tailieunhanh - Dechlorination of bleached kraft pulp by laccase enzyme produced from some white rot fungi

The addition of a laccase inducer, xylidine, into the culture medium of T. versicolor led to an increase in dechlorination activity. In the experiment performed to find out the role of laccase activity in dechlorination reactions, a considerable reduction in the dissolved oxygen concentration due to laccase-dependent dechlorination activity was observed. | Turk J Biol 25 (2001) 67-72 © T†BÜTAK Dechlorination of Bleached Kraft Pulp by Laccase Enzyme Produced from Some White-Rot Fungi Arzu (TAÞPINAR) †NAL, Nazif KOLANKAYA Hacettepe University, Science Faculty, Department of Biology, Division of Biotechnology, 06532, Beytepe, Ankara-TURKEY Received: Abstract : The possibility of using crude laccase in the dechlorination of chlorine-based bleached kraft pulp was investigated. Culture supernatants of seven white-rot fungal strains and kraft-pulp samples taken from E1 (Alkaline Extraction-1), E2 (Alkaline Extraction-2) and D2 (Chlorinedioxide treatment) stages of chlorine-based bleaching processes were used as the laccase source and substrates respectively during the studies. The dechlorination activity of Trametes versicolor was found to be more than that of the other fungi examined. The addition of a laccase inducer, xylidine, into the culture medium of T. versicolor led to an increase in dechlorination activity. In the experiment performed to find out the role of laccase activity in dechlorination reactions, a considerable reduction in the dissolved oxygen concentration due to laccase-dependent dechlorination activity was observed. Stepwise enzyme treatment was found to be necessary for increasing the yield of dechlorination. Key Words: Biodechlorination, Kraft pulp, Laccase, Trametes (Coriolus) versicolor. Introduction The cooking and subsequent alkaline extractions are the main operational processes used in the production of kraft pulp from woody and other plant materials. During the application of the processes lignin bound to cellulose fibers is removed due to its high solubility in hot alkaline solution. However, lignin residues remain on the cellulose fibers and are responsible for the characteristic brownish colour of the kraft pulp. Bleaching of kraft pulp, which is necessary for the production of white paper products, is based on the removal of residual lignin from cellulose fibers. Since it has