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The specific growth rate of suspended P. chrysosporium fungus in
batch culture was 0.176-0.186d-1，which was much lower than that
of mixed cultures in activated sludge system as well as that of
most aerobic bacteria. The inhibitory effects of PAHs on the
cell growth were always less with a PAH-acclimating fungus.
However, acclimating P. chrysosporium became inadaptability to
PAH loadings when the fungus was exposed in PAH-free influent
for a significant period. The optimum pH and tempera- ture for
the cell growth of P. chrysosporium was around pH 4.5 and at
37℃, and the activity-reversible range of pH was between
2.5-9.0 for the fungus. The compressive stress of immobilization
alginate-0.2g PAC capsule incorporating 2% (w/v) powdered
activated carbon (PAC) was 1.72 kg/cm2 in response to 50%
deformation of the capsule. The strength was much higher than
calcium alginate gel in which only 1.00 kg/cm2 was detected.
Moreover, in the same proportion of carbon in gel, the strength
of alginate-GAC (granular activated carbon) capsule was higher
than that of alginate-PAC bead. The capsule covered with fungal
mycelia could result in 20% increase in compression strength.
In this study, most of target PAHs could be removed from the
biotreatment system by white rot fungus P. chrysosporium. During
the treatment in batch system, the average removal of
naphthalene (NTL), fluoranthene (FLA) and benzo(a)pyrene (B(a)P)
by the suspended white-rot fungus was 0.04, 0.039and 0.038 mg/g-
cell on the basis of dried-cell weight, respectively. The
increase of biocapsule concentration in the bioreactor up to
12.88 g/L could enhance the removal of PAH. It was evidenced
that adsorption of PAHs to the biocapsules predominated the
initial removal of PAHs from the immobilization biotreatment
system during operation, and the biodegradation efficiency
gradually increased afterwards. The adsorption of target PAHs in
equilibrium condition by alginate-PAC capsules was a Freundlich
isotherm kinetic model in which the experimental constant k and
n was 0.021-0.045 and 3.69-5.65, respectively. The more of
benzene ring in PAHs the more of adsorption to the
immobilization capsules was obtained. However, PAHs adsorption
to alginate-PAC capsule was dramatic decreas- ed when the
capsule surface was covered by fungal mycelia completedly.
Freundlich isotherm constant of k and n was shifted to 0.0033
and 3.815, respectively, for PAHs adsorption on alginate-PAC-
cell capsules. Some unidentified metabolites were isolated by
HPLC when benzo(a)pyrene and fluoranthene were degraded by
suspended P. chrysosporium. Catechol was identified to be one of
the metabolites of naphthalene oxidation by the white-rot
fungus. According to the results of this experiment, and
referring to literatures issued for fungal metabolism of PAHs,
this report suggested that the target PAHs degraded by white rot
fungus P. chrysosporium might be converted to epoxide compounds
initially, which then underwent hydroxylation of the ring to
form hydroxydiol groups, and subsequent oxida- tion to quinones
or other diverse compounds in soluble form.
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