Environmental Engineering Reference
In-Depth Information
25000
Strain FLA 10-2
Strain FLA 10-1
Strain FLA 9-1
Strain EPA 505
20000
15000
10000
5000
0
0
2
4
6
8
10
12
Days
Figure 7.7
Effect of 0.48 m
M
Triton X-100 on the mineralization of radiolabeled FLA
in minimal medium by four different fluoranthene degraders. (From Willumsen, P.A.
et al.,
Appl. Microbiol. Biotechnol
., 50: 475-483.)
strain EPA 505, Tween 80 worked as well as Triton in stimulating fluoran-
thene degradation, and it was less toxic.
Only a few studies have examined the effectiveness of surfactants in
enhancing the degradation of PAH mixtures (Guha et al., 1998; Tiehm, 1994),
especially where it involves cometabolism (Boonchan et al., 2000). There is
currently no framework upon which to predict surfactant effects in PAH-con-
taminated soils. In the presence of surfactant, Boonchan et al. (2000) found
that
Stenotrophomonas maltophilia
VUN 1,0010s degraded mixtures of PAHs
more quickly in the presence of surfactant than in the absence of surfactant,
and the maximum specific degradation rate of each component from the
mixture was smaller than when it was degraded alone. Similar decreases in
the degradation rate of individual PAHs due to the presence of other PAHs
have been found in the absence of surfactants for mixed cultures (Guha et
al., 1999) and for pseudomonads (Bouchez et al., 1995; Stringfellow and
Aitken, 1995). Further work in this area is necessary to provide a greater
understanding of how surfactants influence the microbial degradation of
mixtures and to make the application of surfactants a standard engineering
tool in biological soil remediation (Volkering et al., 1998). To this end, we
investigated the degradation of mixtures of PAHs by
Sphingomonas paucimo-
bilis
EPA 505 in the presence of the surfactant Tween 80. The degradation of
phenanthrene, fluoranthene, and pyrene together in a mixture in the pres-
ence of Tween 80 has shown that, despite their increased availability to the
microorganisms, a succession of degradation occurs (Luning Prak and Prit-
chard, 2002a). The succession is probably a function of the specificity of the
