Environmental Engineering Reference
In-Depth Information
gram-negative Comamonas testosteroni strain VP44. Three commercially avail-
able nonionic surfactants (Witconol SN-120, Tergitol NP-15, and Tween 80)
were selected for study based on their solubilization potential and suscep-
tibility to microbial degradation (Pennell et al., 1997; Yeh et al., 1998). Of the
three surfactants evaluated, the linear alcohol ethoxylate (Witconol SN-120)
completely inhibited microbial growth of both bacterial strains. In contrast,
both microorganisms achieved substantial growth in solutions containing
polyoxyethylene (20) sorbitan monooleate (Tween 80) as the sole carbon
source, as well as in solutions containing Tween 80 with either biphenyl or
BP a monochlorinated biphenyl (4-CBP). The nonylphenol ethoxylate (Ter-
gitol NP-15) did not inhibit microbial growth when present in solutions
containing either BP or 4-CBP. In addition, Tergitol NP-15 did not support
microbial growth when present in solution as the sole carbon source. Exam-
ples of representative NYO5 and VP44 growth curves in the presence of
Tween 80 and 4-CBP are shown in Figure 6.21. A summary of the experi-
mental results obtained from the growth experiments for both microbial
strains is presented in Table 6.2. Based on these results, Witconol SN-120 was
eliminated from consideration as a surfactant in subsequent experiments.
Tergitol NP-150 was attractive because it did not appear to negatively impact
growth of NY05 and VP44 and would not be utilized as an alternative carbon
source. However, growing concerns over the toxicity of nonylphenol ethox-
ylates in aquatic systems eliminated Tergitol NP-15 from use in the bioreactor
studies (Ahel et al., 1994).
6.4.3 Plasmid stability studies
A matrix of experiments was performed to ascertain whether microorgan-
isms engineered to grow on a particular PCB congener or pathway would
lose that ability if allowed to grow on other substrates, including surfactants.
10
10
1
1
1961 ppm (0.9 mM 4CB)
1839 ppm (0.6 mM 4CB)
1405 ppm (3.9 mM 4CB)
1098 ppm (0.61 mM 4CB)
1071 ppm (0.044 mM 4CB)
814 ppm (0.044 mM 4CB)
BP, 6.6 mM (ref )
1185 ppm (2.1 mM 4CB)
990 ppm (0.7 mM 4CB)
1309 ppm (0.5 mM 4CB)
1309 ppm (0.4 mM 4CB)
BP, 38 mM (ref )
0.1
0.1
0.01
0.01
0
50
100
150
0
50
100
150
Time, hour
Time, hour
Figure 6.21 Examples of growth of NY05 and VP44 on Tween 80 + 4-CB.
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