DISCUSSION
Observation of both tensio-active and emulsifying activities indicated that biosurfactants were produced by 10 of 23 PAHutilizing bacterial strains. This production was observed when cells were grown on soluble substrates, such as mannitol or dextrose, or on poorly soluble PAHs, such as naphthalene or phenanthrene. Our method of strain selection probably ensured resistance to high concentrations of naphthalene, which has been reported to be toxic for many PAH-metabolizing bacteria.