Studies on Microbial and Enzymatic Applications in Paper and Pulp Manufacturing from Non-Woody Plants Based on White-Rot..., 2000 Pulping / Process & Product Quality Conference Proceedings

A. Martinez, S. Camarero, F. J. Ruiz-Duenas, A. Heinfling, M. J. Martinez--Wood biopulping has been investigated to save energy and improve pulp properties, but non-woody plants present more favorable conditions for biological delignification. Pleurotus strains were selected for wheat-straw biopulping decreasing refining energy, and the best results were obtained with Pleurotus eryngii. Straw treatment with this fungus resulted in low lignin content and individualization of sclerenchymatic fibers. By contrast, Phanerochaete chrysosporium strongly hydrolyzed polysaccharides and destroyed fibers. When mild alkaline cooking was combined with P. eryngii pretreatment, the mechanical properties were similar to those of semichemical pulps. Pleurotus eryngii does not produce lignin peroxidase (LiP) nor manganese peroxidase (MnP), but a versatile peroxidase combining catalytic properties of the above peroxidases. Their protein sequence shows higher identity with P. chrysosporium LiP than MnP, but the molecular structure includes a Mn-binding site. MnP from different fungi have been investigated for pulp manufacturing. The Pleurotus peroxidases have higher biotechnological interest because of broad substrate specificity. Using analytical pyrolysis we demonstrated their capability to attack lignin in wheat cell-wall causing a preferential removal of phenolic units. The new peroxidases were also able to decolorize azo and phthallocyane industrial dyes that cause environmental problems, and are not efficiently oxidized by LiP and MnP.