N. Rothschild et al., LIGNINOLYTIC SYSTEM FORMATION BY PHANEROCHAETE-CHRYSOSPORIUM IN AIR, Applied and environmental microbiology, 61(5), 1995, pp. 1833-1838
This study characterizes the effect of oxygen concentration on the syn
thesis of ligninolytic enzymes by Phanerochaete chrysosporium immobili
zed on polyurethane foam cubes in a nonimmersed liquid culture system
and maintained under different carbon-to-nitrogen (C/N) ratios and lev
els. Lignin peroxidase (LIP) activity was obtained in cultures exposed
to air when the C/N ratio was low (7.47), i.e., when nitrogen levels
were high (C/N = 56/45 mM) or carbon levels were low (C/N = 5.6/4.5 mM
). At the low C/N ratio, the fungus was carbon starved and did not pro
duce extracellular polysaccharides. At a high C/N ratio (153), i.e., u
nder conditions of excess carbon (nitrogen limitation) (C/N = 56/2.2 m
M), cultures exposed to air produced large amounts of polysaccharide,
and LIP activity was detected only in cultures exposed to pure oxygen.
Under high-nitrogen conditions, LTP production was 1,800 U/liter in c
ultures exposed to pure oxygen and 1,300 U/liter in cultures exposed t
o air, with H1 and H2 being the main isoenzymes. The oxygen level did
not significantly alter the isoenzyme profile, nor did low-carbon cond
itions. The formation of manganese peroxidase was generally less affec
ted by the oxygen level than that of LIP but tvas considerably reduced
by a low C/N ratio. The effects of oxygen level and C/N ratio on the
synthesis of glyoxal oxidase paralleled their effects on LIP synthesis
except in the case of high nitrogen, which totally suppressed glyoxal
oxidase activity.