Bleaching of kraft pulp with multi-stage biological treatments.

Tsuchikawa, Kimio; Kondo, Ryuichiro; Sakai, Kokki

doi:10.2524/jtappij.49.1332

Cited by 12 publications

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“…The highest brightness that has been achieved by fungal treatment is 80%, after a two-stage treatment of hardwood pulp with YK-624 (9). Usually the pulp brightness after fungal treatment is 50-60%, but it can be increased to 80-90% by post-treatment with chlorine dioxide (2) or peroxide (5,10).…”

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Enzymology of Kraft Pulp Bleaching by Trametes versicolor

Paice¹,

Archibald²,

Bourbonnais³

et al. 1996

ACS Symposium Series

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Trametes versicolor and other white-rot fungi can lower the residual lignin content (kappa number) and increase brightness of kraft pulps without diminishing the pulps' strength or yield. Experiments with 14 C--labelled lignin indicate that the residual lignin is solubilized but not extensively mineralized by T. versicolor. Laccase, manganese peroxidase (MnP) and cellobiose dehydrogenase (CDH) are produced by the fungus during bleaching, but based on molecular modelling studies, they are unable to freely access residual lignin in the kraft pulp fibre wall. Two isozymes of laccase were purified and compared: both enzymes required a mediator such as ABTS for pulp delignification, and under optimum conditions could produce up to 55% lignin removal. However, several lines of evidence indicate that MnP is the key enzyme required for fungal bleaching. CDH has several potential roles in delignification, including generation of complexing agents and Μn(II) for MnP.Kraft pulps are brown, and must be bleached to acquire the high and stable brightness desired in fine writing and printing papers. Bleaching is achieved by removing the residual lignin from the pulp. Traditionally this was done with Cl 2 , but the production of organochlorine by-products has made chlorine bleaching an unpopular technology. Alternative bleaching chemicals, such as oxygen, ozone, and peroxide, are being adopted, but they are more expensive, or more likely to damage the strength of the pulp, than chlorine was. Biological delignification with fungi and their enzymes is an alternative approach which has shown promise, but has not yet attracted as much development effort as have the bleaching chemicals. Fungal BleachingThe lignin-degrading fungi are called white rots because of their characteristic bleaching effect as they decay wood. The first attempt to bleach kraft pulps with these fungi was

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“…Japanese scientists have extensively screened for fungi that bleach kraft pulps; Nishida isolated an unidentified strain, called IZU-154, that delignifles and brightens kraft pulps under solid-state fermentation conditions (3)(4)(5)(6). Kondo has selected an isolate, YK-624, of Phanerochaete sordida which is also very effective (7)(8)(9).…”

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confidence: 99%