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The authors are grateful to the “Ministerio de Economía y Competitividad” (Project CTQ2013-42006-R) for financial support., Se estudió la extracción de hemicelulosa de la madera de pino aplicando un tratamiento de autohidrólisis. Se realizó un diseño Se realizó un diseño experimental compuesto central utilizando diferentes temperaturas (150-190 °C) y tiempos (30-90 min) para seleccionar las condiciones de operación más favorables para maximizar la extracción de hemicelulosa y minimizar su degradación. su degradación. Esta fase líquida se analizó por HPLC para cuantificar oligosacáridos, monosacáridos y productos de degradación. La composición de la madera autohidrolizada se determinó y caracterizó mediante FTIR y TGA. Se extrajo el 60% de las hemicelulosas a una temperatura de 170 °C en 60 min, presentándose principalmente en forma oligomérica en la fase líquida, permaneciendo la fase sólida enriquecida en celulosa y lignina., The extraction of hemicellulose from pine wood was studied by applying autohydrolysis treatment. A central composite experimental design was carried out using different temperatures (150–190 °C) and times (30–90 min) to select the most favorable operating conditions for maximizing the extraction of hemicellulose and minimizing its degradation. This liquid phase was analyzed by HPLC to quantify oligosaccharides, monosaccharides and degradation products. The composition of the autohydrolyzed wood was determined and characterized, employing FTIR and TGA. Herein, 60% of the hemicelluloses were extracted under a temperature of 170 °C in 60 min, presenting primarily in an oligomeric form in the liquid phase, with the solid phase remaining enriched in cellulose and lignin., Ministerio de Economía y Competitividad, Depto. de Ingeniería Química y de Materiales, Fac. de Ciencias Químicas, TRUE, pub

The effect of autohydrolysis (AH) temperature (165 °C, 195 °C, 225 °C) on the structure, purity, and recovery yield of the cellulose residue isolated after additional alkaline and bleaching steps from wheat straw, was investigated. The processes were quantified for mass yields in the different steps and for antioxidants and sugars release during AH. AH at 195 °C allowed for the highest cellulose residue yield (83.5%) with purity (∼70%) and structure similar to the other residues. FTIR and XRD analyses showed straw cellulose (SC) with a type II polymorphism and crystallinity index increasing with AH temperature. SC obtained at the end of the entire fractionation process (SC-195 °C) starting from AH residue-195 °C was tested as a reinforcing agent in different percentage (0, 2 and 5% by weight) in poly(butylene adipate-co-terephthalate) (PBAT) films. The Young’s modulus of the films increased by ∼17% with 5 wt% cellulose, while tensile strength and elongation at break decreased.

The effect of autohydrolysis (AH) temperature (165 °C, 195 °C, 225 °C) on the structure, purity, and recovery yield of the cellulose residue isolated after additional alkaline and bleaching steps from wheat straw, was investigated. The processes were quantified for mass yields in the different steps and for antioxidants and sugars release during AH. AH at 195 °C allowed for the highest cellulose residue yield (83.5%) with purity (∼70%) and structure similar to the other residues. FTIR and XRD analyses showed straw cellulose (SC) with a type II polymorphism and crystallinity index increasing with AH temperature. SC obtained at the end of the entire fractionation process (SC-195 °C) starting from AH residue-195 °C was tested as a reinforcing agent in different percentage (0, 2 and 5% by weight) in poly(butylene adipate-co-terephthalate) (PBAT) films. The Young's modulus of the films increased by ∼17% with 5 wt% cellulose, while tensile strength and elongation at break decreased.

Liquid hot water pretreatment is considered to be a promising method for increaing biomass digestibility due to the moderate operational conditions without chemical additionA necessary step towards the scalability of this pretreatment process is performing pilot plant triaUpscaling was evaluated with a scaling factor of 500, by using 50 mL in the laboratory and 25 L in pilot plant batch reactor. Pretreatment times were varied from 30 to 240 min, and temperatures usewere 180–188◦ C, while applying similar heating profiles at both scales. The initial mass fraction poplar wood chips ranged from 10% to 16%. Liquid hot water pretreatment at laboratory and pilscale led to analogous results. The acetic acid analysis of the liquid and solid fractions obtained aftpretreatment indicated that complete deacetylation of poplar biomass can be achieved., BT/Bioprocess Engineering

Thermochemical and fractionation processes are promising ways for energy valorization and recovery of biomass and waste. An example is given by the application of a lignocellulosic fractionation process to recover both antioxidant phenolic compounds and cellulose from wheat straw, where a first hydrolysis step is carried out as a novel and green auto-hydrolysis process instead of conventional mild acid hydrolysis. Regarding this, the development of kinetic and reactor models that can represent the autohydrolysis process is crucial to exploit the potential of the agricultural residues (e.g., wheat straw). Several mathematical models were investigated, but the more suitable models for optimization purposes seem to be those based on a non-isothermal kinetic model. However, these models have several shortcomings. For instance, in the autohydrolysis process for the recovery of cellulose and lignin from by-products, the heating and cooling phases are not taken into account. Hence, from the point of view of energy optimization, closely linked also to economical optimization, this aspect becomes extremely important. Therefore, the aim of this work was to briefly present and comment, similarly to review work, the severity factor model and the kinetic model already investigated in the scientific literature in order to enable their comparison with the newly developed method in the current work in terms of different key performance indicators (e.g., cellulose recovery or sugar release). Specifically, our model includes new equations that consider both heating and cooling phases during autohydrolysis of wheat straw, as well as the isothermal step. In this way, it could be possible to use the obtained kinetic parameters not only for a specific case but also for different situations involving a wide range of operating conditions.

In the present work, the extraction and characterization of polysaccharides derived from bay tree pruning waste and their upgrading into methyl levulinate (MLA) are reported. The extraction was carried out by autohydrolysis under different conditions. The obtained fractions were characterized in terms of carbohydrates, phenolic acids, and proteins as well as in terms of molecular weight distribution. Optimum extraction conditions were found to be 160 degrees C for 45 min, and the polysaccharide fraction was found to be mainly composed of glucose (181.30 mg/ g), xylose (172.41 mg/g), and galactose (45.44 mg/g). These carbohydrates presented a number-average molar mass (Mn) of 6.04 KDa and a weight-average molar mass (Mw) of 183.4 KDa. In addition, their phenolic acids were mostly p-coumaric and ferulic acids (0.60 and 0.12 mg/g, respectively). The catalytic conversion of bay tree polysaccharides into MLA using a simple catalyst such as Al-2(SO4)(3) was subsequently conducted under microwave irradiation. Optimum reaction conditions produced up to 40 wt % of MLA., QC 20200909

Two previous treatments have been applied to the ethanol-soda paste process on Eucalyptus globulus wood to evaluate its influence on the properties of the obtained cellulose pulps. The treatments consisted of a first optimized stage of autohydrolysis (temperature: 180 ºC, time: 30 min) to obtain the maximum extraction rate of hemicellulosic derivatives preserving the glucan, followed by enzymatic oxidative delignification by a laccase/mediator system (syringaldehyde). Experimental designs have been applied for the optimization of processes. The optimum operating conditions in the enzymatic delignification stage were: Lacasse concentration 18,5 U/g, concentration of syringaldehyde 1,5 %, temperature 45 ºC and operating time 60 min., with which an elimination of the 16,8% of the existing lignin in the raw material and slightly affects the glucan (it is conserved between 82,2 % and 89,7 % of the initial glucan). Two liquid, recoverable phases are obtained, rich in hemicellulose and polyphenolic derivatives. In this process scheme to obtain ethanol-soda cellulosic pulp from eucalyptus wood requires a lower concentration of chemical reagents, shorter operating times and lower temperatures, which is an economic and environmental improvement over the conventional pulping process., Se han aplicado dos tratamientos previos al proceso de pasteado etanol-sosa sobre madera de Eucalyptus globulus para evaluar su influencia sobre las propiedades de las pastas celulósicas obtenidas. Se aplica una primera etapa optimizada de autohidrólisis para maximizar la extracción de derivados hemicelulósicos preservando el glucano, seguida de una deslignificación enzimática mediante un sistema lacasa/mediador (siringaldehído). Se aplican diseños experimentales para la optimización de los procesos. Las condiciones de operación óptimas en la etapa de deslignificación enzimática han sido: concentración de lacasa 18,5 U/g, concentración de siringaldehído 1,5 %, temperatura 45 ºC y tiempo de operación 60 min., con las cuales se alcanza una eliminación del 16,8 % de la lignina existente en la materia prima y se afecta ligeramente al glucano (conservando entre el 82,2 % y 89,7 % del glucano inicial). Paralelamente se obtienen dos fases líquidas valorizables, ricas en derivados hemicelulósicos y polifenólicos. En este esquema de proceso para obtención de pasta celulósica etanol-sosa a partir de madera eucalipto requiere una menor concentración de reactivos químicos, menores tiempos de operación y temperaturas más bajas, lo que supone una mejora económica y medioambiental respecto del proceso convencional de pasteado.

Two previous treatments have been applied to the ethanol-soda paste process on Eucalyptus globulus wood to evaluate its influence on the properties of the obtained cellulose pulps. The treatments consisted of a first optimized stage of autohydrolysis (temperature: 180 ºC, time: 30 min) to obtain the maximum extraction rate of hemicellulosic derivatives preserving the glucan, followed by enzymatic oxidative delignification by a laccase/mediator system (syringaldehyde). Experimental designs have been applied for the optimization of processes. The optimum operating conditions in the enzymatic delignification stage were: Lacasse concentration 18,5 U/g, concentration of syringaldehyde 1,5 %, temperature 45 ºC and operating time 60 min., with which an elimination of the 16,8% of the existing lignin in the raw material and slightly affects the glucan (it is conserved between 82,2 % and 89,7 % of the initial glucan). Two liquid, recoverable phases are obtained, rich in hemicellulose and polyphenolic derivatives. In this process scheme to obtain ethanol-soda cellulosic pulp from eucalyptus wood requires a lower concentration of chemical reagents, shorter operating times and lower temperatures, which is an economic and environmental improvement over the conventional pulping process., Se han aplicado dos tratamientos previos al proceso de pasteado etanol-sosa sobre madera de Eucalyptus globulus para evaluar su influencia sobre las propiedades de las pastas celulósicas obtenidas. Se aplica una primera etapa optimizada de autohidrólisis para maximizar la extracción de derivados hemicelulósicos preservando el glucano, seguida de una deslignificación enzimática mediante un sistema lacasa/mediador (siringaldehído). Se aplican diseños experimentales para la optimización de los procesos. Las condiciones de operación óptimas en la etapa de deslignificación enzimática han sido: concentración de lacasa 18,5 U/g, concentración de siringaldehído 1,5 %, temperatura 45 ºC y tiempo de operación 60 min., con las cuales se alcanza una eliminación del 16,8 % de la lignina existente en la materia prima y se afecta ligeramente al glucano (conservando entre el 82,2 % y 89,7 % del glucano inicial). Paralelamente se obtienen dos fases líquidas valorizables, ricas en derivados hemicelulósicos y polifenólicos. En este esquema de proceso para obtención de pasta celulósica etanol-sosa a partir de madera eucalipto requiere una menor concentración de reactivos químicos, menores tiempos de operación y temperaturas más bajas, lo que supone una mejora económica y medioambiental respecto del proceso convencional de pasteado.

Two previous treatments have been applied to the ethanol-soda paste process on Eucalyptus globulus wood to evaluate its influence on the properties of the obtained cellulose pulps. The treatments consisted of a first optimized stage of autohydrolysis (temperature: 180 ºC, time: 30 min) to obtain the maximum extraction rate of hemicellulosic derivatives preserving the glucan, followed by enzymatic oxidative delignification by a laccase/mediator system (syringaldehyde). Experimental designs have been applied for the optimization of processes. The optimum operating conditions in the enzymatic delignification stage were: Lacasse concentration 18,5 U/g, concentration of syringaldehyde 1,5 %, temperature 45 ºC and operating time 60 min., with which an elimination of the 16,8% of the existing lignin in the raw material and slightly affects the glucan (it is conserved between 82,2 % and 89,7 % of the initial glucan). Two liquid, recoverable phases are obtained, rich in hemicellulose and polyphenolic derivatives. In this process scheme to obtain ethanol-soda cellulosic pulp from eucalyptus wood requires a lower concentration of chemical reagents, shorter operating times and lower temperatures, which is an economic and environmental improvement over the conventional pulping process., Se han aplicado dos tratamientos previos al proceso de pasteado etanol-sosa sobre madera de Eucalyptus globulus para evaluar su influencia sobre las propiedades de las pastas celulósicas obtenidas. Se aplica una primera etapa optimizada de autohidrólisis para maximizar la extracción de derivados hemicelulósicos preservando el glucano, seguida de una deslignificación enzimática mediante un sistema lacasa/mediador (siringaldehído). Se aplican diseños experimentales para la optimización de los procesos. Las condiciones de operación óptimas en la etapa de deslignificación enzimática han sido: concentración de lacasa 18,5 U/g, concentración de siringaldehído 1,5 %, temperatura 45 ºC y tiempo de operación 60 min., con las cuales se alcanza una eliminación del 16,8 % de la lignina existente en la materia prima y se afecta ligeramente al glucano (conservando entre el 82,2 % y 89,7 % del glucano inicial). Paralelamente se obtienen dos fases líquidas valorizables, ricas en derivados hemicelulósicos y polifenólicos. En este esquema de proceso para obtención de pasta celulósica etanol-sosa a partir de madera eucalipto requiere una menor concentración de reactivos químicos, menores tiempos de operación y temperaturas más bajas, lo que supone una mejora económica y medioambiental respecto del proceso convencional de pasteado.

Two previous treatments have been applied to the ethanol-soda paste process on Eucalyptus globulus wood to evaluate its influence on the properties of the obtained cellulose pulps. The treatments consisted of a first optimized stage of autohydrolysis (temperature: 180 ºC, time: 30 min) to obtain the maximum extraction rate of hemicellulosic derivatives preserving the glucan, followed by enzymatic oxidative delignification by a laccase/mediator system (syringaldehyde). Experimental designs have been applied for the optimization of processes. The optimum operating conditions in the enzymatic delignification stage were: Lacasse concentration 18,5 U/g, concentration of syringaldehyde 1,5 %, temperature 45 ºC and operating time 60 min., with which an elimination of the 16,8% of the existing lignin in the raw material and slightly affects the glucan (it is conserved between 82,2 % and 89,7 % of the initial glucan). Two liquid, recoverable phases are obtained, rich in hemicellulose and polyphenolic derivatives. In this process scheme to obtain ethanol-soda cellulosic pulp from eucalyptus wood requires a lower concentration of chemical reagents, shorter operating times and lower temperatures, which is an economic and environmental improvement over the conventional pulping process., Se han aplicado dos tratamientos previos al proceso de pasteado etanol-sosa sobre madera de Eucalyptus globulus para evaluar su influencia sobre las propiedades de las pastas celulósicas obtenidas. Se aplica una primera etapa optimizada de autohidrólisis para maximizar la extracción de derivados hemicelulósicos preservando el glucano, seguida de una deslignificación enzimática mediante un sistema lacasa/mediador (siringaldehído). Se aplican diseños experimentales para la optimización de los procesos. Las condiciones de operación óptimas en la etapa de deslignificación enzimática han sido: concentración de lacasa 18,5 U/g, concentración de siringaldehído 1,5 %, temperatura 45 ºC y tiempo de operación 60 min., con las cuales se alcanza una eliminación del 16,8 % de la lignina existente en la materia prima y se afecta ligeramente al glucano (conservando entre el 82,2 % y 89,7 % del glucano inicial). Paralelamente se obtienen dos fases líquidas valorizables, ricas en derivados hemicelulósicos y polifenólicos. En este esquema de proceso para obtención de pasta celulósica etanol-sosa a partir de madera eucalipto requiere una menor concentración de reactivos químicos, menores tiempos de operación y temperaturas más bajas, lo que supone una mejora económica y medioambiental respecto del proceso convencional de pasteado.

The valorisation and the reuse of agricultural residue and food waste are gaining more attention in the last years as are directly related to environmental sustainability. For this reason, the aim of this study is to evaluate the influence of autohydrolysis operating conditions for a high yield recovery of sugars, soluble fiber and antioxidants from grape skins. In this work, an experimental campaign using a lab-scale batch autohydrolysis reactor is scheduled based on statistical methods to assess the influence of some process variables (like water to skins solids ratio or working temperaure) on some selected key performance indicators (KPIs), like sugars, sugar degradation products, phenolic compounds, antioxidant compounds and fiber recovery. As a comparison, different agricultural residue, like wheat straw, are considered. Entering in the details, the volume of the recovered autohydrolysis liquid fraction is measured and analyzed to calculate the release yield of both total solids and specific components, including antioxidant activity according different in vitro assays tests such as and ABTS assay. Therefore, this work presents an innovate autohydrolysis process for the valorization of waste grape skins for the production of added-value compounds through a potentially green technology.

Wheat straw (WS) is an agricultural residue that presents many interesting characteristics that facilitate its biotechnological upgrade in a bio-refinery framework [1]. Based on the data from FAO, world annual WS production is about 577 million tons in 2016 and is supposed to be higher in the next years. Plant cell walls of wheat straw are formed with a polysaccharide network of which cellulose, hemicelluloses and pectin are the most important components [2].

Wheat straw (WS) is an agricultural residue that presents many interesting characteristics that facilitate its biotechnological upgrade in a bio-refinery framework [1]. Based on the data from FAO, world annual WS production is about 577 million tons in 2016 and is supposed to be higher in the next years. Plant cell walls of wheat straw are formed with a polysaccharide network of which cellulose, hemicelluloses and pectin are the most important components [2].

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

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.

Xylan extracted from rapeseed straw was chemically modified to gain hydrophobic and thermoplastic properties via macroinitiator formation followed by a free radical grafting-from polymerization with octadecyl acrylate. Biocomposites were then prepared by incorporation of 5 or 20% (w/w) rapeseed straw xylan into a poly(ε-caprolactone) (PCL) matrix by melt extrusion. The grafted xylan was homogeneously distributed within the biocomposite and reinforced the PCL matrix while at the same time preserving the ability to elongate to tensile strains >500%. Analogous biocomposites made from unmodified xylan in a PCL matrix resulted in heterogeneous mixtures and brittle tensile properties.

Xylan extracted from rapeseed straw was chemically modified to gain hydrophobic and thermoplastic properties via macroinitiator formation followed by a free radical grafting-from polymerization with octadecyl acrylate. Biocomposites were then prepared by incorporation of 5 or 20% (w/w) rapeseed straw xylan into a poly(ε-caprolactone) (PCL) matrix by melt extrusion. The grafted xylan was homogeneously distributed within the biocomposite and reinforced the PCL matrix while at the same time preserving the ability to elongate to tensile strains >500%. Analogous biocomposites made from unmodified xylan in a PCL matrix resulted in heterogeneous mixtures and brittle tensile properties.

Xylan extracted from rapeseed straw was chemically modified to gain hydrophobic and thermoplastic properties via macroinitiator formation followed by a free radical grafting-from polymerization with octadecyl acrylate. Biocomposites were then prepared by incorporation of 5 or 20% (w/w) rapeseed straw xylan into a poly(ε-caprolactone) (PCL) matrix by melt extrusion. The grafted xylan was homogeneously distributed within the biocomposite and reinforced the PCL matrix while at the same time preserving the ability to elongate to tensile strains >500%. Analogous biocomposites made from unmodified xylan in a PCL matrix resulted in heterogeneous mixtures and brittle tensile properties.

Rapeseed straw consists of a hard epidermis that is rich in hemicellulose and lignin and a sponge-like interior that consists mainly of cellulose. The stems were subjected to water, alkali or acid as extraction medium. The effects of the extraction conditions were quantified using severity factors and by comparing the effects of different extraction pHs, temperatures and times. Extraction with alkali resulted in a higher yield, 47 g/100 g straw in, compared to water, 6 g/100 g straw in, or an acidic, 5 g/100 g straw in, extraction process. An increase in temperature improved the extraction yield; in particular, more xylan was extracted at an elevated temperature and higher alkalinity. However, at high alkalinity, increased extraction temperatures led to a reduction in the recovery of glucomannan. The highest molecular weights (similar to 35,000 g/mol) of the extracted hemicelluloses were obtained using extraction procedures with 1.5 M NaOH at 110 degrees C and autohydrolysis at 150 degrees C. While these two parameter settings had very similar severity factors, extraction under basic conditions afforded an extract rich in xylan and low in lignin content, whereas autohydrolysis generated a glucomannan-rich extract., QC 20170202

Hydrothermal extraction of hemicelluloses from lignocellulosic biomass for conversion to renewable materials or fuels has captured attention. The extraction is however partial and some lignin is codissolved. Herein, we investigated the role of molecular structure in the recalcitrance. Wood meal of Spruce and Birch were subjected to pressurized hydrothermal extraction at 160 °C for 2 h, which extracted 68–75% of the hemicelluloses. 2D heteronuclear single quantum coherence (HSQC) NMR, HSQC-TOCSY, and 13C NMR were applied for structural studies of both extracts and residues. Subsequent to the known partial hydrolysis of native carbon-2 and carbon-3 acetates in hemicellulose, some acetylation of primary alcohols on hemicelluloses and lignin was observed. Lignin carbohydrate complexes (LCC) were detected in both the extracts and residues. In Spruce extracts, only the phenyl glycoside-type of LCC was detected. Birch extracts contained both the phenyl glycoside and benzyl ether-types. In the hydrothermal wood residues of both species, benzyl ether- and gamma (γ)-ester-LCC were present. Structural changes in lignin included decrease in aryl ether (βO4) content and increases in resinol- (ββ) and phenyl coumaran (β5) contents. On the basis of the overall analysis, the mechanisms and contribution of molecular structure to recalcitrance is discussed., QC 20170613

The aim of this work was to compare the two most common hydrothermal pre-treatments for wood – mild steam explosion and hot water extraction – both with the prospect of enabling extraction of hemicelluloses and facilitating further processing. Although both involve autohydrolysis of the lignocellulosic tissue, they are performed under different conditions: the most prominent difference is the rapid, disintegrating, discharge employed in the steam explosion opening up the structure. In this comparative study, the emphasis was placed on local composition of the pre-treated wood chips (of industrially relevant size). The results show that short hot water extraction treatments lead to significant variations in the local composition within the wood chips, while steam explosion accomplishes a comparably more even removal of hemicelluloses due to the advective mass transport during the explosion step., QC 20170621

Polymeric hemicelluloses were extracted by autohydrolysis and alkali from a biomass feed consisting of the stems of rapeseed straw according to a full statistical factorial screening design. Water extraction yielded fractions rich in galactoglucomannan, while alkaline extraction yielded primarily xylan. The extracted galactoglucomannan and xylans had similar molecular weights, while the yield of xylan was higher than the yield of galactoglucomannan. The extracted hemicellulose fractions also contained some lignin (7-15%) and traces of Ca, K, Na, and Si. Free-standing films were prepared from the hemicellulose fractions with different xylan:galactoglucomannan ratios. The rapeseed xylan films showed strain-to-break values >60% without any added plasticizers., QC 20151113

Eucalyptus globulus wood chips were subjected to autohydrolysis pretreatment at 175ºC at three different residence times. Part of the recovered solids were submitted to alkaline extraction with NaOH solution to remove leachable lignin. The chemical composition of the fibrous material was analyzed by HPLC, Py-GCMS and 2D-NMR HSQC, while morphological changes were evaluated by SEM and LSCM. The pretreated materials were hydrolyzed with cellulases at a substrate loading of 10% (w/v) for up to 72 h. Glucose yields (based on dry wood) obtained in the enzymatic hydrolysis ranged between 38% and 65%, depending on reaction time in the autohydrolysis pretreatment. After the alkaline extraction, no significant change was observed in the yields in the enzymatic hydrolysis at 72 h, but at the lower severities, the initial rates of saccharification increased. The main effect of the hydrothermal pretreatment was removal of hemicelluloses, resulting in enriched cellulose pulps. SEM and LSCM images of the hydrothermal pretreated samples showed a disruption of the fiber surface, mainly in those samples obtained at the higher severity. Py-GC/MS and HSQC analysis showed that no major changes in the lignin structure occurred in the samples obtained by autohydrolysis and further alkaline extraction. By autohydrolysis at the higher severity (So=4.02), the lateral chains in lignin were cleaved and the formation of lignin droplets was observed. Hemicelluloses removal and lignin redeposition as droplets in certain regions of the fiber surface was associated with the higher accessibility of cellulose and the yield increase of the enzymatic hydrolysis.

Growing interest in alternative and renewable energy sources has brought increasing attention to the integration of a pulp mill into a forest biorefinery, where other products could be produced in addition to pulp. To achieve this goal, hemicelluloses were extracted, either by steam explosion or by steam treatment, from Eucalyptus globulus wood prior to pulping. The effects of both pre-treatments in the subsequent kraft pulping and paper strength were evaluated. Results showed a similar degree of hemicelluloses extraction with both options (32-67% of pentosans), which increased with the severity of the conditions applied. Although both pre-treatments increased delignification during pulping, steam explosion was significantly better 12.9 kappa number vs 22.6 for similar steam unexploded pulps and 40.7 for control pulp. Finally, similar reductions in paper strength were found regardless of the type of treatment and conditions assayed, which is attributed to the increase of curled and kinked fibers. © 2013 Elsevier Ltd.

Steam explosion and steam pre-treatment have proved capable of enhancing enzymatic saccharification of lignocellulosic materials. However, until now, these methods had not been compared under the same operational conditions and using the same raw material. Both pre-treatments lead to increased yields in the saccharification of Eucalyptus globulus; but results have been better with steam pre-treatments, despite the more accessible surface of exploded samples. The reason for this finding could be enzymatic inhibition steam explosion causes a more extensive extraction of hemicelluloses and releases a greater amount of degradation products which can inhibit enzymatic action. Enzymatic inhibition is also dependent on the amount and chemical structure of lignin, which was also a contributing factor to the lower enzymatic yields obtained with the most severe pre-treatment. Thus, the highest yields (46.7% glucose and 73.4% xylose yields) were obtained after two cycle of steam treatment, of 5 and 3. min, at 183. °C. © 2014 Elsevier Ltd.

Polymeric phenolic fraction (PPF) was isolated by ethyl acetate extraction from hydrolyzed liquids from steam-treated alperujo and characterized. PPF is composed mainly of phenolic compounds with small amounts of carbohydrates, protein and ash. Phenols such as hydroxytyrosol (HT) and tyrosol were bound to PPF during the ethyl acetate extraction. Acid hydrolysis (3. N HCl for 10. min at 100. °C) was used to liberate HT from the PPF. The properties of both sorption and desorption of the PPF were studied to enhance the purification of HT, up to 100%. The antioxidant activities of the PPF were evaluated in vitro using ferric reducing power and DPPH radical scavenging, showing activity but lower than HT and TROLOX. The inhibition of primary oxidation of PPF was similar to both HT and vitamin E. These antioxidant activities of the PPF were not a result of the presence of HT or similar phenols. © 2013 Elsevier Ltd.

A combination of two environment-friend processes for hemicelluloses and lignin recovery from red grape stalks were investigated: an autohydrolysis pretreatment at 180 C for 30 min followed by a non-catalysed ethanol organosolv step at 180 C for 90 min. Hemicelluloses were precipitated by ethanol addition to autohydrolysis liquor, while lignin was tentatively precipitated by acidification of liquors from both the processes. Results suggest that stalks hemicelluloses can be easily hydrolysed requiring a milder treatment to reduce sugar degradation, while the organosolv process did not give a consistent delignification. Autohydrolysis allowed a recovery of 2% (on stalks d.m.) of total phenols in the liquor. Organosolv liquor had a higher concentration of phenols (corresponding to 0.72% of stalks d.m.) which almost completely precipitated with lignin.

A combination of two environment-friend processes for hemicelluloses and lignin recovery from red grape stalks were investigated: an autohydrolysis pretreatment at 180 C for 30 min followed by a non-catalysed ethanol organosolv step at 180 C for 90 min. Hemicelluloses were precipitated by ethanol addition to autohydrolysis liquor, while lignin was tentatively precipitated by acidification of liquors from both the processes. Results suggest that stalks hemicelluloses can be easily hydrolysed requiring a milder treatment to reduce sugar degradation, while the organosolv process did not give a consistent delignification. Autohydrolysis allowed a recovery of 2% (on stalks d.m.) of total phenols in the liquor. Organosolv liquor had a higher concentration of phenols (corresponding to 0.72% of stalks d.m.) which almost completely precipitated with lignin.

[EN]A study of the potential of autohydrolysis and alkaline extraction processes from corn stalks was performed for high purity hemicellulose extraction. The influence of process parameters on the purity of obtained hemicelluloses was analyzed. An experimental design was developed for the autohydrolysis treatments to determine the optimal conditions to solubilize the hemicelluloses with lowest content in contaminants. On the other hand, alkaline extraction, including raw material pretreatment (dewaxing and delignification step) was carried out analyzing the effectiveness of this processes for maximum pure hemicellulose recovery. The maximum yield (54% of the raw material hemicelluloses) and the best physicochemical properties (highest hemicellulose content free of lignin) were obtained with these pretreatments in alkaline extraction. Moreover, the effect of lignin removal by sulfuric acid from the autohydrolysis liquors before hemicellulose precipitation was studied. This purification step has allowed to obtain lignin-free autohydrolysis hemicellulose but with the presence of sulfur as predominant contaminant.

The aim of this research is to separate different wood components from softwood as a first step towards development of novel materials made from Scandinavian wood. The approach is pre-treatment with a reducing agent in combination with mild steam explosion (T< 160°C, t < 15 min); followed by extraction with different liquors. The aim is to retain an increased amount of hemicelluloses in general, and glucomannans in particular, during chemical treatments, preferably of high molecular weight. Experiments were performed on wood chips from spruce in small scale steam explosion equipment. A pre-treatment method with sodium borohydride (NaBH 4) as a reducing agent model substance was chosen. Wood chips pre-treated with NaBH 4 were compared to untreated chips, and the chips were treated with steam explosion followed by extraction in alkali. Results showed that a higher amount of glucomannan was retained in chips treated with NaBH 4 than in untreated chips. An increase in the extraction rate as an effect of steam explosion indicates a possible combination of chemical reactions that breaks up the lignin-polysaccharide network and a more porous wood structure. An experimental series with wood powder as raw material were also performed in order to study the chemical reactions during steam explosion, e. g. autohydrolysis. Water impregnated wood powder as well as wood powder treated with NaBH 4 was subjected to mild steam explosion for different retention times. It was shown that a decrease in hemicelluloses content occurred after only 5 min, and the degradation was more severe at longer residence times. However, the degradation of hemicelluloses was not as severe as in the chemical treatments at conditions corresponding to chemical pulping, and consequently might be a more prudent method to access the wood structure. Extractions after steam explosion were investigated at different pH levels, and the results showed that most of the glucomannan was still in the wood, QC 20140829

Autohydrolysis using water is a promising method to extract hemicelluloses from wood prior to pulping in order to make co-products such as ethanol and acetic acid besides pulp. Many studies have been carried out on the kinetics and mechanism of autohydrolysis using batch reactors. The present study was performed in a continuous mixed flow reactor where the wood chips are retained in a basket inside the reactor. This reactor is well suited to determine intrinsic kinetics of hemicellulose dissolution because the dissolved products are rapidly removed from the reactor, thus minimizing further hydrolysis and degradation of the hemicelluloses in solution. The xylan removal rate follows an S-shaped behavior. GPC analysis of the continuously removed extract shows that the dissolved xylan oligomers have a DP smaller than about 25. Lignin-free xylan oligomers and cellulose oligomers are the major components dissolved in the initial stage of autohydrolysis, while xylan covalently bound to lignin (i.e. an LCC) is the major component removed during the later stage of autohydrolysis. The molecular weight of the dissolved components decreases with time in the second stage. The kinetics of xylan removal are explained in terms of a mechanism based on recent knowledge of the ultrastructure of the cell fibre wall., QC 20120207

Extraction of hemicelluloses from wood prior to pulping is being pursued to generate more value-added products, while still producing high quality pulp from the pre-extracted wood. For a better understanding of the factors limiting selective extraction, enzymatic hydrolysis in combination with size exclusion chromatography (SEC) was applied to milled wood and hydrothermally treated wood. Complete dissolution was achieved in a lithium chloride/dimethylacetamide solvent system after mild ball-milling of a Southern Hardwood Mixture (SHM), of SHM extracted using auto-hydrolysis, and of enzyme-treated SHM. SEC tests showed that severe degradation of wood polymers occurred after a milling time of 3 hours. The SEC data also confirmed the presence of lignin-carbohydrate complexes. Based on the results, it is suggested that linkages between lignin and polysaccharides may play an important role in limiting extraction of hemicelluloses., QC 20120201

Autohydrolysis of aspen wood breaks down lignin beta-O-4 linkages via both acidolysis and homolytical cleavage. A simultaneous repolymerization by lignin-lignin condensation is the major reason for the low degree of delignification and the poor lignin reactivity. Modification of the autohydrolysis reaction by the addition of either NaOH or 2-naphthol changes the mechanism such that less acidolysis and fewer lignin-lignin condensation reactions take place, and an almost complete delignification can be achieved. The resulting isolated lignins have a low M., a light color and still contain some of the native beta-O-4 linkages. Lignin from autohydrolysis in the presence of NaOH possesses more carboxylic acid groups, while the addition of 2-naphthol results in a lignin with a large amount of phenolic hydroxyl groups and incorporated naphthalene rings. These types of change are beneficial since the lignin structure becomes much more homogeneous with a greater potential for further upgrading and use., Conference of the National-Institute-of-Drug-Abuse-Health-Disparities Location: Atlanta, GA Date: OCT 23-26, 2005