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J Ind Microbiol Biotechnol ; 28(4): 204-6, 2002 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-11986920


Cellulase-free xylan-degrading enzyme preparations from Acrophialophora nainiana, Humicola grisea var. thermoidea and two Trichoderma harzianum strains were used as bleaching agents for Eucalyptus kraft pulp, prior to a chlorine dioxide and alkaline bleaching sequence. In comparison to the control sequence (performed without xylanase pretreatment), the sequence incorporating enzyme treatment was more effective. Removal of residual lignin was indicated by a reduction in kappa number. Overall, enzyme preparations from T. harzianum were marginally more effective in reducing pulp viscosity and chlorine chemical consumption and improving the brightness of the kraft pulp. However, the highest reduction in pulp viscosity was mediated by the xylanase preparation from A. nainiana. Xylanase pretreatment compares very favorably with that of chemical pulping.

Fungos/enzimologia , Lignina/metabolismo , Xilosidases/isolamento & purificação , Eucalyptus/metabolismo , Xilano Endo-1,3-beta-Xilosidase , Xilosidases/metabolismo
Biotechnol Prog ; 16(3): 522-4, 2000.
Artigo em Inglês | MEDLINE | ID: mdl-10835259


Trichoderma harzianum strains T4 and T6, Acrophialophora nainiana, and Humicola grisea var. thermoidea were screened for their ability to produce carbohydrate-degrading enzyme activities in a medium containing banana plant residue as the carbon source. The best balance of enzyme activities was obtained from cultures of H. grisea var. thermoidea. Xylanase activity from crude extract of A. nainiana had a maximum activity at pH 5.5-7.0 and a temperature range of 50-55 degrees C. It was stable up to 55 degrees C at pH 7.0 for at least 2 h. The fungi were also able to produce xylanase and pectinase activities when grown on extractives as substrate.

Frutas/metabolismo , Glicosídeo Hidrolases/biossíntese , Fungos Mitospóricos/enzimologia , Meios de Cultura , Concentração de Íons de Hidrogênio , Especificidade por Substrato , Temperatura