Bioavailability and the Use of Surfactants

Significant differences have been fonnd among different organisms (Guerin and Boyd 1992b Crocker et al. 1995), and indeed incorporation of PAHs into micelles may make them less accessible as snbstrates (Volkering et al. 1995). 

The biodegradation of pyrene, chrysene, fluoranthene, benz[a]anthracene, dibenz[a,/t] anthracene, benzo[a]pyrene, and coronene by Stenotrophomonas maltophilia has been studied in the presence of a range of synthetic surfactants (Boonchan et al. 1998). Nonneutral surfactants were toxic, biodegradation was also inhibited by the neutral Igepal CA-630, and the positive enhancement of removal of substrates was generally low—in the range of 10%. 

Dnring degradation of artificial surfactants, the consumption of oxygen may, however, resnlt in diminished PAH degradation (Tiehm et al. 1997), so that snrfactants with lower biodegradability wonld be advantageous from this point of view. 

A lipoprotein surfactant is produced during growth of Pseudomonas marginalis strain PD-14B with succinate, and prevented flocculation of cells in media containing anthracene, acenaphthylene, naphthalene, and chrysene (Burd and Ward 1996). 

Increased removal of phenanthrene from soil columns spiked with the rhamnolipid mixture synthesized by Pseudomonas aeruginosa UG2 has been demonstrated, and shown to depend both on the increased desorption of the substrate and on partitioning into micelles (Noordman et al. 1998). However, the addition of the biosurfactant from the same strain of Pseudomonas aeruginosa UG2 or of sodium dodecyl sulfate had no effect on the rate of biodegradation of anthracene and phenanthrene from a chronically contaminated soil. 

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