| Abstrakt: |
Ligninolytic enzymes from basidiomycete fungi are of special interest in the pulp and paper industry for delignification processes, since they promote depolymerization of lignin in cellulosic pulps by oxidation. Among these enzymes are laccases, which oxidative power is favored by chemical or natural mediators. In this research, a ligninolytic enzyme extract, obtained from Pleurotus ostreatus was applied along with ABTS as a chemical mediator, to delignify toquilla straw (Carludovica palmata) pulp. The enzyme extract was obtained from fermentation of a nutrient medium in polyurethane support. Enzymatic activity was analyzed in the extract, while laccases were assessed through electrophoresis. Extract dosages were of 3.5, 5, 10 and 20 U/g pulp along with 1 mM ABTS. Delignification conditions were 45 °C, pH 4.5 and 200 rpm for 120 h. Ligninolytic enzyme activity was between 861.57 and 1350.69 U/L, and molecular sizes ranged from 66 to 97 kDa. According to a surface response analysis, 14 U/g pulp of enzyme extract and 1 mM ABTS reached maximum delignification, with a final lignin content of 5.04%. The enzyme – mediator system (EMS) caused negative effects on pulp coloration, which was rectified through a subsequent bleaching phase. Finally, the explosion resistance was 15% higher in paper made from EMS pulp, in comparison to the control treatment. Other properties such as the resistance to air flow and width did not present significant differences. The application of enzymatic extracts and a chemical mediator turned out to be an alternative to delignify toquilla straw pulp. [ABSTRACT FROM AUTHOR] |
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