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Comparing the efficiency of the laccase–NHA and laccase–HBT systems in eucalyptus pulp bleaching

Paper ID Volume ID Publish Year Pages File Format Full-Text
3985 202 2010 7 PDF Available
Title
Comparing the efficiency of the laccase–NHA and laccase–HBT systems in eucalyptus pulp bleaching
Abstract

Laccase–mediator systems have the disadvantage that the mediator is expensive and potentially toxic. In this work, we used N-hydroxyacetanilide (NHA) in combination with laccase for the first time to bleach eucalypt pulp and found it to be a very promising, advantageous alternative to 1-hydroxybenzotriazole (HBT) as mediator. Thus, NHA is efficiently oxidized by laccase to a radical that absorbs light at 350 nm. Also, NHA is a better substrate for laccase than is HBT. An innovative result is that the enzyme is inactivated to a similar extent by both mediators under the typical treatment conditions of the bleaching step (L). This adverse effect, however, is strongly reduced in the presence of pulp. Moreover, the laccase–NHA system is as efficient as the laccase–HBT system in reducing the kappa number of eucalyptus pulp. Using a xylanase pretreatment or unbleached pulp boosts kappa number reduction and bleaching with the laccase–mediator system. Based on the results of cyclic voltammetry tests, NHA has a slightly lower redox potential than HBT, which further supports use of the former; also, unlike HBT, NHA is oxidized in a reversible, pH-dependent manner. Interestingly, the laccase–NHA system provides more efficient bleaching of eucalyptus pulp at pH 5 than it does at pH 4.

Keywords
Biobleaching; Eucalypt; Hydroxybenzotriazole (HBT); Laccase; N-hydroxyacetanilide (NHA); TCF
First Page Preview
Comparing the efficiency of the laccase–NHA and laccase–HBT systems in eucalyptus pulp bleaching
Publisher
Database: Elsevier - ScienceDirect
Journal: Biochemical Engineering Journal - Volume 49, Issue 3, 15 May 2010, Pages 401–407
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering