Mt. Moreira et al., BIOBLEACHING OF OXYGEN DELIGNIFIED KRAFT PULP BY SEVERAL WHITE-ROT FUNGAL STRAINS, Journal of biotechnology, 53(2-3), 1997, pp. 237-251
Twenty-five white rot fungal strains were tested for their ability to
bleach Eucalyptus globulus oxygen delignified kraft pulp (OKP). Under
nitrogen-limited culture conditions, eight outstanding biobleaching st
rains were identified that increased the brightness of OKP by more tha
n 10 ISO units compared to pulp incubated in sterile control medium. T
he highest brightness gain of approximately 13 ISO units was obtained
with Bjerkandera sp. strain BOS55, providing a high final brightness o
f 82% ISO. This strain also caused the greatest level of delignificati
on, decreasing the kappa number of OKP by 29%. When the white rot fung
al strains were tested in nitrogen-sufficient medium, the extracellula
r activities of laccase and peroxidases increased in many strains; non
etheless, the pulp handsheets were either destroyed or brightness gain
s were lower than those obtained under nitrogen-limitation. The titer
of ligninolytic enzymes was not found to be indicative of biobleaching
potential. However, the best biobleaching strains were generally char
acterized by a predominance of manganese dependent peroxidase (MnP) ac
tivity compared to other ligninolytic enzymes and by a high decolorizi
ng activity towards the polyanthraquinone ligninolytic indicator dye,
Poly R-478. (C) 1997 Elsevier Science B.V.