Autohydrolysis Treatment Research Articles

Effect of autohydrolysis on Pinus radiata wood for hemicellulose extraction

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.

Valorization of Vine Shoots Based on the Autohydrolysis Fractionation Optimized by a Kinetic Approach

Nonisothermal autohydrolysis treatments of vine shoots were used as a method for hemicellulose solubilization and xylooligosaccharides (XOS) production. The proposed kinetic model allowed the selection of the operational conditions that maximize the oligosaccharides content and minimize the generation of undesired compounds such as monosaccharides and sugar-decomposition products. In this sense, the maximum value of XOS (9.9 g/100 g raw material) was obtained at 200 °C. The liquid fraction containing oligosaccharides was highly stable against heat and pH (degradation below 10%), demonstrating its potential as functional food ingredients. On the other hand, the cellulose-enriched solid fraction was subjected to enzymatic digestibility, obtaining 49.5% of total glucan hydrolysis after 96 h. In this work, the holistic use of wine shoots following a biorefinery concept has been proposed. However, a delignification step of the cellulose-enriched solid fraction should be included in order to increase the enzymatic digestibility, and hence allow the integral use of this byproduct.

Integral valorization of vine pruning residue by sequential autohydrolysis stages

Wine processing generates a large amount of residue, in particular pruning residue of vine. In this work, autohydrolysis in two sequential stages was proposed for the integral valorization of this residue. In a first stage, vine pruning residue was submitted to autohydrolysis treatment at 180 °C for 60 min (severity of 4.13) and liquid to solid ratio of 6 g water per g vine pruning residue. In these conditions, 63.7% of xylan was recovered in the liquid phase as xylooligosaccharides (17 g/L) and 2.35 g/L of phenolic compounds with antioxidant activity were also extracted. Autohydrolyzed vine pruning residue was subjected to a second autohydrolysis at temperature in the range 180–200 °C and time 30–40 min. After sequential treatments, enzymatic hydrolysis of cellulose was significantly improved from 73% to 99% of conversion. At selected conditions (severity of 4.60), ethanol production was successfully obtained from two strategies of, separately and simultaneously, saccharification and fermentation, thus achieving ethanol yield of 96 and 83%, respectively. Overall, two sequential stages of the process allowed the recovery of 13.7 kg of xylooligosaccharides, 3.1 kg of phenolic compounds, 13.1 kg of ethanol and 27 kg of lignin per 100 kg of vine pruning residue. Sequential autohydrolysis stages were shown as a suitable strategy for the integral valorization of vine pruning residue.

Production and Characterization of Organic Solvent-Tolerant Cellulase from Bacillus amyloliquefaciens AK9 Isolated from Hot Spring.

A cellulase-producing bacterium, designated as strain AK9, was isolated from a hot spring of Tatta Pani, Azad Kashmir, Pakistan. The bacterium was identified as Bacillus amyloliquefaciens through 16S rRNA sequencing. Cellulase from strain AK9 was able to liberate glucose from soluble cellulose and carboxymethyl cellulose (CMC). Enzyme was purified through size exclusion chromatography and a single band of ∼47kDa was observed on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The enzyme was purified with recovery of 35.5%, 3.6-fold purity with specific activity of 31Umg-1. The purified cellulase retained its activity over a wide range of temperature (50-70°C) and pH (3-7) with maximum stability at 60°C and pH5.0. The activity inhibited by ethylenediaminetetraacetic acid (EDTA), suggested that it was metalloenzyme. Diethyl pyrocarbonate (DEPC) and β-mercaptoethanol significantly inhibited cellulase activity that revealed the essentiality of histidine residues and disulfide bonds for its catalytic function. It was stable in non-ionic surfactants, in the presence of various metal ions, and in water-insoluble organic solvents. Approximately 9.1% of reducing sugar was released after enzymatic saccharification of DAP-pretreated agro-residue, compared to a very low percentage by autohydrolysis treatment. Hence, it is concluded that cellulase from B. amyloliquefaciens AK9 can potentially be used in bioconversion of lignocellulosic biomass to fermentable sugars.

Selecting the Pre-Hydrolysis Conditions for Eucalyptus Wood in A Fractional Exploitation Biorefining Scheme

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

Integrated approach for effective bioethanol production using whole slurry from autohydrolyzed Eucalyptus globulus wood at high-solid loadings

One of the most important targets and challenges in the second generation bioethanol is the development of a cost-effective process on large-scale. In this context, the high solid loading on saccharification and fermentation and the use of whole-slurry from pretreatment could be promising alternatives to obtain high ethanol concentrations and to decrease operational costs and wastewater. In this work, Eucalyptus globulus wood was submitted to non-isothermal autohydrolysis treatment (Tmax=210°C) and the whole-slurry obtained was assayed for the optimization of enzymatic saccharification at different solid and enzymes (CTec2 and HTec2) loadings using a Box–Behnken experimental design. Under the optimized conditions (liquid solid ratio 6.4g/g, cellulase to substrate ratio 22.5FPU/g and hemicellulase to substrate ratio 500UI/g), two strategies were evaluated for ethanol production (Simultaneous Saccharification and Fermentation, SSF and Presaccharification and Simultaneous Saccharification and Fermentation, PSSF), using an industrial and robust Saccharomyces cerevisiae strain. High concentrations of ethanol (50.2 and 48.8g/L) and productivities (0.63 and 0.55g/Lh) were obtained by SSF and PSSF, respectively. The SSF process proved to be an advantageous strategy to obtain concentrations >6% (v/v) of ethanol with elevated conversion (95%) even employing high solid loading and non-detoxified hydrolysate. Following an integrated optimization process, cost-effective bioethanol production conditions from whole-slurry E. globulus wood were determined and validated experimentally, representing a step-forward towards its industrial implementation.

Preparation of biodegradable foam from walnut shells treated by subcritical water

BACKGROUND Subcritical water treatment is considered an environment-friendly method to liquefy biomass to prepare valuable chemicals. Several researchers have studied the solid obtained after autohydrolysis treatment for use as reinforcement in biocomposities and was the base pulp and paper technologies. The novelty of this present research is the use of solid in the manufacture of starch foams. RESULTS Subcritical water was used to extract hemicellulosic carbohydrate from walnut shells at temperatures from 160 to 260 °C for 15 min and at 200 °C for various treatment times. The maximum yield was obtained at 200 °C for 15 min. The residue of the walnut shells obtained at the maximum carbohydrates extraction yield was used to prepare a biodegradable foam by compounding with corn starch using a technique similar to compression molding. It was found that replacing 20% of the corn starch by the residue had no deleterious effects on the density and morphology, as indicated by scanning electron microscopy. The prepared foams had a dense outer skin and a less dense interior with large, mostly open cells. The flexural strains were similar to that of foamed polystyrene and the flexural modulus and flexural stresses were larger. CONCLUSION It was considered that the prepared biodegradable foam was a promising material to take the place of plastic products in the future. © 2014 Society of Chemical Industry

Study of different post-hydrolysis methods to improve hemicellulosic monomers extraction

Two different post-hydrolysis methods were studied and compared with the purpose of obtaining liquid fractions with the highest concentrations of hemicellulosic monomers. With this purpose, liquors obtained from corn cobs autohydrolysis treatment were treated with different acids (sulfuric acid (H2SO4), hydrochloric acid (HCl), trifluoroacetic acid (TFA), and formic acid) as catalysts at different reaction conditions by two different hemicelluloses fractionation methods: reflux and microwave technology. In addition to different acid catalysts, catalyst concentrations, temperatures, and times of reaction were varied in all of the carried out experiments. According to the obtained results from the proposed study, the best conditions to achieve the optimum conditions for hemicelluloses fractionation were using TFA as acid catalyst in a reflux method with 4 % of catalyst concentration and at ebullition temperature (∼100 oC) and 90 min as time of reaction. Under these conditions, 32.90 ± 2.17 g/L of xylose (a yield of 87.79 ± 5.80 % of corn cobs total hemicelluloses) were solubilized.

Production and purification of xylooligosaccharides from oil palm empty fruit bunch fibre by a non-isothermal process

Oil palm empty fruit bunches (OPEFB) fibre, a by-product generated from non-woody, tropical perennial oil palm crop was evaluated for xylooligosaccharides (XOS) production. Samples of OPEFB fibre were subjected to non-isothermal autohydrolysis treatment using a temperature range from 150 to 220 °C. The highest XOS concentration, 17.6g/L which relayed from solubilisation of 63 g/100 g xylan was achieved at 210 °C and there was a minimum amount of xylose and furfural being produced. The chromatographic purification which was undertaken to purify the oligosaccharide-rich liquor resulted in a product with 74-78% purity, of which 83-85% was XOS with degree of polymerisation (DP) between 5 and 40.

Efficient removal of hexavalent chromium from aqueous solutions using autohydrolyzed Scots Pine (Pinus Sylvestris) sawdust as adsorbent

In this work, a low-cost lignocellulosic adsorbent with high biosorption capacity is proposed, suitable for the efficient removal of hexavalent chromium from water and wastewater media. The adsorbent was produced by autohydrolyzing Scots Pine (Pinus Sylvestris) sawdust. The effect of the autohydrolysis conditions, i.e., pretreatment time and temperature, on hexavalent chromium biosorption was investigated using energy-dispersive X-ray spectroscopy (EDS) and UV–visible spectrophotometry. The Freundlich, Langmuir, Sips, Radke-Prausnitz, Modified Radke-Prausnitz, Toth, UNILAN, Temkin and Dubinin-Radushkevich adsorption capacities and the rate constant values for pseudo-first- and pseudo-second-order kinetics indicated that the autohydrolyzed material exhibits significantly enhanced hexavalent chromium adsorption properties comparing with the untreated sawdust. The Freundlich’s adsorption capacity K F increased from 2.276 to 8.928 (mg g−1)(L mg−1)1/n , and the amount of hexavalent chromium adsorbed at saturation (Langmuir constant q m) increased from 87.4 to 345.9 mg g−1, indicating that autohydrolysis treatment at 240 °C for 50 min optimizes the adsorption behavior of the lignocellulosic material.

Effect of alkaline and autohydrolysis processes on the purity of obtained hemicelluloses from corn stalks

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.

Dye adsorption on autohydrolyzed pine sawdust in batch and fixed-bed systems

Batch and column kinetics of three basic dyes, methylene blue (MB), bismarck brown (BB) and acridine orange (AO), adsorption on autohydrolyzed (160–240 °C, 0–50 min) Scots pine ( Pinus sylvestris L.) sawdust were studied, using untreated pine sawdust as control, in order to explore the potential use of these low-cost industrial byproducts (untreated autohydrolyzed sawdust) for wastewater cleaning. The effect of the autohydrolysis time and temperature on the microstructure and the crystallinity of pine sawdust was investigated be means of: SEM, FTIR, XRD and BET, in order to obtain information at a higher granularity level, in comparison with previous studies. The BET surface area increased from 0.89 to 19.3 m 2 g −1. In the case of MB, the Freundlich's adsorption capacity K F increased from 5.60 to 15.7 (mg g −1)(L mg −1) 1/ n , the amount of dye adsorbed when saturation is attained (Langmuir constant q m) increased from 38.7 to 88.0 mg g −1, and the Bohart-Adams adsorption capacity coefficient N increased from 8046 to 14157 mg L −1, indicating the extent that the severity of the autohydrolysis treatment enhanced the adsorption behavior of the material.

Ultrasound-assisted fractionation of the lignocellulosic material

In the present work the effectiveness of different lignocellulosic biomass fractionation processes based on ultrasounds technology was evaluated. Organosolv (acetic acid 60% v/v), alkaline (sodium hydroxide 7.5% w/w) and autohydrolysis treatments were applied at low temperature and the fractionation effectiveness was measured at different sonication conditions of the raw material. The obtained solid fractions were characterized using TAPPI standard methods, and the liquid fractions main components were quantified with the purpose of studying the effect that the treatment conditions had on the obtained by-products quality. Therefore, obtained lignin samples were characterized by ATR-IR spectroscopy and their thermal behaviour by TGA technique. The results showed that ultrasounds application improved the yield and selectivity of the studied processes and that the obtained lignin did not suffer significant modifications in its physicochemical properties.

Paulownia as a raw material for the production of pulp by soda–anthraquinone cooking with or without previous autohydrolysis

AbstractBACKGROUND: A central composite experimental design and multiple regression were used to model the production of pulp and paper sheets from a Paulownia fortunei × tormentosa × elongata trihybrid clone. Also, the same experiments were carried out with the solid phase after autohydrolysis of the raw material.RESULTS: The results were compared with those obtained from the solid phase remaining after autohydrolysis of the raw material with a view to optimizing the use of hemicelluloses and cellulose by fractionation. Pulp and paper sheets from the trihybrid clone surpass those from other Paulownia species such as P. fortunei and P. elongata in physical properties such as tensile index (11.6–49.1 Nm g−1), burst index (0.23–2.41 MPa m2 kg−1), tear index (0.71–3.03 mN m2 g−1) and intrinsic viscosity (427–958 cm3 g−1).CONCLUSIONS: The solid phase obtained by autohydrolysis of the Paulownia trihybrid provides pulp and paper sheets comparable in strength‐related properties with those of pulp directly produced from the raw material, but using substantially milder operating conditions and with the added advantage that the autohydrolysis treatment provides highly valorizable liquor. Copyright © 2011 Society of Chemical Industry

Editorial- Valorization of Agroforest Crops for Biomass Utilization

Editorial- Valorization of Agroforest Crops for Biomass Utilization

Manufacture of fibrous reinforcements for biodegradable biocomposites from Citysus scoparius

AbstractBACKGROUND: Cytisus scoparius samples were processed with hot, compressed water (autohydrolysis treatments) to obtain both fiber‐containing solids (suitable as reinforcements for composites) and a liquid phase containing sugar oligomers derived from hemicelluloses. The solid phase from autohydrolysis, mainly made up of cellulose and lignin, was employed for manufacturing polylactic acid (PLA)‐based biodegradable composites. The mechanical properties, water uptake and thermal properties of composites were assessed.RESULTS: The hydrolysis of the major hemicellulose polysaccharide components of Cytisus scoparius was interpreted using kinetic models based on sequential pseudo‐homogeneous first‐order, irreversible reactions. Operating under non‐isothermal conditions, the autohydrolysis experiment carried out at up to 215 °C led to the maximum concentration of sugar oligomers (accounting for about 71% of the initial xylan). These compounds can be employed for a variety of purposes, including applications as prebiotics. Composites containing autohydrolyzed fibers presented both improved impact strength and reduced water absorption ability.CONCLUSIONS: Autohydrolysis of Cytisus scoparius led to a liquid phase containing xylooligosacharides with commercial value, and to a solid phase suitable as a reinforcement for PLA‐based composites with reduced water retention ability. Copyright © 2010 Society of Chemical Industry

Effect of autohydrolysis and enzymatic treatment on oil palm (Elaeis guineensis Jacq.) frond fibres for xylose and xylooligosaccharides production

Oil palm (Elaeis guineensis Jacq.) is one of the most important commercial crops for the production of palm oil, which generates 10.88 tons of oil palm fronds per hectare of plantation as a by-product. In this study, oil palm frond fibres were subjected to an autohydrolysis treatment using an autoclave, operated at 121 °C for 20-80 min, to facilitate the separation of hemicelluloses. The hemicellulose-rich solution (autohydrolysate) was subjected to further hydrolysis with 4-16 U of mixed Trichoderma viride endo-(1,4)-β-xylanases (EC 3.2.1.8) per 100 mg of autohydrolysate. Autoclaving of palm fronds at 121°C for 60 min (a severity factor of 2.40) recovered 75% of the solid residue, containing 57.9% cellulose and 18% Klason lignin, and an autohydrolysate containing 14.94% hemicellulose, with a fractionation efficiency of 49.20%. Subsequent enzymatic hydrolysis of the autohydrolysate with 8 U of endoxylanase at 40 °C for 24 h produced a solution containing 17.5% xylooligosaccharides and 25.6% xylose. The results clearly indicate the potential utilization of oil palm frond, an abundantly available lignocellulosic biomass for the production of xylose and xylooligosaccharides which can serve as functional food ingredients.

Effect of autohydrolysis of Miscanthus x giganteus on lignin structure and organosolv delignification

The influence of the operating conditions of Miscanthus x Giganteus autohydrolysis on the composition of the solid residues and hydrolysates was examined. Milled wood lignin (MWL) extracted after autohydrolysis treatments performed at the same severity but at different temperatures were studied by (13)C and (31)P NMR in order to obtain a more complete picture of the changes in lignin structure occurring during the autohydrolysis. It was proposed that (1) the lignin homolytical fragmentation route should be enhanced with an increase of the temperature of the autohydrolysis treatment and (2) addition of a catalytic amount of 2-naphthol during the autohydrolysis step not only enhanced the dissolution of lignin but also allowed a better recovery of the hemicellulose sugars. A combined process involving an optimized autohydrolysis step (carried out in presence or not of 2-naphthol) and a low severity ethanol organosolv treatment was described for the separation and recovery of lignin, cellulose and hemicelluloses.

Integral valorization of tagasaste ( Chamaecytisus proliferus) under hydrothermal and pulp processing

Tagasaste wood ( Chamaecytisus proliferus L.F. ssp palmensis) was characterized, chemical and energy terms, and assessed its potential as a lignocellulosic raw material, and its integral fractionation by autohydrolysis and delignification with ethanol. The hydrothermal treatment of the raw material at 175–185 °C provided a liquor containing a substantially increased amount of oligomers (between 16.6% and 47.4% as percentages with respect to the content of the raw material in each polymer fraction). A cellulose pulp with autohydrolysis treatment increased yields (53–60%), reduced Kappa number (28.8–34.6) but also viscosity (755–857 mL/g), and decreased paper strength (2.97–5.22 kN m/kg). However, beating ethanol cellulose from tagasaste was found to improve its strength-related properties more markedly than in soda pulp from the same material (tensile index of 44 kN m/kg).

Study of the antioxidant capacity of Miscanthus sinensis lignins

The present work studied the antioxidant capacity of the lignin obtained from Miscanthus sinensis . As the lignin structure is very complex, extraction and separation processes highly influence obtained lignin structure and its properties, including the antioxidant activity. Lignin fractions were obtained from black liquor resulting from different fractionating and autohydrolysis processes of M. sinensis . Different lignin fractions with specific molecular weight were separated by ultrafiltration using different cut-off ceramic membranes (10 and 15 kDa). The physico-chemical properties, phenolic groups content and the antioxidant capacity of each lignin sample were studied. It was found that antiradical activity of the analyzed lignin samples was closely related with the used fractionating process (soda, organosolv and autohydrolysis treatments). The ultrafiltration process allows obtaining lignins with different antioxidant capacity, improving this property as the used cut-off was greater.