Paper pulp delignification using laccase and natural mediators

Abstract

Three plant phenols, namely acetosyringone, syringaldehyde and p-coumaric acid, were selected as laccase redox mediators to investigate the enzymatic delignification of paper pulp (obtained from kraft cooking of eucalypt wood) in combination with peroxide bleaching. The effects of these natural mediators were compared with those obtained using the synthetic mediator 1-hydroxybenzotriazole. p-Coumaric acid only caused minor increase of pulp brightness and did not lower its kappa number (a rough estimation of the lignin content), whereas, the use of acetosyringone or syringaldehyde as laccase mediators enabled over 15% increase of final brightness and a similar decrease of final kappa number. Pulp delignification by laccase in the presence of the two latter natural mediators was demonstrated by analytical pyrolysis, which does not suffer from interferences by other pulp constituents as kappa number does, showing a preferential removal of lignin marker compounds compared with carbohydrate markers (up to 25% decrease of the corresponding ratio). This technique also revealed a modification of the residual lignin composition in terms of phenylpropane units after the laccase-mediator treatment. The use of laccase in combination with natural mediators, widely available from plant materials and pulping liquors, represents a promising alternative for environmentally friendly delignification of paper pulp.

Enzymatic approaches in paper industry for pulp refining and biofilm control

“…This association is named laccase mediator system (LSM). In these socalled LMS, the mediator is first oxidized by the laccase and then diffuses into the cell wall, oxidizing lignin inaccessible to laccase (Cadena 2010;Camarero 2007;Riva 2006: Widsten andKandelbauer 2008).…”

Immobilisation of laccase on Eupergit supports and its application for the removal of endocrine disrupting chemicals in a packed-bed reactor

“…This enzyme was reported to be a potential catalyst for the biodegradation of recalcitrant compounds: dyes, aromatic hydrocarbons compounds, olive oil mill wastewater and pulp delignification (Camarero et al 2007;Yamak et al 2009). In recent years, several research groups have explored the ability of free fungal laccases to remove a wide range of hormones: genistein, estrone, 17b-estradiol, estriol, and 17a-ethinylestradiol (Auriol et al 2008;Nicotra et al 2004;Tamagawa et al 2006;Lloret et al 2010).…”

Extracellular Laccase Produced by an Edible Basidiomycetous Mushroom,Grifola frondosa: Purification and Characterization

“…18,19) In addition to physiological functions, due to their broad substrate specificity, laccases have the unique ability to oxidize a broad range of xenobiotic compounds, such as synthetic dyes, 20) pesticides, 21) and chlorinated phenolics. 22) Hence, they have attracted considerable interest for application in many fields of industrial and environmental processes, including paper pulping and bleaching, 23,24) textile dye bleaching, 25) bioremediation, 26) and effluent detoxification. 27) The potential applications of laccases in food processing have also received much attention.…”