Using a mixed culture, the effect of nonionic surfactants on
the biodegradation of phenanthrene has been examined,
and the results compared with the values predicted by
a mathematical model. It was concluded from such an
analysis that phenanthrene in the micelles was bioavailable
[40*]. In another system, four surfactants were tested
to determine their effect on pyrene desorption and
degradation by two Pseudomonas strains. Under unsaturated
(but moist) conditions, one surfactant, Witconcol
SN70, stimulated pyrene mineralization, whereas the same
surfactant inhibited pyrene mineralization in soil slurries
[41]. The reasons for the dual effect of the surfactant
are not clear, but it is likely that the formulation of an
appropriate model and the experimental determination of
several parameters to test the model may be necessary to
interpret this observation.