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Appl. Environ. Microbiol., Jul 1995, 2476-2481, Vol 61, No. 7
J Tapia and R Vicuna
(sup14)C-synthetic lignin mineralization by the basidiomycete Ceriporiopsis
subvermispora occurs at the highest rate (about 30% after 29 days) in
liquid cultures containing 1% glucose and a growth-limiting amount (1 mM)
of ammonium tartrate. The titers of manganese peroxidase (MnP) and laccase
are lower in these cultures than in cultures containing 1% glucose and 10
mM ammonium tartrate, where the extent of lignin mineralization in the same
period is only about 15%. The inverse correlation between enzyme activity
and lignin mineralization is also observed when ammonium tartrate is
replaced by ammonium chloride or Casamino Acids as the source of nitrogen.
This phenomenon can be explained by a gradual increase in the pH of the
medium that takes place only in the cultures with high nitrogen
concentrations. Supporting this finding, when cultures with 1 mM ammonium
tartrate were grown at different pHs, (sup14)CO(inf2) evolved more rapidly
from those with pH values near the optimum for MnP activity. On the other
hand, (sup14)CO(inf2) evolution from cultures containing 1% glucose
supplemented with 1 mM ammonium tartrate plus 9 mM sodium tartrate was as
low as that from cultures with a high ammonium tartrate concentration.
Since the changes in the pH of these cultures were not as pronounced as
those in cultures containing high nitrogen concentrations, tartrate itself
may also be contributing to limit the extent of lignin mineralization.
Considering that pH instability seems to constitute a common feature of
fungal cultures, precautions must be taken to avoid underestimation of
their ligninolytic efficiencies.
Copyright © 1995, American Society for Microbiology
Synthetic Lignin Mineralization by Ceriporiopsis subvermispora Is Inhibited by an Increase in the pH of the Cultures Resulting from Fungal Growth
Laboratorio de Bioquimica, Facultad de Ciencias Biologicas, Pontificia Universidad Catolica de Chile, Casilla 114-D, Santiago, Chile
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