Xilanases de aspergillus SP 2M1 : produção, caracterização e aplicação no branqueamento de polpas kraft

AUTOR(ES)
DATA DE PUBLICAÇÃO

1995

RESUMO

This study deals with the optimization for Aspergillus sp 2M1 growth and its xylanase production. Besides these aspects, some of lhe xylanase properties looking for an application in a bleaching Eucalyptus Kraft pulp were also studied. The optimal fungal growth conditions and enzyme production, in solid as in liquid media were following: Birchwood xylan as carbon source, temperature between 28-34°C, pH 6,0 and 150 rpm in the case of liquid cultures. No cellulase and very low b-xylosidase activities were found. The xylanase exhibited the maxima activity at pH 6,0 and temperature of 60°C, using Eucalyptus xylan as carbon source. The thermal stability of this enzyme underwent a large reduction with temperature increase, going from the average value of 14 hat 40°C to 10 min at 55°C. Through chemical reactions with specific inhibitors the carboxilic group appeared as the important group at the active center of the xylanase from Aspergillus sp 2M1. The kinetics study gave a first order reaction with a slope value equal to one and the inactivation due to 1-ethyl-3.(3-aminopropyl)carbodiimide was abolished in the xylotriose presence. The xylanase from Aspergillus sp 2M1 (Aperzyme 2M1) was applied in two different bleaching sequences: (xylanase)-Acid-Ozone-Chelant-Peroxide [(XAZQP)] and (xylanase)- Oxygen-Peroxide [(XOP)]. ln the first sequence the results with the utilization of the Asperzyme were similar to those in the control experiment, however, exhibiting a viscosity protection in the final fiber. The pulp physicomechemical properties appeared superior in the assays in which the enzyme was used. In the XOP sequence, in which Asperzyme was used, the results with two commercial xylanases as Cartazyme and Pulpzyme were compared. Asperzyme presented better results than Pulpzyme and similar to Cartazyme, protecting the viscosity and reducing the kappa number related to the control experiment. The efluent produced in the ozone sequence (XA ZQP) were analyzed following the color, residual lignin, total phenols,reductant sugars and toxicity (MICROTOX) and after fungal treatment with Lentinus edodes UEC 2021 strain during five days. The effluent obtained either in the presence or absence of xylanase were extremely toxic, but after fungal treatment the toxicity was totally eliminated. Then, Asperzyme 2M1 appeared as a potencial one for industrial pulp bleaching.

ASSUNTO(S)

madeira - quimica aspergilos enzinas de fungos xilanases

ACESSO AO ARTIGO

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