pretreated solids, a cellulose conversion of 39% was obtained, corresponding to an overall glucose yield of 18.7 kg per 100 kg of dry raw material. Additionally, for the autohydrolysis-alkaline-pretreated solids, a cellulose conversion of 43% was achieved, which corresponds to an overall glucose yield of 15.4 kg per 100 kg of dry raw material. [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 efficiency of enzymatic saccharification of lignocellulosic biomass is a key step for biofuels production in the biochemical biorefineries. A novel sequential process, hydrothermal pretreatment followed by enzymatic hydrolysis, of agave bagasse was investigated to improve the release of sugars and the methane production. After optimization of the hydrothermal pretreatment by surface response methodology, a hemicellulose removal of 93.6% was obtained at 180 °C/50 min. Hemicellulose removal enhanced cellulose depolymerization during the enzymatic hydrolysis of the pretreated bagasse by 2.3 times as compared to the untreated bagasse. The single-stage batch methane production of the hydrothermal and enzymatic hydrolysates were 0.223 ± 0.02 NL CH 4 / g COD add and 0.305 ± 0.03 NL CH 4 /g COD add respectively, indicating a higher biodegradability of the enzymatic hydrolysate. The combined energy recovered from the hydrothermal and enzymatic hydrolysates was 3.4 times greater than that recovered from untreated agave bagasse hydrolysate. Also, the combined energy recovery was higher than the energy recovery reported in the literature for agave bagasse pretreated with other chemical and hydrothermal pretreatments. Overall, this study enhanced the saccharification efficiency and biodegradability of polysaccharides present in agave bagasse through efficient saccharification of cellulose and hemicellulose. This was reflected in a high value of combined energy recovery efficiency (54.1%) in the form of methane. [Display omitted] • Hydrothermal pretreatment was optimized by surface response methodology. • The pretreatment enhanced cellulose enzymatic saccharification by 2.3 times. • A maximum hemicellulose removal during hydrothermal pretreatment was 93.6%. • Cellulose enzymatic saccharification yield of pretreated bagasse was 81.8%. • Total energy recovery was higher than for other processes. [ABSTRACT FROM AUTHOR]

Vine shoots, considered a residue from winery operations, possess valuable antioxidant and antimicrobial activities that can be potentially obtained under the scheme of biorefinery. In this framework, we evaluated the autohydrolysis of vine shoots combined with a further stage of extraction with ethyl acetate as viable valorization process. The extraction yield ranged from 0.95 to 3.80 g extract/100 g vine shoots. Moderately high temperature (215 °C) was required for the maximum recovery of phenolics, flavonoids and antioxidant activities. The major phenolic compounds identified were derived from lignin: vanillin, acetovanillone, guaiacylacetone, syringaldehyde and acetosyringone. The ethyl acetate extract from the liquors obtained at 200 °C was assayed for antimicrobial activity against Gram positive and negative bacteria showing values of MIC and MBC in the range of 5–20 mg/mL. This work showed that the antioxidant extracts could be used as cheap source of natural compounds, with potential applications in the food and pharmaceutical industries. [ABSTRACT FROM AUTHOR]

[Display omitted] • Effect of temperature and solid load (SL) on xylooligosaccharides (XOS) yield. • Yield of 96% of XOS was achieved at 190 °C and 2.93% SL. • Yield of 10% of cello-oligosaccharides (COS) was obtained at 190 °C and 17.07% SL. • 5.5 to 13.2% of XOS can be obtained from tobacco stem varying SL. Tobacco stem is an abundant and inexpensive renewable source to produce prebiotics by circular economy. In this study, hydrothermal pretreatments were evaluated on the release of xylooligosaccharides (XOS) and cello-oligosaccharides (COS) from the tobacco stem by a central composite rotational design associated with response surface methodology to evaluate the effects of temperature (161.72 to 218.3 °C) and solid load (SL) (2.93 to 17.07%). XOS were the main compounds released to the liquor. Desirability function was performed to maximize the production of XOS and minimize the effects of release of monosaccharides and degradation compounds. The result indicated yield of 96% w[XOS]/w[xylan] for 190 °C-2.93% SL. The highest value for COS and total oligomers content (COS + XOS) was 6.42 g/L and 17.7 g/L, respectively, for 190 °C-17.07% SL. The mass balance for the best yield XOS condition predicted 132 kg of XOS (X2-X6) from 1000 kg of tobacco stem. [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.

A trihybrid clone of Paulownia fortunei x tormentosa x elongata was used for pulp and paper production using the soda-anthraquinone (AQ) process, comparing the results with those from Paulownia fortunei. An autohydrolysis process had been previously carried out on this raw material. A composite central experimental design and a multiple regression were used for modeling and optimizing the process. A valuable liquid phase could be obtained from the autohydrolysis process of Paulownia, trying to minimize cellulose degradation for pulp and paper production. A compromise to maximize the glucan and minimize the xylan contents in the postautohydrolysis solid phase could be achieved at 187.5ºC and 15 minutes. A suitable cellulosic pulp with kappa number ranging from 12.2 to 69.2 and ISO brightness from 18.2 to 30.6% presented better results than those from other studies. Regarding handsheets physical properties (tensile index 37.3 N•m/g ) and viscosity (848 cm3/g), significant improvements could be obtained when compared with previous results of a similar process using Paulownia fortunei or Paulownia elongata.

The aim of this work was the evaluation of lime pretreatment combined or not with previous step of autohydrolysis for oat straw valorization. Under selected conditions of lime pretreatment, 96% of glucan and 77% of xylan were recovered and 42% of delignification was achieved. Xylose fermentation to ethanol by metabolic engineered Saccharomyces cerevisiae (MEC1133) strain improved the ethanol production by 22% achieving 41 g/L. Alternatively, first step of autohydrolysis (S 0 = 4.22) allowed a high oligosaccharides recovery (68%) and subsequent lime pretreatment attained a 57% of delignification and 99% of glucan to glucose conversion. Oat straw processed by autohydrolysis and lime pretreatment reached the maximal ethanol concentration (50 g/L). Both strategies led to oat straw valorization into bioethanol, oligosaccharides and lignin indicating that these pretreatments are adequate as a first stage within an oat straw biorefinery. [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]

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]

The objective of this work was to study the release, identification and characterization of phenolic compounds by saponification of non-isothermal autohydrolysis liquors of corn (Zea mays) cobs andEucalyptus globulus. Corn cobs andE.globulusare lignocellulosic materials with high contents in cellulose and hemicelluloses. Efficient use of these materials can be achieved using autohydrolysis as the first stage of a biorefinery, resulting in a solid phase rich in cellulose and lignin, and a liquid phase containing essentially hemicelluloses-derived compounds and phenolic compounds from the partial solubilization of lignin. This work studied the combination of alkaline hydrolysis and extraction with organic solvents to maximize the amounts of released phenolic compounds since these compounds are interesting for their properties and food applications. [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 biorefinery concept integrates processes and technologies for an efficient biomass conversion using all components of a feedstock. Sargassum muticum is an invasive brown algae which could be regarded as a renewable resource susceptible of individual valorization of the constituent fractions into high added-value compounds. Microwave drying technology can be proposed before conventional ethanol extraction of algal biomass, and supercritical fluid extraction with CO2 was useful to extract fucoxanthin and for the fractionation of crude ethanol extracts. Hydrothermal processing is proposed to fractionate the algal biomass and to solubilize the fucoidan and phlorotannin fractions. Membrane technology was proposed to concentrate these fractions and obtain salt- and arsenic-free saccharidic fractions. Based on these technologies, this study presents a multipurpose process to obtain six different products with potential applications for nutraceutical, cosmetic and pharmaceutical industries. [ABSTRACT FROM AUTHOR]

An integrated strategy was followed to valorise rice straw, one of the most relevant biomass feedstocks available worldwide, to selectively recover solubilised hemicelluloses and lignin. The pathway encompassed the use of autohydrolysis to hydrolyse the hemicelluloses and an ethanol-based organosolv process to solubilise lignin. Several autohydrolysis conditions were assayed with the best results obtained at 210 °C (log R0 4.15), which enabled high removal of hemicelluloses, yielding an oligosaccharide-rich hydrolysate and a treated biomass with low content of hemicelluloses and enriched in cellulose and lignin. The effects of ethanol concentration (5 to 75%), and reaction time (0 to 24 h) on lignin removal under mild temperature (30 °C) were studied. In optimal conditions (60.5% ethanol, 24h) the delignification yield reached 42%, whereas glucan solubilisation was below 17%. Lignin solubilisation yield was not influenced by the organosolv treatment duration while ethanol concentration favored the delignification up to 60.5% ethanol. The organosolv liquors contained economic interesting ligninderived compounds such as vanillin, ferulic, and coumaric acids. The chemical composition and enzymatic digestibility of the treated biomass from autohydrolysis and organosolv delignification were compared, with the latter presenting an almost 10% higher enzymatic digestibility than the former. [ABSTRACT FROM AUTHOR]

The chemical composition of black liquors obtained from the soda-AQ pulping of birch ( Betula pendula) sawdust was studied as a function of cooking time, effective alkali content, and hot-water pretreatment of the sawdust prior to delignification. Special attention was paid on the formation of lignin-derived materials and low-molecular-mass carbohydrate-derived degradation products containing aliphatic carboxylic acids. In the case of the hot-water-pretreated feedstock, less acetic acid and formic acid and more nonvolatile hydroxy acids (especially monocarboxylic acids) were obtained. The observations can be interpreted as a result of the extensive removal of hemicelluloses during the hot-water pretreatment. [ABSTRACT FROM AUTHOR]

In this study, the fractionation of sugarcane bagasse at low liquor-solid ratio (LSR) was firstly reported. The effect of low LSR fractionation of sugarcane bagasse by hot water autohydrolysis and organosolv delignification that consume minimal amounts of water was studied to obtain a cellulosic fraction (glucans) that is suitable for conversion to ethanol. Hot water pretreated bagasse was delignified using varied process conditions: 160–190 °C, 30–150 min and LSR 3–9. The results were compared with the untreated bagasse using the same delignification conditions. The delignification of the pretreated bagasse extracted of 86.7% of lignin and produced a solid with 90.0% of glucans (190 °C for 150 min and LSR 9). A solid consisting of 82.9% of glucans with a slightly greater lignin content was obtained with a LSR 3 whilst delignification of untreated bagasse extracted 91.3 and 92.0% of lignin (87.7 and 88.4% of glucans) for LSRs 3 and 9, respectively. Low liquor–solid ratio fractionation allowed the direct separation of the hemicelluloses and lignin to produce a solid with high glucans. [ABSTRACT FROM AUTHOR]

Microwave hydrothermal treatment (MHT) is considered a sustainable technology for the valorization of lignocellulosic materials, enabling the solubilization of hemicellulosic-derived compounds, especially in the form of oligosaccharides that may present potential in the chemical, pharmaceutical or nutraceutical industries. Hence, MHT at 200 and 230 °C, at severity (S 0) among 2.92–4.66 were performed. S 0 = 3.98 permitted the recovery of about 80% of the initial xylan as xylooligosaccharides. In order to compare the effectiveness of MHT, conventional hydrothermal treatment (CHT) was performed at conditions leading to the maximum recovery of oligosaccharides (S 0 =3.98, non-isothermal regime at 203 °C). Despite the structural features of oligomers in the three liquors were very similar, the spent solids presented different enzymatic digestibility, which implied a different effect of the treatments, reaching up to 80% of glucan to glucose conversion for the solid after MHT at 230 °C for 0.5 min. Additionally, CHT consumed 2.1–2.8-fold greater energy than MHT, reflecting that microwave-assisted autohydrolysis is a sustainable and efficient technology to process PW. [Display omitted] • Microwave (MHT) and conventional (CHT) hydrothermal treatments were evaluated. • Up to 80% xylan conversion into xylooligosaccharides via hydrothermal treatments. • Polyphenolic profile of Paulownia extracts was identified via HPLC-ESI-MS. • Glucose conversions of 64–80% after saccharification of MHT and CHT solids. • Up to 64.7% energy is saved using MHT comparing to CHT. [ABSTRACT FROM AUTHOR]