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Biological delignification in paper manufacture

The project investigated the use of various biological treatments, based on either growing fungi or isolated enzymes, in the preparation of paper pulp from straw. Straw is made up of the cellulose components which form the bulk of the final paper, as well as hemicellulose (carbohydrate) and lignin (phenolic) materials which are removed and/or bleached during processing. Conventionally pulping uses alkali salts and may use strong chemical bleaches based on chlorine, which produces polluting effluents and environmental concern. The enzyme approach should provide less degraded by-product streams and reduced environmental impact. However, although many fungi produce enzymes which breakdown hemicellulose and some produce lignin degrading systems, considerable development and optimization is required to make such approaches commercially viable. Significant advances have been made in understanding the mechanisms and possibilities.

Methodologies were developed to study lignin modification by fungi and enzymes. The correlation analysis between laboratory and papermaking parameters, the selection of fungal strains, and the ultrastructural characterization of wheat straw tissues were among the initial results obtained. The identification and characterization of ligninolytic enzymes produced by fungi during lignin degradation under simultaneous saccharification/fermentation as well as optimization of enzyme production and purification together with the chemical and ultrastructural characterisation of wheat straw treated with fungi and the production of polyclonal antibodies used in immunolocalization were significant results. Evidence for enzymic modification of lignin in wheat straw cell was obtained using these techniques and new analytical methods were developed for absolute quantification of pyrolysis products and for laboratory evaluation of small samples, and used to show improved mechanical properties in straw pulp treated with enzyme 'cocktails' and mediators.

Reported by

Centro de Investigaciones Biologicas
Velazquez 144
28006 Madrid
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