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Garcia-Fuentevilla L.L.,Institute Investigacion y Tecnologia Agraria y Agroalimentaria INIA | Martin-Sampedro R.,Institute Investigacion y Tecnologia Agraria y Agroalimentaria INIA | Carbajo J.M.,Institute Investigacion y Tecnologia Agraria y Agroalimentaria INIA | Diaz M.J.,University of Huelva | Eugenio M.E.,Institute Investigacion y Tecnologia Agraria y Agroalimentaria INIA
BioResources | Year: 2015

A TCF bleaching sequence consisting of a urea pretreatment stage (U), laccase-mediator system stage (L), alkaline extraction stage (E), and hydrogen peroxide bleaching stage (P) was used to study the effect of five independent variables on the dependent variables pulp properties, hydrogen peroxide consumption, and residual enzyme activity. Results showed that the most influential variable was L stage pulp consistency, followed by mediator and laccase dosages. On the other hand, oxygen pressure did not have a significant effect. The optimal UL partial sequence significantly enhanced the EP bleaching sequence: 49.8% vs. 33.4% delignification, up to 65.6% ISO vs. 56.3% ISO bleached brightness, and 50.3% vs. 89.9% peroxide consumption in the P stage. The ULE partial sequence also improved an ECF bleaching sequence (ULED0E1D1): 0.6 vs. 1.0 final kappa number; 82.7% ISO vs. 76.0% ISO brightness; and 54.1 N·m·g-1 vs. 51.9 N·m·g-1 and 3.3 KPa·m2·g-1 vs. 2.7 KPa·m2·g-1, tensile and burst indexes, respectively, when compared to the control D0E1D1 sequence. Source


Eugenio M.E.,Institute Investigacion y Tecnologia Agraria y Agroalimentaria INIA | Hernandez M.,University of Alcala | Moya R.,University of Alcala | Martin-Sampedro R.,Institute Investigacion y Tecnologia Agraria y Agroalimentaria INIA | And 2 more authors.
BioResources | Year: 2011

The aim of this work is to prove the suitability of a new alkaline and halotolerant bacterial laccase (SilA) produced by Streptomyces ipomoea CECT 3341 to enhance the conventional chemical bleaching process of an industrial eucalyptus kraft pulp. The laccase used for this study was a recombinant laccase obtained from cultures of E. coli BL21 (DE3) grown in LB liquid medium. The biobleaching experiment was carried out on Eucalyptus globulus kraft pulps using the above mentioned laccase and acetosyringone as natural mediator. Then, an alkaline extraction and further hydrogen peroxide steps were applied to evaluate the efficiency of the laccase-mediator system as a pretreatment in the bleaching sequences. Biobleached pulps showed a kappa number decrease and a brightness increase without decreasing the viscosity values significantly. Also, a reduction in the consumption of hydrogen peroxide was observed when the enzymatic treatment was applied to the pulp. CIE L*a*b* and CIE L*C* color coordinates measured in pulps demonstrated that among all treatments applied to pulps, the laccase-acetosyringone system presented the best optical properties even after an accelerated ageing process. Finally, it is also remarkable that during this treatment 64% of the laccase activity remained unaltered. Source

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