Effect of Rhamnolipids Produced by <i>Pseudomonas aeruginosa </i>UG2 on the Solubilization of Pesticides

Abstract

The ability of a rhamnolipid mixture produced by Pseudomonas aeruginosa UG2 to solubilize the pesticides atrazine, trifluralin, and coumaphos was compared with that of the surfactant Triton X-100. The values of maximum micellar solubilization capacities (Ksupra [mmol pest/mol surf]) for trifluralin and coumaphos in Triton X-100 were double those for the rhamnolipid mixture, whereas atrazine Ksupra value for the rhamnolipid biosurfactant was in the same range as that for the synthetic surfactant. Despite having the second largest Kow value of the three pesticides, coumaphos had the lowest affinity for both surfactant micellar phases. Comparison of values of aqueous-micelle solubilization rate coefficients (kOWM) obtained for trifluralin showed that the pesticide is solubilized at the same rate in both surfactant micellar phases. A much lower value of micellar-aqueous transfer rate coefficient (kOMW) for trifluralin in the rhamnolipid mixture suggests that the pesticide is bound more tightly to the biosurfactant micellar core and diffuses out to the aqueous phase at a lower speed than that observed for the synthetic surfactant. Future research can benefit from this work by studying the effect that micellar solubilization can have on the bioavailability of organic pollutants for microbial uptake.