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An innovative approach for preparing hemp fibers from hemp hurds for use in tissue and towel grades of paper is described. Hemp hurds are a low value by-product of industrial hemp processing that are generally used for animal bed litter. Tissue paper was fabricated from hemp hurd fibers by following three pulping processes: autohydrolysis (hydrothermal), sodium carbonate-based defibration, and high yield kraft pulping, and benchmarked against hardwood pulp. To meet industrial standards, hardwood and hemp pulp fibers were mixed at a dry mass ratio of 75:25, from which tissue paper sheets were prepared. Desirable tissue paper properties, such as water absorption, burst resistance, softness, and tensile strength (dry and wet), were measured and compared. Characterization of morphological and chemical properties of tissue handsheets was conducted with SEM and time-of-flight-secondary ion mass spectrometry (ToF-SIMS). The combined kraft pulped hardwood and autohydrolyzed hemp pulp fibers displayed improvements in tensile index, burst resistance, and softness of tissue handsheets compared to only kraft hardwood pulp handsheets without adversely impacting water absorption. Hardwood fibers showed a sparse distribution of surface lignin compared to hemp fibers using the same defibration. This technology can lead to a variety of eco-friendly tissue paper products that are not only highly energy efficient, but avoid harsh chemical processing. [ABSTRACT FROM AUTHOR]

An autohydrolysis pretreatment with different conditions was applied to sugarcane bagasse to compare the impacts of the physicochemical properties and hydrolytic inhibitors on its enzymatic hydrolysis. The results indicate that the autohydrolysis conditions significantly affected the physicochemical properties and inhibitors, which further affected the enzymatic hydrolysis. The inhibitor amount, pore size, and crystallinity degree increased with increasing autohydrolysis severity. Furthermore, the enzymatic hydrolysis was enhanced with increasing severity owing to the removal of hemicellulose and lignin. The physicochemical obstruction impeded the enzymatic hydrolysis more than the inhibitors. The multivariate correlated component regression analysis enabled an evaluation of the correlations between the physicochemical properties (and inhibitors) and enzymatic hydrolysis for the first time. According to the results, an autohydrolysis with a severity of 4.01 is an ideal pretreatment for sugarcane bagasse for sugar production. [ABSTRACT FROM AUTHOR]

BACKGROUND: Lignocellulosic biomass is a promising renewable feedstock to obtain fuels and chemicals. However, a suitable pretreatment is required to separate its main components and overcome its structural resistance to enzymatic hydrolysis. In this work, a sequential pretreatment composed of autohydrolysis (AH) and organosolv delignification (ORG) is used to fractionate Pinus radiata wood and improve the enzymatic hydrolysis. RESULTS: The effect of three different AH pretreatment severities on the delignification degree of organosolv solid fractions was evaluated. In addition, enzymatic hydrolysis was performed to determine the efficiency of the combination of pretreatments. The results showed that a pretreated solid with high cellulose content (88%, w/w) and high delignification degree (88%) was achieved under mild conditions of AH (150 °C and 30 min) and acid‐catalyzed ORG (185 °C, 75 min, 50% (w/w) ethanol and 1% (w/w) sulfuric acid), obtaining an enzymatic hydrolysis yield of 63%. CONCLUSION: This study provides the most favorable conditions to fractionate a softwood, P. radiata, employing a two‐step pretreatment based on AH followed by ORG. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

• Six brewer's spent grains (BSG) were characterized and compared for ethanol production. • Autohydrolysis at high solid loadings was carried out for BSG fractionation. • Autohydrolysis facilitated enzymatic hydrolysis of BSG using 25% of solid loading. • High concentration of glucooligosaccharides (51.6 g L−1) was obtained from BSG autohydrolysis. • High-gravity ethanol was produced from BSG whole slurry at high solid loadings. This work targets the valorization of brewer's spent grain (BSG) waste by ethanol production, providing strategies for increasing titers in the multiple process steps involved. High solid loadings and use of whole slurry from the pretreatment were evaluated, aiming to achieve high ethanol concentration and yield. As variability in BSG chemical composition presents a challenge for their valorization, six different BSGs were chemically characterized, which allowed the selection of two with high polysaccharide content. High solid loadings (up to 25%) were employed for the pretreatment of selected BSGs by autohydrolysis, an environmentally friendly process, to improve enzymatic saccharification and extract fermentable sugars as oligosaccharides and monosaccharides. As a result, high glucose concentrations (43.7 and 57.7 g L−1) and glucose yield (85.9 and 70.6%) were obtained from the saccharification of the pretreated BSG whole slurry at 20 and 25% solid loading, respectively. Whole slurries from autohydrolysis were used as substrate for ethanol production by hybrid saccharification and fermentation. Two different Saccharomyces cerevisiae strains were evaluated and high ethanol concentration (42.27 g L−1) at a high yield (94.0%) was achieved. The results attained by the combined intensification approaches qualify BSG waste as a valuable renewable resource for cost-effective ethanol production. [ABSTRACT FROM AUTHOR]

Featured Application: Laminaria-psyllium gels with distinct texture and rheological features, designed for a wide range of food applications. Seaweeds are a novel source of important nutritional compounds with interesting biological activities that could be processed into added-value products. In this study, two previously developed products obtained by Laminaria ochroleuca processing (liquid extract and a purée-like mixture) were processed with Psyllium gel to develop functional hydrogels. The optimization of the formulation and the characterization of the Laminaria-Psyllium gels in terms of their mechanical features have allowed the proposal of potential food applications. A beneficial interaction was found between Laminaria and Psyllium in terms of the reinforcement of texture and rheological properties. The obtained outcomes could provide new healthy gelling formulations with attractive properties to alleviate the growing market demand of eco-novel food matrices. [ABSTRACT FROM AUTHOR]

Sargassum muticum , an invasive macroalgae in Europe, was employed as material for third generation bioethanol production. As a first step, autohydrolysis was chosen as an eco-friendly pretreatment, seeking for a high enzymatic susceptibility of the solid phase and high content of hexoses as glucose, galactose and mannose, in both liquid and solid phases, which can be subsequently transformed in ethanol via fermentation. Besides, the search of a minimum consumption of energy in the pretreatment is also a key challenge in bioethanol production. At optimum conditions of autohydrolysis pretreatment, more than 90% of the glucan was recovered in the solid phase (while the other 10% appeared as glucooligosaccharides and glucose in the liquid phase). In the enzymatic hydrolysis carried out with the solid phases, glucan to glucose conversions of 94 and 89% were obtained, with the solid mixed with water and the whole slurry, respectively. Moreover, the whole slurry experiments, where all hexoses present in the raw material (glucose, galactose and mannose) from the solid and the liquid phases are fermented, allows to reach maximum ethanol yields of 80% (14.10 g of ethanol/L) referred to the theoretical yield, in a short time. • Autohydrolysis is a suitable pretreatment for bioethanol production from Sargassum. • Almost 100% of hexoses are recovered in the optimum conditions. • Glucan to glucose conversion above 90% was achieved in enzymatic hydrolysis assays. • SSF without nutrients reached 80–95% theoretical ethanol yield in less than 10 h. [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]

Lignin is a biopolymer usable in many ways once it has been separated and delignified from biomass. In this training report, delignification of coconut husk fibres is performed, with the aim of recovering isolated lignin. In order to do so, different processes are carried out (autohydrolysis, dilute acid, organosolv and soda pulping treatments). The obtained lignin is characterised afterwards through Fourier transform infrared (FTIR), 1H and 13C nuclear magnetic resonance (NMR) in order to check lignin presence and quality. Analyses show that lignin is indeed obtained in both experiments, though the yield is greater for the treatment with autohydrolysis. However, the global yield is quite low, adjustments of experimental parameters (time, temperature, ratio) shall be carried out. [ABSTRACT FROM AUTHOR]

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

Enzymatic hydrolysis accounts for 20% of the total cost in the conversion process of lignocellulosic biomass into bioethanol. Therefore, production of biomass-degrading enzymes by using lignocellulosic residue as a fermentation substrate may be an alternative to decrease the production costs. In this study, corncob (CC) has been pretreated by liquid hot water (LHW) at 200 °C for 30 min and used as inducer source for production of biomass-degrading enzymes by Trichoderma reesei MUM 97.53. The pretreatment was used to increase the cellulose content and the accessibility to lignocellulosic material. Although the filamentous fungus secreted a broad range of cellulolytic and hemicellulolytic enzymes when grown on untreated CC, higher enzyme productions were obtained when cultured on LHW-pretreated CC in a 2-L stirred tank bioreactor (STB). Besides, the effects of aeration (2 and 4 vvm) and agitation (150 and 250 rpm) rates on enzyme production were studied by submerged fermentation in a batch STB and correlated with the volumetric oxygen transfer coefficient (kLa). Maximal cellulase, xylanase, and β-xylosidase productions were found at 150 rpm and 4 vvm, while the highest β-glucosidase levels were obtained at 150 rpm and 2 vvm, that corresponded to kLa values of 32.50 h−1 and 16.41 h−1, respectively. At higher agitation, a lower enzymatic production was observed probably due to the high shear stress in the fungal hyphae. [ABSTRACT FROM AUTHOR]

Abstract The nut industries generate a high amount of by-products that can be valorized as feedstocks for new processes using green technologies. Hazelnut shells have potential as source of antioxidant compounds with commercial interest in cosmetic, pharmaceutical and food industries. Antioxidants from hazelnut shells can be solubilized in autohydrolysis processes and recovered using resins. The autohydrolysis study led to achieve the highest solid solubilization of 26.7 g of non-volatile compounds (NVC)/100 g of hazelnut shells at 220 °C. Higher temperatures improved the release of phenolic compounds in the aqueous phase up to 3.37 g of gallic acid equivalents (GAE)/100 g of hazelnut shells. The DPPH free radical scavenging capacity allowed to determine the potential activity of the extracted phenolic compounds, and increasing temperatures improved the antioxidant capacity of extracts up to 1.64 g GAE/100 g of NVC in the range 210–230 °C. The phenolic compounds in aqueous phase after autohydrolysis were recovered by adsorption, and the sorption kinetics and the equilibrium isotherms were evaluated. The maximum sorption capacities of assayed resins were 8.9 and 7.7 mg GAE/g resin for Amberlite XAD4 and XAD16HP, respectively. The knowledge provided for this study should be helpful to further exploit and apply phenolic compounds from hazelnut shells as source of natural antioxidant compounds. Highlights • Green processes for antioxidants recovery: Autohydrolysis followed by adsorption. • EC 50 close to 0.16 GAE/L was reached at 210 °C autohydrolysis treatment. • Phenolic yields were significantly improved by increasing temperatures. • The highest adsorption efficiency was provided by SP700 and XAD16HP resins. • Experimental kinetic data fitted with a pseudo-second order model. [ABSTRACT FROM AUTHOR]

• Multi-step pretreatment of pine using autohydrolysis and ionic liquid is proposed. • The autohydrolysis step hamper the subsequent ionic liquid pretreatment of pine. • Fractal dimension and laccunarity are related to enzymatic saccharification. • Surface composition is different to lobal composition of pretreated biomass. • The highest glucose yields is obtained with the sample AH150IL120. Sequential pretreatments provide advantages of every single process towards a complete biomass fractionation. In this work, autohydrolysis and IL microwave pretreatments are sequentialy studied, and their effect to enhance enzymatic hydrolysis is analyzed. Mild, intermediate and severe autohydrolysis are combined with four IL temperatures (50, 80, 120 and 150 °C). Pretreated solids are enzymatically hydrolyzed and compared in terms of chemical composition and morphology. Digital image analysis is employed to numerically determine the heterogeneity of the solids using surface fractal dimension and lacunarity parameters. In this study, the negative effect of intermediate and severe autohydrolysis, over the subsequent IL pretreatment is demonstrated. Mild autohydrolysis and high IL conditions (AH150IL120) results in digestibilities of 78.8 g of glucan/100 g of glucan introduced. High surface fractal values (in the range of 2.5461–2.7124) and low lacunarities (0.0818–0.2563) enhance the enzymatic accessibility of pine wood. Furthermore, the negative effect of softwood lignin accumulation in the surface is observed using confocal fluorescence microscopy. [ABSTRACT FROM AUTHOR]

• Xylan depolymerisation in a pretreatment continuous tubular reactor was analysed. • Autohydrolysis reactions described the xylan depolymerisation dynamics in the reactor. • Wheat straw, corn stover and sugar cane bagasse were used for experimental validation. • Wheat straw showed the highest production of oligosaccharides without degradation. This work proposes a mathematical model for describing the dynamics of xylan depolymerisation of lignocellulosic biomass in a pilot-scale pretreatment continuous tubular reactor. Xylan depolymerisation, modelled as pseudo-homogeneous first order reactions and mass flow dynamics, are described as a set of ordinary differential equations. The model accurately describes the dynamics of xylooligosaccharides and other depolymerisation products at the reactor output. Experimental validations of residence time distribution, mass flow rates and kinetics were carried out at 18 and 37 min of mean residence time for wheat straw, corn stover and sugar cane bagasse. Wheat straw exhibited the highest production of xylooligosaccharides (approximately 70%) without degradation at 37 min of residence time. [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]

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Even though lignin carbon fiber has been sought after for several decades, the poor mechanical performance remains to be a major barrier for commercial applications. The low mechanical performance is attributed to the heterogeneity of lignin polymer. Recent advances in fractionation technologies showed the great potential to reduce lignin heterogeneity, but current fractionation methods often depend on costly chemicals and materials such as enzymes, organic solvents, membranes, and dialysis tubes. Here, a new non‐solvent strategy was developed to fractionate lignin by autohydrolysis. By using only water, lignin was efficiently fractionated into water‐soluble and ‐insoluble fractions. The latter fraction had increased molecular weight and uniformity and resulted in more β‐O‐4 interunitary linkages as analyzed by size‐exclusion chromatography and 2D heteronuclear single quantum coherence NMR spectroscopy, respectively. In particular, the water‐insoluble fraction significantly enhanced the mechanical performances of the resultant carbon fibers. Mechanistic study by differential scanning calorimetry (DSC) revealed that the miscibility of lignin with guest polyacrylonitrile molecules was improved with the reduced lignin heterogeneity. Crystallite analyses by XRD and Raman spectroscopy revealed that the crystallite size and content of the pre‐graphitic turbostratic carbon structure were increased. The fundamental understanding revealed how lignin fractionation could modify lignin chemical features to enhance the mechanical performance of resultant carbon fibers. The autohydrolysis fractionation thus represents a green, economic, and efficient methodology to process lignin waste and boost lignin carbon fiber quality, which could open new horizons for lignin valorization. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Poplar sapwood chips were autohydrolyzed followed by an alkali impregnation. • Other chemical components had less impact on alkali impregnation than surface lignin. • Surface lignin had no effect on alkali impregnation compared to the volume porosity. • Autohydrolysis can facilitate chemi-mechanical pulping. Abstract Chemi-mechanical pulping, a typical high-yield pulping method, combined with autohydrolysis pretreatment prior to pulping is an efficient and value-added utilization method for biomass in pulp and paper industry. This study investigated the surface lignin changes of poplar sapwood chips in autohydrolysis pretreatment and their effect on the subsequent alkali impregnation for chemi-mechanical pulping. The results showed that the surface lignin content went up with the increase of autohydrolysis intensity, and that the existence of the surface lignin had nearly no impact on the subsequent alkali impregnation in making chemi-mechanical pulps (CMPs) compared to the volume porosity, which was validated by using the stepwise regression analysis. It can be further concluded that autohydrolysis can facilitate the subsequent alkali impregnation of the autohydrolyzed sapwood chips in making CMP, which would be of significance for the combination of biomass refinery and pulp and paper industry. [ABSTRACT FROM AUTHOR]

Sargassum muticum was processed by hydrothermal extraction under previously optimized non-isothermal conditions (up to 187 °C). The alginate free crude hydrolysate was further concentrated by ultrafiltration, operating in diafiltration mode to produce an extract (SmE) enriched in the fucoidan and the phlorotannin fractions and with low mineral content and antiradical capacity equivalent to that of Trolox. In order to explore the potential of this concentrated product for food or feed additive, the in vivo antioxidant potential was assessed. Male Sprague–Dawley rats were fed SmE dissolved in distilled water at doses of 0.5, 1.0 or 2.0 g kg−1, administered via an intragastric tube daily for three weeks. The weight and organ gain was not significantly affected in the different groups in relation to the control group fed a standard diet. Serum glucose was significantly lowered in the groups receiving the higher SmE doses, liver GPx levels were reduced and liver TBARS levels decreased in rats administered the extract, but no effect on SOD activity in either liver or erythrocytes was observed. [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]

Eucalyptus sawdust is a residue from the pulp and timber industries which can be used as a raw material in a biorefinery. In this work, two consecutive treatment steps were applied to eucalyptus sawdust from a pulp mill, as a fractionation strategy, to recover and preserve lignocellulosic components while enhancing enzyme accessibility to cellulose. The first treatment step assayed was autohydrolysis (170 °C, 40 min). It was followed by (a) mechanical refining (3000 rpm, 0.5 mm), (b) kraft pulping (155 °C, 90–140 min, alkali charge 2.1–3.4%), or (c) soda pulping (155 °C, 90 min, alkali charge 2.4–4.0% NaOH). The remaining solid fractions were enzymatically hydrolyzed using 25 FPU/g of Cellic CTec 2 from Novozymes and a solid content of 13%. The efficiency of the enzymatic hydrolysis was higher than 70% in the case of an additional kraft or soda pulping while only autohydrolysis led to efficiencies lower than 60%. The best hydrolysis parameters and lignin and xylose recovery yields were obtained for autohydrolysis followed for a kraft pulping (cellulose conversion up to 71%, cellulose hydrolysis 95% at 48 h, lignin and xylose recovery 99 and 85%, respectively). The treated solid that reached the highest enzymatic yields was fermented using Saccharomyces cerevisiae in a 3.5-L reactor. The highest bioethanol yield was found for the autohydrolysis-treated solids followed by soda pulping, reaching a value of 250 L of ethanol per tonne of sawdust. Under this condition of combined treatments, 300 kg lignin/t sawdust and 120 kg xylose/t sawdust can be obtained. [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]

Summary: The temperature effect during autohydrolysis of natural and blanched broccoli was studied. For this purpose, the extraction yield, total phenolic content, antioxidant capacity and glucosinolates type and content of the autohydrolysis liquors have been determined. The development of alginate based hydrogels using the autohydrolysis liquid phase as solvent and the corresponding textural characterisation was also evaluated. In all cases, extraction yields rose with the autohydrolysis temperature up to 150 °C and then decreased. For liquors from natural samples, total phenolic content and antioxidant capacity increased with increasing operation temperature. The opposite trend was identified for blanched samples. Comparable values were obtained at 150 °C for liquors from natural samples and those blanched treated at 100 °C. Glucosinolates content decreased with increasing temperature. Glucoiberin, glucoraphanin, gluconapin, glucobrassicin and gluconasturniin were detected. Hydrogels with suitable textural properties were formulated with the extracted liquors at 100 and 150 °C, independently of the blanching treatment. [ABSTRACT FROM AUTHOR]

Highlights • L. ochroleuca autohydrolysis was optimised for the bioactive compounds production. • At 180 °C, an extract with 17% fucoidan & 12.20% protein was obtained. • Antioxidant capacity 18 mg Trolox/g & 1.25% phlorotannins was found at 180 °C. • Sulfated fucoidan & alginate with suitable viscoelasticity were obtained at 160 °C. • Cell inhibition reached values ≈40% for the extract with higher fucoidan content. Abstract The non-isothermal autohydrolysis temperature impact of edible brown seaweed Laminaria ochroleuca was studied to recover high valuable compounds. Extraction yield was determined, above 80% was obtained at 220 °C. The maximal fucose content (17% d.b.) was attained at 180 °C, whereas the maximal sulphate was achieved at 160 °C, and phenolic and protein content at 220 °C. The maximum sulphated fucoidan content (41.38 g fucoidan/100 g extract) was obtained at 160 °C, whereas the maximum fucose oligosaccharides was obtained at 180 °C. The antioxidant capacity was equivalent to 32 mg Trolox/g dry extract produced at 220 °C. The milder processing condition was selected to study the potentiality of the precipitated alginate in terms of viscoelastic properties determined by rheology. Alginate extraction (14.94 g/100 g extract) was determined at 160 °C. The crude fucoidan fractions were tested at 25–500 μg/mL, showed up to 50% cell growth inhibition in four selected tumoral cell lines. [ABSTRACT FROM AUTHOR]

Abstract The extraction of bioactives from Pleurotus eryngii was addressed using innovative extraction techniques. Microwave hydrodiffusion and gravity, which yielded less than 1% of the initial material, can be proposed as an initial stage to dehydrate the mushroom. Autohydrolysis or hydrothermal extraction using water under subcritical conditions allowed solubilization of up to 80% of the dry weight of the mushroom and produced an extract rich in monosaccharides and oligosaccharides, which also contained 2 g gallic acid equivalents (GAE)/100 g extract and showed antiradical capacity equivalent to 30 mg Trolox/g extract. Supercritical carbon dioxide is an alternative solvent with ability to selectively extract lipophilic fractions (<1% of the initial material) with antioxidant activity. Highlights • Pleurotus enyrgii was extracted with emerging technologies. • Microwave hydrodiffusion and gravity can be proposed as an initial drying stage. • Autohydrolysis solubilizes up to 80% of the dry weight of the mushroom. • Supercritical CO 2 selectively extracts a lipophilic fraction. [ABSTRACT FROM AUTHOR]

Highlights • Vine shoots were tested for prebiotic oligosaccharides (OS) production. • Membrane processing allowed to remove a high percentage of impurities. • Purified OS were characterized by HPLC, FTIR, HPAEC-PAD, MALDI-TOF and UPLC-ESI-MS. • Purified OS were assayed for prebiotic activity showing bifidogenic effect. Abstract Vine shoots were subjected to a hydrothermal treatment to cause the selective solubilisation of the hemicelluloses. The hemicelluloses solubilisation products were refined by a sequential processing with nanofiltration and ion exchange obtaining a refined product with a purity of 99%. A depth chemical and structural characterization of the purified oligosaccharide mixture from vine shoots was performed for the first time by HPLC, FTIR, HPAEC-PAD, MALDI-TOF and UPLC-DAD-ESI-MS. The characterization showed the presence of oligosaccharide mixtures with a wide polymerization degree (DP = 2–17) and a rich substitution pattern. Moreover, the thermal behaviour of the mixture was evaluated by TGA in order to obtain information about the thermal and storage conditions during its incorporation into processed functional foods. The thermal and acid stability of the obtained oligosaccharides was also evaluated corroborating their resistance to the digestive conditions. The assessment of the prebiotic activity of the digested mixture was carried out by in vitro fermentability with faecal inocula from human volunteers by the monitoring of short chain fatty acids production and the population dynamic of bifidobacteria by FISH. [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]

Commercial humic substances (HS) are usually extracted from non-renewable resources such as lignite and coal. In this study, artificial HS (mainly humic-like acid (HLA) and fulvic-like acid (FLA)) was produced from renewable biomass-alkaline xylooligosaccharides manufacturing waste residue (XOR) of corncob via hydrothermal pretreatment (HP), as well as fermentable sugars were coproduced. The HLA yield was highest at 1.5% and the content of FLA was 9.6 g/L after HP at 210 °C for 8 h. The glucose yield of HP-pretreated XOR reached 98.8% at CTec 2 dosages of 20 FPU/g glucan. Structural characterization analysis proved that the structures and compositions of HLA were similar to those of commercial humic acid. The results of mass balance indicated that 100 g of XOR yielded 1.5 g of HLA, 9.6 g of FLA, and 60.4 g of monosaccharides (46.9 g of glucose and 13.5 g of xylose). Therefore, this work provides a promising strategy for valorization of lignocellulosic biomass in producing HLA, FLA, and fermentable sugars. [Display omitted] • Integrated utilizing xylooligosaccharides manufacturing waste residues (XOR). • Residual alkali in XOR was benefit for alkaline hydrothermal pretreatment. • Coproducing humic and fulvic like acids, and fermentable sugars from XOR. • Optimizing the reaction conditions for maximum humic-like acid yield. • The hydrothermal pretreated XOR has an excellent enzymatic hydrolysis yield. [ABSTRACT FROM AUTHOR]

Instant controlled pressure drop (DIC) technology was utilized in the production of glucose from sago pith waste (SPW). In situ autohydrolysis was conducted in a DIC reactor to obtain the maximum glucose production. The influence of pressure, acid concentration, and treatment time on the glucose yield from SPW subjected to DIC-assisted in situ autohydrolysis was determined, and the experimental conditions were optimized using the response surface method. The results showed that the linear term of acid concentration and the quadratic terms of pressure and time had a significant effect on the glucose yield. The optimized experimental conditions for maximum glucose production (48.21%) from SPW subjected to DIC-assisted autohydrolysis were a pressure of 0.1 MPa, acid concentration of 0.1 M, and time of 4 min. The findings demonstrated that DIC technology has the potential to be utilized for the commercial production of glucose from SPW.

There is increasing demand for the production of biofuels from lignocellulosic biomass. Lignocellulosic biomass consists mainly of three polymeric components: cellulose, hemicelluloses, and lignin. The separation of these components requires an effective pretreatment process to ensure high quality glucose production, and is highly influenced by several factors, including moisture content, cellulose crystallinity, lignin content, and available surface area. Over time, numerous pretreatment methods have been utilized to change the lignocellulosic fiber structure and to enhance the enzymatic saccharification of cellulose to polysaccharides. This article reviews thermal-based pretreatment of lignocellulosic fiber used for glucose production. Based on the reviewed studies, autohydrolysis of lignocellusic biomass, followed by the “Instant pressure drop (DIC),” method can be regarded as an effective pretreatment process of lignocellusic biomass.

Untreated and hot-water-extracted (HWE) Norway spruce (Picea abies) sawdust was cooked using the sulfur-free oxygen-alkali (OA) method under the following conditions: temperature, 170 °C; liquor-to-wood ratio, 5:1 L/kg; and NaOH charge, 19% on the oven-dry sawdust. In comparison with earlier studies conducted with birch sawdust, the spruce cooking yield data, together with the amount of the pulp rejects (78% to 86% for reference pulps from the initial feedstock and 73% to 83% for pulps from the HWE feedstock), revealed that the pretreatment stage prior to spruce OA pulping caused different effects on pulping performance. The analyses of the three main compound groups (i.e., lignin, volatile acids, and hydroxy acids) in black liquor indicated that slightly higher contents (25.5 to 45.9 g/L) of dissolved lignin were detected in black liquors originating from the HWE sawdust than in the black liquors from the reference material (27.2 to 39.6 g/L). In contrast, considerably lower (~20% decrease) volatile acid contents and similar or slightly decreased hydroxy acids contents were detected in the black liquors from the HWE sawdust.

Aspen wood was subjected to autohydrolysis as a pre-treatment to characterize the structural changes occurring in lignin fractions during the pre-treatment process. Milled wood lignin (MWL) was isolated from both the native aspen wood and hydrolyzed wood chips, and its structural features were characterized by Fourier transform infrared (FT-IR), quantitative 13C, two-dimensional heteronuclear single quantum coherence (2D HSQC), and 31P nuclear magnetic resonance (NMR) spectroscopies, gel permeation chromatography/multi-angle laser light scattering (GPC-MALLS), and thermal analysis. The lignin remaining in the hydrolyzed wood chips revealed more phenolic OH groups, fewer aliphatic OH groups, higher syringyl/guaiacyl ratios (S/G), higher molecular weights, and narrower polydispersities than the native lignin of aspen wood. The inter-unit linkages of β-O-4 were noticeable cleaved, but the condensed structures in the lignin formed when undergoing autohydrolysis of high severity, resulting in elevated amounts of C-C linkages. Moreover, it was found that autohydrolysis promoted the removal of -OCH3 groups and increased the thermal stability of lignin fractions.

Olive table industry, olive mills and olive pomace oil extraction industries annually generate huge amounts of olive stones. One of their potential applications is the production of bioethanol by fractionation of their lignocellulose constituents and subsequent fermentation of the released sugars using yeasts. In this work, we studied the influence of temperature (175–225 °C) and residence time (0–5 min) in the liquid hot-water pre-treatment of olive stones as well as the initial enzyme loading (different mixtures of cellulases, hemicellulases and β–glucosidases) in the later enzymatic hydrolysis on the release of fermentable sugars. The Chrastil’s model was applied to the d-glucose data to relate the severity of pre-treatment to enzyme diffusion through the pre-treated cellulose. Finally, the hydrolysate obtained under the most suitable conditions (225 °C and 0 min for pre-treatment; 24 CE initial enzyme concentration) was fermented into ethanol using the yeast Pachysolen tannophilus ATCC 32691. Considering the overall process, 6.4 dm3 ethanol per 100 kg olive stones were produced.

Corn stover is the most produced byproduct from maize worldwide. Since it is generated as a residue from maize harvesting, it is an inexpensive and interesting crop residue to be used as a feedstock. An ecologically friendly pretreatment such as autohydrolysis was selected for the manufacture of second-generation bioethanol from corn stover via whole-slurry fermentation at high-solid loadings. Temperatures from 200 to 240 °C were set for the autohydrolysis process, and the solid and liquid phases were analyzed. Additionally, the enzymatic susceptibility of the solid phases was assessed to test the suitability of the pretreatment. Afterward, the production of bioethanol from autohydrolyzed corn stover was carried out, mixing the solid with different percentages of the autohydrolysis liquor (25%, 50%, 75%, and 100%) and water (0% of liquor), from a total whole slurry fermentation (saving energy and water in the liquid–solid separation and subsequent washing of the solid phase) to employing water as only liquid medium. In spite of the challenging scenario of using the liquor fraction as liquid phase in the fermentation, values between 32.2 and 41.9 g ethanol/L and ethanol conversions up to 80% were achieved. This work exhibits the feasibility of corn stover for the production of bioethanol via a whole-slurry fermentation process.

Xylooligosaccharides (XOS) production from sweet sorghum bagasse (SSB) has been barely studied using other edible biomasses. Therefore, we evaluated the XOS content as well as its purity by comparing the content of total sugars from SSB. An environmentally friendly approach involving autohydrolysis was employed, and the reaction temperature and time had variations in order to search for the conditions that would yield high-purity XOS. After autohydrolysis, the remaining solid residues, the glucan-rich fraction, were used as substrates to be enzymatically hydrolyzed for glucose conversion. The highest XOS was observed for total sugars (68.7%) at 190 °C for 5 min among the autohydrolysis conditions. However, we also suggested two alternative conditions, 180 °C for 20 min and 190 °C for 15 min, because the former condition might have the XOS at a low degree of polymerization with a high XOS ratio (67.6%), while the latter condition presented a high glucose to total sugar ratio (91.4%) with a moderate level XOS ratio (64.4%). Although it was challenging to conclude on the autohydrolysis conditions required to obtain the best result of XOS content and purity and glucose yield, this study presented approaches that could maximize the desired product from SSB, and additional processes to reduce these differences in conditions may warrant further research.

This study deals with the development and mechanical characterization of innovative starch- and gelatin-based hydrogels enriched with hydrothermal aqueous extracts from Paulownia (i.e., bark, leaves, petioles). The color, rheology, and texture properties of formulated biopolymer-based hydrogels depending on the processing conditions of the extracts was evaluated for the different Paulownia fractions. Results indicated that a clear impact on color features of the tested hydrogels was observed with the incorporation of Paulownia extracts. Rheological testing showed that weak and intermediate strength hydrogels were identified for starch- and gelatin-based hydrogels independently of used extract. A relevant softening of all gelled matrices was observed in the presence of recovered liquor extracts involving the following trend (leaves > barks > petioles). For all fractions, the highest viscoelastic features were achieved for hydrogels made with extracts recovered at 140 °C. Texture outcomes confirmed the rheological achievements. No syneresis was observed in developed hydrogels after two weeks of cold storage.

The chemical industry is being forced to evaluate new strategies for more effective utilization of renewable feedstocks to diminish the use of fossil resources. In this literature review, the integration of both acidic and alkaline pretreatment phases of hardwood and softwood chips with chemical pulping is discussed. Depending on the pretreatment conditions, high-volume sulfur-free fractions with varying chemical compositions can be produced. In case of acidic pretreatments, the major products include carbohydrates (mono-, oligo-, and polysaccharides), whereas under alkaline (i.e., aqueous NaOH) pretreatment conditions, the sulfur-free fractions of aliphatic carboxylic acids, lignin, and extractives are primarily obtained. All these fractions are potentially interesting groups of compounds and can be used in a number of applications. Finally, the effects of pretreatments on pulping are also considered. Although it is believed that there are important advantages to be gained by integrating this type of renewable raw material-based production, in particular, with kraft pulping, sulfur-free pulping methods such as soda-AQ and oxygen/alkali delignification processes are also briefly discussed.

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.

Recovered papers are suitable biomass sources for conversion into sugars that can be used in bioethanol production. However, paper materials with a high lignin content have been found to be recalcitrant to enzymatic hydrolysis. To address this issue, several biomass pretreatment methods were employed to evaluate their efficiency on the conversion of newspaper with high lignin content to sugar. Autohydrolysis, a hot water treatment, was identified to adversely affect sugar conversion, presumably as a result of pore collapse under high-temperature pretreatment. Flexo ink, used in newspaper printing, had no effect on the enzymatic hydrolysis, with or without autohydrolysis. The ink was still detachable after autohydrolysis, as measured by hyperwashing. Compared to untreated newspaper, separate treatments of either mechanical refining or a non-ionic surfactant (sorbitan polyoxyethylene monooleate) improved the sugar conversion by 10% at enzyme dosages of 2 and 8 FPU/g substrate. The combination of both refining and surfactant resulted in the highest sugar conversions, i.e., 46.3%, 56.7%, and 64.1% at 2, 4, and 8 FPU/g enzyme dosages, respectively. Oxidative pretreatment (oxygen, 100 °C) marginally increased the sugar conversion, whereas alkaline and green liquor (NaCO3 and Na2S) pretreatments (at 160 °C) had either no effect or decreased the sugar conversion. Based on the results of the pretreatments, higher pretreatment temperatures of newsprint negatively impacted subsequent enzyme hydrolysis.

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.

Abstract Corncob was successively pretreated by liquid hot water (LHW) and ethanol organosolv (EO) in an integrated process. LHW was performed at 200 °C for 30 min, and EO was performed using uncatalyzed ethanol–water solutions, according to a design of experiments. The effects of the most influential operational variables (ethanol concentration, temperature and time) on yield and chemical composition of the fractions were assessed. Results showed the factor with the greatest effect was ethanol concentration (p < 0.05), leading to a high-purity lignin (86.7%–93.1%) with a total phenolic content of around 25 mg GAE/g. Moreover, the solids recovered from the high ethanol concentration conditions presented the lowest lignin contents (15.4%–17.2%) with good preservation of cellulose (82.5%–88.6% of glucans). The lignin antioxidant capacity showed that all lignin samples presented radical scavenging activity (IC 50 of 0.17 mg/mL and 0.016 mg/mL on DPPH (2,2‑diphenyl‑1‑picrylhydrazyl) and ABTS (2,2′‑azino‑bis(3‑ethylbenzothiazoline‑6‑sulphonic acid) assays, respectively) with values close to the commercial antioxidant BHT. Moreover, the chemical (FTIR) and thermal (DSC and TGA) characterization showed lignins with similar properties that were compared with lignin from direct ethanol organosolv process. Results showed that the integrated process of LHW-EO was the most effective way to obtain lignin with high purity and antioxidant capacity. Highlights • The integrated process was more effective in lignin extraction than the direct organosolv process; • The integrated process led to a high purity lignin and a good preservation of the cellulose fraction; • The integrated process recovered lignin with enhanced antioxidant capacity. [ABSTRACT FROM AUTHOR]

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]

Highlights • The efficiency of autohydrolysis was enhanced by adding metal chloride. • Buffering capacity of pretreated WWS was reduced by adding metal chloride. • The destruction of buffer system was attributed to cation exchange by adding metal chloride. Abstract High ash content of waste wheat straw (WWS) is resistant to biorefinery autohydrolysis pretreatment due to its self-buffering effects. In this work, minor addition FeCl 3 and AlCl 3 were applied to overcome the self-buffering effects of WWS by cationic occupation of the negatively charged sites present on particulate ash's surface. The results showed that with the increasing concentrations (0–20 mM) of AlCl 3 and FeCl 3 , the enzymatic efficiencies of autohydrolyzed WWS were enhanced from 49.7% to 62.1% and 66.6%, respectively. Acid buffer and cation exchange capacity of pretreated WWS were decreased by adding metal chlorides and the reducing results were mainly attributed to cation exchange. Meanwhile, a maximum monosaccharide production (185.3 mg/g-WWS) was achieved with 62.0 mg/g-WWS xylooligosaccharide by using 20 mM FeCl 3 during WWS autohydrolysis. The results demonstrated that the implications of FeCl 3 and AlCl 3 in WWS autohydrolysis were an effective strategy to enhance autohydrolysis efficiency by overcoming self-buffering effects. [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 aim of this work was to study acetyl-assisted autohydrolysis of sugarcane bagasse for the production of xylo-oligosaccharides without additional chemicals. A xylo-oligosaccharide yield of 50.35% was obtained in 10 min through sugarcane bagasse autohydrolysis at 200 °C; this yield was 49.64% after acetyl-assisted autohydrolysis of a 65:35 mixture of sugarcane bagasse/white birch at 160 °C for 100 min. The yield of xylo-oligosaccharides was close to that obtained at 180 °C/40 min and 200 °C/10 min through the autohydrolysis of sugarcane bagasse. Compared to sugarcane bagasse alone, the xylo-oligosaccharide (degree of polymerization 2–5) yield from the acetyl-assisted autohydrolysis at 200 °C for 10 min was 52.99%. In addition, the yield of glucose from the solid residue following autohydrolysis pretreatment was 96.87% after 72 h of enzymatic hydrolysis. These results demonstrate that acetyl-assisted autohydrolysis is a promising method for the production of xylo-oligosaccharides. [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]