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Pontevedra, Spain

Babot E.D.,Institute Recursos Naturales | Rico A.,Institute Recursos Naturales | Rencoret J.,Institute Recursos Naturales | Kalum L.,Novozymes AS | And 5 more authors.
Bioresource Technology | Year: 2011

The ability of two natural phenols to act as mediators of the recombinant Myceliophthora thermophila laccase (MtL) in eucalypt-pulp delignification was investigated. After alkaline peroxide extraction, the properties of the enzymatically-treated pulps improved with respect to the control. The pulp brightness increased (3.1 points) after the enzymatic treatment with MtL alone, but the highest improvements were obtained after the MtL treatment using syringaldehyde (4.7 points) and especially methyl syringate (8.3 points) as mediators. Likewise, a decrease in kappa number up to 2.7 points was obtained after the MtL-methyl syringate treatment, followed by decreases of 1.4 and 0.9 points after the treatments with MtL-syringaldehyde and MtL alone, respectively. On the other hand, removal of the main lipophilic extractives present in eucalypt pulp was observed after the above laccase-mediator treatments. Finally, the doses of both MtL and methyl syringate were reduced, and results compatible with industrial implementation were obtained. © 2011 Elsevier Ltd.

Monje P.G.,University of Santiago de Compostela | Gonzalez-Garcia S.,University of Santiago de Compostela | Moldes D.,Polytechnic University of Catalonia | Vidal T.,Polytechnic University of Catalonia | And 3 more authors.
Water Research | Year: 2010

The great amount of pollutants released from kraft pulp processes, mainly from cooking and bleaching stages, is one of the most relevant environmental problems in this type of industry. New bleaching sequences are being studied based on the use of oxidative enzymes from fungal cultures. In this study, the bleaching systems consisting of Laccase and different mediators such as 1-hydroxybenzotriazole, violuric acid, syringaldehyde and methyl syringate in the bleaching sequence of Eucalyptus globulus kraft pulp were applied. The main objective of this study is to evaluate the aerobic and anaerobic biodegradability and toxicity to Vibrium fischeri of generated L-stage and total bleaching sequence effluents. The highest levels of aerobic and anaerobic degradation of the generated effluents were achieved for treatments with laccase plus violuric acid, with 80% of aerobic degradation and 68% of anaerobic biodegradation. V. fischeri toxicity was remarkably reduced for all the effluents after aerobic degradation. © 2010 Elsevier Ltd. All rights reserved.

Vila C.,University of Vigo | Francisco J.L.,ENCE | Santos V.,University of Vigo | Parajo J.C.,University of Vigo
Holzforschung | Year: 2013

The effects of hydrothermal treatments of Eucalyptus globulus wood have been evaluated in terms of the solid yield and the composition of the treated wood. The contents of cellulose, xylan, and Klason lignin in treated solids were determined and interpreted by means of kinetic models. Particular attention was paid to the degree of polymerization (DP) lowering of cellulose caused by hydrothermal treatments, which was assessed by measurements of intrinsic viscosity. Copyright © by Walter de Gruyter • Berlin • Boston.

Corredoira E.,CSIC - National Institute of Agrobiological Sciences | Ballester A.,CSIC - National Institute of Agrobiological Sciences | Ibarra M.,ENCE | Vieitez A.M.,CSIC - National Institute of Agrobiological Sciences
Tree Physiology | Year: 2015

A reproducible procedure for induction of somatic embryogenesis (SE) from adult trees of Eucalyptus globulus Labill. and the hybrid E. saligna Smith × E. maidenii F. Muell. has been developed for the first time. Somatic embryos were obtained from both shoot apex and leaf explants of all three genotypes evaluated, although embryogenic frequencies were significantly influenced by the species/genotype, auxin and explant type. Picloram was more efficient for somatic embryo induction than naphthaleneacetic acid (NAA), with the highest frequency of induction being obtained in Murashige and Skoog medium containing 40 μM picloram and 40 mg l-1 gum Arabic, in which 64% of the shoot apex explants and 68.8% of the leaf explants yielded somatic embryos. The embryogenic response of the hybrid was higher than that of the E. globulus, especially when NAA was used. The cultures initiated on picloram-containing medium consisted of nodular embryogenic structures surrounded by a mucilaginous coating layer that emerged from a watery callus developed from the initial explants. Cotyledonary somatic embryos were differentiated after subculture of these nodular embryogenic structures on a medium lacking plant growth regulators. Histological analysis confirmed the bipolar organization of the somatic embryos, with shoot and root meristems and closed procambial tissue that bifurcated into small cotyledons. The root pole was more differentiated than the shoot pole, which appeared to be formed by a few meristematic layers. Maintenance of the embryogenic lines by secondary SE was attained by subculturing individual cotyledonary embryos or small clusters of globular and torpedo embryos on medium with 16.11 μM NAA at 4-to 5-week intervals. Somatic embryos converted into plantlets after being transferred to liquid germination medium although plant regeneration remained poor. © The Author 2015. Published by Oxford University Press. All rights reserved.

Vila C.,University of Vigo | Romero J.,ENCE | Francisco J.L.,ENCE | Santos V.,University of Vigo | Paraji J.C.,University of Vigo
BioResources | Year: 2012

To assess the feasibility of implementing hemicellulose recovery stages in kraft mills, Eucalyptus globulus wood samples were subjected to aqueous treatments with hot, compressed water (autohydrolysis processing) to achieve partial dissolution of xylan. Autohydrolyzed solids were subjected to kraft pulping under selected conditions to yield a pulp of low kappa number, and to an optimized TCF bleaching sequence made up of three stages (alkaline oxygen delignification, chelating, and pressurized hydrogen peroxide), with minimized additions of pulping and bleaching chemicals. The final product had a relatively low kappa number (1.4), 641 mL/g ISO intrinsic viscosity, and 86.4% brightness.

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