Complexation of cadmium by a rhamnolipid biosurfactant.

The potential of microbially-produced surfactants (biosurfactants) to complex heavy metals was investigated in this study. Batch solution studies using a model metal, cadmium, and an anionic monorhamnolipid biosurfactant produced by Pseudomonas aeruginosa ATCC 9027 showed that complexation of the metal and biosurfactantwas rapid and stable and achieved high reductions in the free Cd 2+ concentration. For example 92% of Cd 2+ (0.72 mM) was complexed by 7.3 mM rhamnolipid, and 97% of Cd 2+ (0.36 mM) was complexed by 3.9 mM rhamnolipid. Under the experimental conditions used, the maximum complexation capacity of the rhamnolipid was 0.2 Cd 2+ /rhamnolipid on a molar basis