title: Removal of lipophilic extractives from paper pulp by laccase and lignin-derived phenols as natural mediators.
abstract: In this paper, we show for the first time that lignin-derived phenols can act as laccase mediators for the removal of lipophilic compounds from paper pulp. These natural mediators represent an alternative to synthetic mediators, such as 1-hydroxybenzotriazole (HBT), that cause some economic and environmental concerns. Unbleached kraft pulp from eucalypt wood, which contained free and conjugated sterols responsible for pitch deposition in the manufacture of totally chlorine free paper, was treated with a fungal laccase in the presence of syringaldehyde, acetosyringone, and p-coumaric acid as mediators. The composition of lipophilic extractives in the pulps after the enzymatic treatment followed by a hydrogen peroxide stage was analyzed by gas chromatography and gas chromatography/mass spectrometry. The enzymatic treatment using syringaldehyde as laccase mediator caused the highest removal (over 90%) of free and conjugated sitosterol, similar to that attained with HBT, followed by acetosyringone (over 60% removal), whereas p-coumaric acid was barely effective. Moreover, recalcitrant oxidized steroids surviving laccase-HBT treatment could be removed when using these natural mediators. Pulp brightness was also improved (from 57% to 66% ISO brightness) by the laccase treatment in the presence of the above phenols followed by the peroxide stage due to the simultaneous removal of lignin.
authors.affiliation: Instituto de Recursos Naturales y Agrobiología de Sevilla, CSIC, PO Box 1052, E-41080 Seville, Spain. anagu@irnase.csic.es
authors.forename: Ana
authors.initials: A
authors.lastname: Gutiérrez
authors.forename: Jorge
authors.initials: J
authors.lastname: Rencoret
authors.forename: David
authors.initials: D
authors.lastname: Ibarra
authors.forename: Setefilla
authors.initials: S
authors.lastname: Molina
authors.forename: Susana
authors.initials: S
authors.lastname: Camarero
authors.forename: Javier
authors.initials: J
authors.lastname: Romero
authors.forename: José C
authors.initials: JC
authors.lastname: Del Río
authors.forename: Angel T
authors.initials: AT
authors.lastname: Martínez
mesh_terms: D000098:Acetophenones / Q000737:chemistry; D001547:Benzaldehydes / Q000737:chemistry; D003373:Coumaric Acids / Q000737:chemistry; D005052:Eucalyptus / Q000737:chemistry; D007220:Industrial Waste; D042845:Laccase / Q000737:chemistry*; D008031:Lignin / Q000737:chemistry*; D010209:Paper; D010636:Phenols / Q000737:chemistry*; D010936:Plant Extracts / Q000737:chemistry / Q000302:isolation & purification; D011422:Propionates; D018505:Waste Management / Q000379:methods*; D014934:Wood / Q000737:chemistry
chemical_list: D000098:Acetophenones; D001547:Benzaldehydes; D003373:Coumaric Acids; D007220:Industrial Waste; D010636:Phenols; D010936:Plant Extracts; D011422:Propionates; C069665:syringaldehyde; C051667:acetosyringone; D008031:Lignin; D042845:Laccase; C495469:p-coumaric acid