Environmental Engineering Reference
In-Depth Information
the latter to be the most efficient PAH degrader, with the ability to possibly
grow on fluoranthene (FLA).
With these previous studies as a basis, other fluoranthene degraders
were isolated and evaluated with respect to their taxonomic and metabolic
characteristics. Little is known concerning the bacterial genera that may be
responsible for microbial degradation of HMW PAHs in PAH-contaminated
sites; however, the results reported here suggest that
Sphingomonas
sp. are
commonly isolated from PAH-contaminated soils and their metabolic diver-
sity may vary considerably (Kim et al., 1996). Therefore, our efforts focused
on sphingomonads and on
S. paucimobilis
, in particular.
7.1.3.5.2 Cometabolism to enhance metabolic capabilities.
The comet-
abolic capabilities of
S. paucimobilis
strain EPA 505 are shown in Table 7.4
and Figure 7.4. After a 28-day incubation of a PAH mixture with EPA 505
and a chemical surfactant, there was considerable reduction in the
higher-molecular-weight PAHs.
Ye et al. (1996), using resting cell suspensions of EPA 505 and individual
PAHs, in place of a mixture, showed a similar pattern of degradation of
HMW PAHs, but to a greater extent. This is shown in Figure 7.4. Error bars
for the standard deviation of triplicates are not shown in this figure, but the
error was approximately 10%. The PAHs in this experiment were not growth
substrates for EPA 505.
This cometabolic capability is not typical of all PAH-degrading strains
studied. Table 7.4 shows the effectiveness of several isolates in their ability
to degrade different PAH fractions of creosote. The CRE strains were isolated
for their ability to grow on phenanthrene, the UNP/NP strains for their
ability to grow on fluoranthene, and the PYR1 strain for its ability to grow
Table 7.4
Amount of PAHs Remaining Following Biodegradation of PAH
Fractions by Selected Strains of PAH Degraders
Isolate/
Strain
Two-Ring
PAHs
Three-Ring
PAHs
Four-, Five-, and
Six-Ring PAHs
Total
PAHs
Initial
149.5 (0)
d
168.1 (0)
60.0 (0)
377.6 (NA)
Uninoculated
71.3 (NA)
107.0 (NA)
55.9 (NA)
234.1 (NA)
CRE 7
a
1.7 (98)
14.8 (86)
47.2 (16)
63.7 (73)
N3P2
b
0.5 (99)
4.9 (95)
46.1 (18)
51.5 (78)
UN1P1
b
0.5 (99)
3.4 (97)
43.0 (23)
46.9 (80)
EPA 505
b
0.3 (100)
2.2 (98)
18.6 (67)
21.1 (91)
PRY-1
c
4.8 (93)
70.6 (34)
40.3 (28)
115.7 (51)
a
Phenanthrene degrader.
b
Fluoranthene degraders.
c
Pyrene cometabolizer.
d
Numbers in parentheses indicate percent removed versus the uninoculated control.
Source:
Modified from J. Mueller et al., 1997. Antonie Leeuwenhoek 71, 329-343.
