Eucalyptus Globulus Wood Chips Research Articles

Purification of Eucalyptus globulus steam explosion hydrolysates via nanofiltration to recover xylooligosaccharides

Nanofiltration was applied to purify steam explosion hydrolysates obtained from Eucalyptus globulus woodchips. The complex hydrolysate comprised xylooligosaccharides, monosaccharides, glucuronic acid (GluA), and degradation products, including acetic acid, furfural, and 5-hydroxymethylfurfural (HMF). Membranes with 750 and 200 Da molecular weight cut-offs were assessed for their ability to retain oligosaccharides while allowing degradation products to permeate. Using the 750 Da membrane, the average compound retention order was: acetic acid (9.8 %) < furfural (10.8 %) < HMF (31.4 %) ≪ arabinose (52.5 %) < xylose (63.8 %) < glucose (76.0 %) < GluA (90.6 %). The separation mechanism for neutral saccharides and furans was primarily molecular sieving, while Donnan exclusion was the primary retention mechanism responsible for GluA. Separation factors obtained for acetic acid and furfural over xylotriose and xylobiose exceeded 10 and 3, respectively, for both membranes, showing that desired compounds were predominantly retained. Permeability loss during nanofiltration was fully restored after implementing cleaning-in-place for both membranes.

Effect of lignin on the morphology and rheological properties of nanofibrillated cellulose produced from γ-valerolactone/water fractionation process

The influence of lignin content on nanocellulosic fibril morphology, charge, colloidal stability and immobilization has been systematically investigated employing a series of nanofibrillated cellulose (NFC) with varying residual lignin content and compared to those of NFC made from fully bleached pulp. The lignin-containing pulps were obtained from the fractionation of Eucalyptus globulus wood chips in gamma-valerolactone (GVL)/water under the same conditions, they differ by the intensity of washing for lignin removal. The reference pulp originated from another cook of eucalyptus wood chips, and was fully bleached with a short Elemental-Chlorine-Free (ECF) sequence. All the pulps have a comparable hemicellulose-to-cellulose ratio and CED viscosity. NFC suspensions of 1 wt% concentration were mechanically produced from fluidization. The results indicated that the fibrils morphology, thickness and corresponding flocculation within NFC suspensions was highly influenced by the presence of lignin unevenly distributed on the fibril surface and within the suspension as particles. The presence of lignin in NFC suspension had a large impact on the rheology and dewatering of the NFC. Samples with high lignin content had distinguishable viscoelastic properties due to the greater flocculation of thicker fibrils and lower gel-like characteristics, with better dewatering properties.

Towards the improvement of Eucalyptus globulus chemical and mechanical pulping using endophytic fungi

Five endophytic fungal strains isolated from Eucalyptus sp. and capable of producing laccase (Neofusicoccum luteum, Ulocladium sp., Pringsheimia smilacis, Hormonema sp., and Neofusicoccum australe) were used to pre-treat Eucalyptus globulus wood chips. After the fungal pre-treatment, chips were submitted to kraft or mechanical pulping.All the endophytic fungal strains provided higher delignification during kraft pulping than control sample. The highest increase was achieved by Hormonema sp. (26.7%), which also reduced the NaOH consumption by 11.6% and increased mechanical strength (increases in tensile, tear and burst indices of 28.4%, 15.6% and 43.9%, respectively).Regarding mechanical pulping, only N. australe was able to reduce the energy consumed during the process (8.4%). However, all pulps from fungal pre-treated chips showed higher refining degree and mechanical properties than the control pulp, which would probably allow a lower consumption of energy during mechanical pulping to achieve a specific refining degree. The best mechanical properties and the lowest kappa number were also found when Hormonema sp. was applied.

Can Acceptable Pulp be Obtained from Eucalyptus globulus Wood Chips after Hemicellulose Extraction?

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

Manufacture of Microcrystalline Cellulose from Eucalyptus globulus Wood Using an Environmentally Friendly Biorefinery Method

In this work, hemiceluloses and lignin were solubilized by successive steps of autohydrolysis and delignification, and the resulting solids were processed to obtain microcrystalline cellulose. Eucalyptus globulus wood chips were treated with hot, compressed water under selected conditions to cause the hydrolytic breakdown of heteroxylan into substituted saccharides. The xylan-depleted solids were treated with acetic acid under optimized conditions to remove lignin, leaving a solid phase with high cellulose content. This latter was subjected to Totally Chlorine Free (TCF) bleaching to yield microcrystalline cellulose. These sequence autohydrolysis-organosolv delignification-TCF bleaching enabled the selective separation of hemicelluloses (which were mainly converted into soluble saccharides), lignin (as compounds soluble into acetic acid), and microcrystalline cellulose, according to an environmentally friendly biorefinery method.

Optimal Pretreatment of Eucalyptus globulus by Hydrothermolysis and Alkaline Extraction for Microbial Production of Ethanol and Xylitol

Fractionation of Eucalyptus globulus wood chips is mandatory for developing a biorefinery process. In order to achieve this, products released from hydrothermolysis pretreatment were studied within the severity (log R0) range 3.3–4.5. The highest solubilized xylose yield was 56% (DWB) at log R0 3.9. Values higher than log R0 4.1 have led to high xylose dehydration rates. Detoxification steps applied to the liquor removed acetic acid (55%), furfural (94%), and hydroxymethylfurfural (HMF) (31%). Fermentation of liquor with Candida guilliermondii resulted in a xylitol yield of 0.37 g of xylitol produced per gram of xylose consumed (equivalent to 71% of the control with pure xylose). Pulp-1 (from hydrothermolysis pretreatment) was further pretreated with NaOH for lignin removal (obtaining Pulp-2). Cellulose composition in Pulp-1 and Pulp-2 remains almost unaltered; lignin content in Pulp-2 was 50% lower than in Pulp-1. Simultaneous saccharification and fermentation (SSF) experiments for both pulps reached similar ethanol yields of 0.76 and 0.70 g of ethanol produced per gram of ethanol potentially produced from wood, respectively. Recovery of hemicellulose at the beginning of the process is a key step for getting pulps with high cellulose composition available for developing a biorefinery process of E. globulus.

Biorefinery in a pulp mill: simultaneous production of cellulosic fibers from Eucalyptus globulus by soda-anthraquinone cooking and surface-active agents

Abstract Industrial Eucalyptus globulus wood chips were submitted to different autohydrolysis conditions followed by kraft cooking and soda-anthraquinone cooking. The autohydrolyzed wood chips were much easier to delignify than the control wood chips. Soda-anthraquinone cooking could be performed at a cooking temperature that was 20°C lower than that for the kraft cooking on control wood chips. Furthermore, the active alkali could be reduced. The resulting unbleached pulps reacted as well to oxygen delignification as the control pulps and could be further bleached to 90% ISO brightness with a D(EP)D sequence. The autohydrolysis liquors were investigated for their suitability as a source for the synthesis of alkylpolyxylosides (APX). These surface-active agents are synthesized through the reaction between the saccharides of the autohydrolysates and a fatty alcohol, with the former being the hydrophilic and the latter being the hydrophobic part of the molecule. The impact of the substances detected in autohydrolysates on the APX synthesis was studied. It was demonstrated that lignin dissolved during autohydrolysis should at least partially be removed before the production of APX.

Kraft pulping and ECF bleaching of Eucalyptus globulus pretreated by the white-rot fungus Ceriporiopsis subvermispora

Eucalyptus globulus wood chips were decayed by the lignin-degrading fungus Ceriporiopsis subvermispora as a pretreatment step before kraft pulping. Weight and component losses of wood after the biotreatment were the following: weight (5%), glucans (1.5%), xylans (4.3%), lignin (5.7%) and extractives (57.5%). The residual amount of lignin (expressed by the kappa number) in pulps from biotreated wood chips was lower than that of pulps from the undecayed control. Depending on the delignification degree, kraft biopulps presented similar or up to 4% increase in pulp yield and 20% less hexenuronic acids (HexA) than control pulps. The extended delignification with O2 decreases approximately 50% of the kappa number of the pulps and increases brightness, but had no effect in HexA reduction. The bleaching steps with chlorine dioxide (D0ED1 sequence) decreased the kappa number up to 97%, increased pulp brightness up to 84% ISO and decreased HexA amount up to 91%. The use of C. subvermispora in biopulping of E. globulus generated important benefits during the production of kraft pulps that are reflected in a high pulp yield, low residual lignin content, low HexA amount, high brightness and viscosity of the biopulps as compared with pulps produced from untreated wood chips.

Steam explosion and enzymatic pre-treatments as an approach to improve the enzymatic hydrolysis of Eucalyptus globulus

Abstract Eucalyptus globulus woodchips were subjected to steam explosion under a variety of operational conditions in order to evaluate their effect on a subsequent enzymatic hydrolysis. Steam explosion enhanced the enzymatic hydrolysis of the solid fraction. The application of a laccase-mediator system (LMS) before the enzymatic hydrolysis increased the glucose yield from 24.7 to 27.1%, probably as a result of the detoxification of the substrate. However, when xylanase was used to boost the LMS treatment, the hydrolysis rates did not improve. In order to assess the total amount of sugars obtainable from E. globulus , the liquid fraction obtained from the steam explosion was subjected to hydrolysis too. The enzymatic hydrolysis of the liquid fraction was more efficient than the acid hydrolysis, breaking down 82.7% of the xylooligosaccharide backbone into its monomeric constituent, xylose. The overall yield was 210 g of sugars per kg of raw material.

Sulfur-free dissolving pulps and their application for viscose and lyocell

In this study, the concept of multifunctional alkaline pulping has been approved to produce high-purity and high-yield dissolving pulps. The selective removal of hemicelluloses was achieved by either water autohydrolysis (PH) or alkaline extraction (E) both applied as pre-treatments prior to cooking. Alternatively, hemicelluloses were isolated after oxygen delignification in a process step denoted as cold caustic extraction (CCE). Eucalyptus globulus wood chips were used as the raw material for kraft and soda-AQ pulping. In all process modifications sulfur was successfully replaced by anthraquinone. By these modifications purified dissolving pulps were subjected to TCF bleaching and comprehensive viscose and lyocell application tests. All pulps met the specifications for dissolving pulps. Further more, CCE-pulps showed a significantly higher yield after final bleaching. Morphological changes such as ultrastructure of the preserved outer cell wall layers, specific surface area and lateral fibril aggregate dimension correlated with the reduced reactivity towards regular viscose processing. The residual xylan after alkali purification depicted a lower content of functional groups and a higher molecular weight and was obviously entrapped in the cellulose fibril aggregates which render the hemicelluloses more resistant to steeping in the standard viscose process. Simultaneously, the supramolecular structure of the cellulose is partly converted from cellulose I to cellulose II by the alkaline purification step which did not influence the pulps reactivity significantly. Nevertheless, these differences in pulp parameters did not affect the lyocell process due to the outstanding solubility of the pulps in NMMO. Laboratory spinning revealed good fiber strength for both, regular viscose and lyocell fibers. The high molecular weight xylan of the CCE-treated pulps even took part in fiber forming.

Evaluation of the white-rot fungi Ganoderma australe and Ceriporiopsis subvermispora in biotechnological applications

Ganoderma australe is a white-rot fungus that causes a selective wood biodelignification in some hardwoods found in the Chilean rainforest. Ceriporiopsis subvermispora is also a lignin-degrading fungus used in several biopulping studies. The enzymatic system responsible for lignin degradation in wood can also be used to degrade recalcitrant organic pollutants in liquid effluents. In this work, two strains of G. australe and one strain of C. subvermipora were comparatively evaluated in the biodegradation of ABTS and the dye Poly R-478 in liquid medium, and in the pretreatment of Eucalyptus globulus wood chips for further kraft biopulping. Laccase was detected in liquid and wood cultures with G. australe. Ceriporiopsis subvermispora produce laccase and manganese peroxidase when grown in liquid medium and only manganese peroxidase was detected during wood decay. ABTS was totally depleted by all strains after 8 days of incubation while Poly R-478 was degraded up to 40% with G. australe strains and up to 62% by C. subvermispora after 22 days of incubation. Eucalyptus globulus wood chips decayed for 15 days presented 1-6% of lignin loss and less than 2% of glucan loss. Kraft pulps with kappa number 15 were produced from biotreated wood chips with 2% less active alkali, with up to 3% increase in pulp yield and up to 20% less hexenuronic acids than pulps from undecayed control. Results showed that G. australe strains evaluated were not as efficient as C. subvermispora for dye and wood biodegradation, but could be used as a feasible alternative in biotechnological processes such as bioremediation and biopulping.

Enzymes produced by Ganoderma australe growing on wood and in submerged cultures

Enzymes produced by Ganoderma australe in solid-state fermentation and submerged cultures were evaluated. Strain A464 produced laccase activity in liquid medium and in solid-state cultures containing Drimys winteri or Eucalyptus globulus wood chips, while MnP and LiP activities were not detected. On the other hand, strain A272 cultured for 75 days on E. globulus presented MnP activity of 719 IU/kg of wood. The suitability of D. winteri wood as a substrate enabling MnP production was checked with a well-documented MnP-producing basidiomycete, Ceriporiopsis subvermispora, which produced MnP activity of 327 IU/kg of wood in 9-day-old cultures. Data from two different G. australe strains (A272 and A464) indicated that MnP secretion depended on strain origin as well as on culture conditions.

TCF bleaching of hardwood pulps obtained in organic acid media: Production of viscose-grade pulps

High-purity, viscose-grade pulps have been produced by means of delignification (in media containing formic or acetic acid) and TCF bleaching (using a E(O)ZP sequence). Aspen or Eucalyptus globuluswood chips were treated in media made up of either acetic acid, water and HCl or formic acid, water and hydrogen peroxide (Acetosolv and Milox technologies). Under selected conditions, unbleached pulps with kappa numbers in the range 14.0–28.5 were obtained at 50.0–53.7% pulp yield. These samples were subjected to E(O)ZP bleaching to reach the viscose-grade target values for chemical and physicochemical properties. Among the pulps tested, the bleached Milox pulp from Eucalyptus wood showed the best properties to be used for viscose manufacture (pentosan content of 1.4%, SCAN viscosity of 598 mL/g, ISO brightness of 89.9% and alkaline resistances of 90.1% and 97.0% in the R-10 and R-18 tests).