Biodegradation of hydrophobic compounds in the presence of surfactants

A study was conducted to determine the availability of hydrophobic compounds within surfactant micelles for microbial uptake. Several of the surfactants tested were toxic to the test bacteria and prevented biodegradation of biphenyl and phenanthrene at concentrations below the critical micelle concentration (CMC). The rate of biodegradation was reduced at a surfactant concentration above but not below the CMC only when the test bacterium grew on biphenyl in the presence of Triton X-100. This decrease was correlated with the CMC and was more pronounced at a biphenyl concentration of 0.2 μg/ml than at 2.0 μg/ml. Such a correlation was not observed when bacteria grew on 1.0 μg glutamate per ml, even though the rate of glutamate degradation was reduced by Triton X-100. Analysis of the data with a mathematical model suggested that the experimental observations were probably not the consequence of the unavailability to bacteria of biphenyl within Triton X-100 micelles.