Mt. Moreira et al., MANGANESE IS NOT REQUIRED FOR BIOBLEACHING OF OXYGEN-DELIGNIFIED KRAFT PULP BY THE WHITE-ROT FUNGUS BJERKANDERA SP STRAIN BOS55, Applied and environmental microbiology, 63(5), 1997, pp. 1749-1755
The white rot fungus Bjerkandera sp. strain BOS55 extensively delignif
ied and bleached oxygen-delignified eucalyptus kraft pulp handsheets.
Biologically mediated brightness gains of up to 14 ISO (International
Standards Organization units) were obtained, providing high final brig
htness values of up to 80% ISO, In nitrogen-limited cultures (2.2 mM N
), manganese (Mn) greatly improved manganese-dependent peroxidase (MnP
) production, However, the biobleaching was not affected by the Mn nut
rient regimen, ranging from 1,000 mu M added Mn to below the detection
limit of 0.26 mu M Mn in EDTA-extracted pulp medium, The lowest Mn co
ncentration tested was at least several orders of magnitude lower than
the K-m known for MnP, Consequently, it was concluded that Mn is not
required for biobleaching in Bjerkandera sp. strain BOS55, Nonetheless
, fast protein liquid chromatography profiles indicated that MnP was t
he predominant oxidative enzyme produced even under culture conditions
in the near absence of manganese, High nitrogen (22 mM N) and exogeno
us veratryl alcohol (2 mM) repressed biobleaching in Mn-deficient but
not in Mn-sufficient culture medium, No correlation was observed betwe
en the titers of extracellular peroxidases and the biobleaching. Howev
er, the decolorization rate of the polyaromatic dye Poly R-478 was mod
erately correlated to the biobleaching under a wide range of Mn and N
nutrient regimens.