Modo de ação de xilanases de Aspergillus sp 2M1 em sequencias de branqueamento de polpas de Eucalyptus grandis totalmente livres de cloro

AUTOR(ES)
DATA DE PUBLICAÇÃO

1999

RESUMO

Unbleached Eucalyptus grandis kraft pulps were submitted to TCF bleaching sequences (XOP - Xylanase/Oxygen/Peroxide and XZP -Xylanase/Ozone/Peroxide) using a non-commercial enzyme (Asperzyme 2M1) at the X stage. During the enzymatic treatment, the xylanase charge, inducted carbon source, incubation temperature and incubation time were changed. The pulp samples obtained after bleaching were characterized by conventional physico/chemical analyses of cellulose and pulp and by scanning and transmission electron microscopy (SEM and TEM respectively), atomic force microscopy (AFM), x-ray photoelectron spectroscopy (XPS), fourier transformed infrared (FTIR), near infrared (NIR) and carbon 13 solid state magnetic ressonance spectrometry with cross polarization and magic angle spinning (CP/MAS C -NMR). The effluents were collected and characterized by reducing sugar and soluble lignin contents. The results indicated a better performance of xylanase treated pulps than the control ones into all bleaching sequence studied, it has been observed a cooperative effect between a-glucuronidase and b-xylanase. The oxygen pre-delignified pulps showed a distinct behavior when compared with the non pre-delignified pulps, with increase on their bleachability. The enzyme action was also affected by the oxygen pre-delignification. The effect of xylanase treatment could be observed in the carbohydrate composition of pulps and in the profiles of reducing sugars and lignin contents of effluents too. The surface analyses showed that FTIR, NIR and XPS spectroscopies could be able to help in the characterization of pulps during TCF bleaching. The rnicroscopic techniques demonstrated that the morphologic study together with the chemical analyses could be very useful tools in the mode of action in enzymatic bleaching sequences. Finally, the application of PCA permitted an improvement in the utilization of spectroscopical data of FTIR and NIR and demonstrated that it is possible to differentiate cellulose bleached pulps by these techniques.

ASSUNTO(S)

celulose biotecnologia

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